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BMC Pulmonary Medicine

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Clinical, economic, and humanistic burden of asthma in Canada: a systematic review

BMC Pulmonary Medicine201313:70

https://doi.org/10.1186/1471-2466-13-70

Received: 27 March 2013

Accepted: 28 November 2013

Published: 5 December 2013

Abstract

Background

Asthma, one of the most common chronic respiratory diseases, affects about 3 million Canadians. The objective of this study is to provide a comprehensive evaluation of the published literature that reports on the clinical, economic, and humanistic burden of asthma in Canada.

Methods

A search of the PubMed, EMBASE, and EMCare databases was conducted to identify original research published between 2000 and 2011 on the burden of asthma in Canada. Controlled vocabulary with “asthma” as the main search concept was used. Searches were limited to articles written in English, involving human subjects and restricted to Canada. Articles were selected for inclusion based on predefined criteria like appropriate study design, disease state, and outcome measures. Key data elements, including year and type of research, number of study subjects, characteristics of study population, outcomes evaluated, results, and overall conclusions of the study, were abstracted and tabulated.

Results

Thirty-three of the 570 articles identified by the clinical and economic burden literature searches and 14 of the 309 articles identified by the humanistic burden literature searches met the requirements for inclusion in this review. The included studies highlighted the significant clinical burden of asthma and show high rates of healthcare resource utilization among asthma patients (hospitalizations, ED, physician visits, and prescription medication use). The economic burden is also high, with direct costs ranging from an average annual cost of $366 to $647 per patient and a total annual population-level cost ranging from ~ $46 million in British Columbia to ~ $141 million in Ontario. Indirect costs due to time loss from work, productivity loss, and functional impairment increase the overall burden. Although there is limited research on the humanistic burden of asthma, studies show a high (31%-50%) prevalence of psychological distress and diminished QoL among asthma patients relative to subjects without asthma.

Conclusions

As new therapies for asthma become available, economic evaluations and assessment of clinical and humanistic burden will become increasingly important. This report provides a comprehensive resource for health technology assessment that will assist decision making on asthma treatment selection and management guidelines in Canada.

Keywords

AsthmaLiterature reviewBurden of illnessCostsQuality of life

Background

Asthma, an inflammatory disorder of the airways [1], accounts for roughly 80% of cases of chronic respiratory disease in Canada [2]. It affects more than 3 million Canadians and roughly 235 million people worldwide [3, 4]. According to Statistics Canada, 8.5% of the population aged 12 and older has been diagnosed with asthma [5]. Its prevalence in this country has been increasing over the last 20 years [3]. Worldwide, asthma prevalence rates have been rising on average by 50% every decade [3]. Notably, asthma is the leading cause of hospital admissions in the overall Canadian population [3, 6], the leading cause of absenteeism from school, and the third leading cause of work loss [3]. Each year, there are 146,000 emergency room visits due to asthma attacks in Canada [3]. Asthma is also a major cause of hospitalization [7] among the estimated 13% of Canadian children who suffer from the disease [8].

High prevalence in conjunction with significant asthma-related morbidity leads to a heavy clinico-economic and humanistic burden of asthma in Canada [9, 10]. Healthcare utilization and costs are even higher when management and control of the disease are suboptimal [11]. The direct and indirect costs associated with asthma are expected to rank among the highest for chronic diseases due to the significant healthcare utilization associated with the disease [9] and asthma’s detrimental impact on physical, emotional, social, and professional lives of sufferers [12].

This systematic review is the first to consolidate and summarize the literature (from 2000–2011) encompassing not only the clinical and economic, but also the humanistic burden of asthma in Canada. It, thus, provides a holistic overview of the weight this disease poses to the healthcare system, patients and society. Specifically, this systematic literature review unveils the direct and indirect costs of asthma per patient, the key drivers of healthcare resource utilization, and the humanistic impact of asthma on patients’ quality of life (QoL), which cannot be inferred from clinical measures [13]. This information, consolidated in a single review, can be of value to payers, policy makers and healthcare providers in making decisions pertaining to the management and treatment of asthma.

Methods

We conducted a search of the PubMed, EMBASE, and EMCare databases to identify original research (cross-sectional, observational, or longitudinal studies on the burden-of-illness and cost-of-illness) published from 2000 to 2011 on the burden of asthma in Canada. Review articles, letters, editorials, commentaries, studies reporting summaries of meeting proceedings or conferences, abstracts or posters presented at scientific meetings, and studies assessing the efficacy or effectiveness of specific interventions were not included. The time frame was selected to reflect more recent developments in the treatment and management of asthma in Canada.

Each search was conducted using controlled vocabulary and key words, with “asthma” as the main search concept. Search terms included “Canada,” “cost of illness,” “hospitalization,” “utilization,” “burden of illness,” “quality of life,” “sickness impact profile,” and “healthcare cost.” Appendix shows the detailed search strategies for each topic area. Searches were limited to articles published in English and studies involving humans. Studies were restricted to Canada.

Titles and abstracts of articles identified were carefully screened in the initial review for relevance to the topic. At the second review, articles were selected for inclusion based on predefined acceptance criteria, which included relevant patient population (ie, adults/children diagnosed with asthma) and appropriate study design and outcome measures (patient- and population-level). Two independent reviewers determined whether studies met the inclusion criteria, and discrepancies between reviewer decisions were resolved in consensus.

Reasons for study exclusions were recorded. For articles that met predefined inclusion/exclusion criteria, the quality of the studies was assessed using methodological checklists provided in the NICE Guidelines Manual [14] and the STROBE (STrengthening the Reporting of OBservational studies in Epidemiology) guidelines [15, 16]. Key data elements were abstracted and tabulated in summary tables: year and type of study, number of study subjects, asthma definition, characteristics of study population, outcomes evaluated, results, and overall conclusions of the study.

Reported costs were inflated to 2011 Canadian dollars (CAD) using the Consumer Price Index from Statistics Canada [17].

Results

Figure 1 depicts the step-by-step study selection process. The MEDLINE, EMBASE, and EMCare database searches yielded 320 citations, 230 citations, and 20 citations, respectively.
Figure 1

Process for studies to be included in the review.

In the first-level selection process (based on the information presented in the article abstracts) for the clinico-economic burden, 503 of the 570 citations were rejected: 174 reported inappropriate outcomes (i.e., outcomes that were not aligned with the outcomes of interest), 150 due to inappropriate disease state (eg, the studies focused on other chronic respiratory diseases or included only a small number of the subjects with asthma), and 91 due to inappropriate study design. Other reasons for rejection during the first-level selection process are shown in Figure 1. Of the 67 full-text articles retrieved for potential inclusion, 34 were excluded during the second-level selection process (28 due to inappropriate outcomes). Thus, 33 articles fulfilled all criteria and were included in the clinico-economic burden review (Figure 1).

After duplicates were removed, 309 studies were identified by the humanistic burden literature searches from the 3 databases. Of these, 288 studies were excluded during the first-level selection for inappropriate disease state (n = 44), inappropriate outcome measure (n = 60), inappropriate study design (n = 96), jurisdiction (n = 9), inappropriate patient population (n = 14), treatment comparator (n = 26), because data could not be extracted in the required format (n = 38), or because they were duplicate studies (n = 1).Twenty-one studies were selected for potential inclusion in the review. During the second-level selection, full-text articles were reviewed and a further 7 were excluded for inappropriate outcome measure (n = 1), study design (n = 2) or jurisdiction (n = 4). Fourteen articles fulfilled all criteria and were included in the humanistic burden review (Figure 1).

Table 1 depicts the quality assessment of the articles on clinical, economic, and humanistic burden using STROBE tools, and Table 2 summarizes quality assessment of the articles on clinical burden using the NICE RCT assessment tool.
Table 1

Summary of quality assessment (using STROBE assessment tools) of the articles included

Report section

Item

Item #

% articles with STROBE criteria not met

Clinical burden

Economic burden

Humanistic burden

Title and abstract

Title

1a

20%

40%

10%

Abstract

1b

13%

30%

0%

Introduction

Background/rationale

2

0%

0%

0%

Objective

3

0%

0%

0%

Methods

Study design

4

3%

10%

0%

Setting

5

0%

0%

0%

Participants

6a

13%

10%

0%

6b

30%

10%

10%

Variables

7

23%

30%

30%

Data sources/measurement

8

10%

10%

0%

Bias

9

53%

40%

40%

Study size

10

20%

30%

30%

Quantitative variables

11

13%

20%

20%

Statistical methods

12a

30%

30%

10%

12b

47%

60%

20%

12c

70%

60%

50%

12d

60%

60%

30%

12e

77%

50%

80%

Results

Participants

13a

40%

50%

30%

13b

63%

60%

30%

13c

73%

80%

50%

Descriptive data

14a

37%

50%

20%

14b

77%

80%

60%

14c

27%

20%

20%

Outcome data

15

3%

10%

0%

Main results

16a

27%

30%

0%

16b

63%

70%

20%

16c

40%

70%

30%

Other analyses

17

37%

20%

60%

Discussion

Key results

18

0%

0%

0%

Limitations

19

7%

20%

20%

Interpretation

20

3%

10%

0%

Generalizability

21

3%

10%

20%

Other

Funding

22

23%

40%

20%

Table 2

Summary of quality assessment (using NICE RCT assessment tool) of the articles included

Type of bias

Humanistic burden (n=4)

Low risk

Unclear risk

Selection

2

2

Performance

3

1

Attrition

2

2

Detection

3

1

Clinical burden studies

Overview

Of the 33 studies meeting all criteria for inclusion, 23 contained clinical burden data only, 7 had information on both clinical and economic burden of asthma, and 3 had data on the economic burden of asthma only.

Of the 30 studies on clinical burden, 1 was a case–control, 22 were cohort, and 7 were cross-sectional studies. Characteristics of studies reporting on clinical burden are shown in Table 3.
Table 3

Characteristics of clinical burden studies included in the review

Reference/Study period

Data source

Study objective

Inclusion criteria

Asthma definition

Retrospective cohort studies

Sadatsafavi et al. 2010 [10] 1996 - 2000

Administrative healthcare data

Determine direct medical costs of asthma-related healthcare in British Columbia

5 to 55 years

Narrow: ICD-9 493.x Broad: visits for an asthma-related diagnosis; hospitalizations with asthma among the discharge diagnoses

≥4 asthma prescriptions in 1 year

≥1 asthma hospitalization

≥2 physician visits for asthma

Blais et al. 2011 [18] 1998 - 2005

RAMQ database,

Determine relationship between better use of LTRA and asthma exacerbations in children

5-15 years

Moderate or severe asthma exacerbations - an ED visit for asthma, a hospital admission for asthma, or a dispensed short-course (14 days) prescription of oral corticosteroids

Diagnosed asthma

Initiating (mono)therapy with ICS or LTRA

Rosychuk et al. 2010 [19] Apr 1999 to Mar 2005

Provincial administrative healthcare databases

Describe the epidemiology of asthma presentations to EDs for 3 main regions in the province of Alberta

All people registered under the AHCIP at any time in a given year

ICD-9 code 493.x or ICD-10 code J45.x as the first or second diagnosis fields in the ACCS

Crighton et al. 2001 [20] Apr 1, 1988 to Mar 31, 2000

DAD database at CIHI,

Examine the seasonal patterns and trends of asthma hospitalizations in relation to age and gender

NR

ICD-9-CM code 493

Ungar et al. 2011 [21] Nov 1, 2000 to Mar 31, 2003

Interview data linked to administrative healthcare data.

Identify factors associated with asthma exacerbation causing ED visits or hospitalizations related to health status, socioeconomic status (SES), and drug insurance

1 to 18 years

Physician-diagnosed asthma; ICD-9 493 or ICD-10 J45

Disano et al. 2010 [22] 2003 - 2006

DAD database from CIHI, INSQP Deprivation Index, Statistics Canada Community Profiles

Examine inequalities between SES groups with respect to rates of ACSC-hospitalizations

Acute care cases of 0 to 75 years; asthma in children for age <20 years

NR

Blais et al. 2009 [18] 2002 - 2004

RAMQ database

Compare the use of healthcare services between new users of budesonide/formoterol and F/S

Asthma patients aged 16 to 65 years ≥1 claim for combination therapy in 2002 or 2003 and no claims for combination therapy for ≥1 year prior to first claim

ICD-9 codes 493.0, 493.1, 493.9

Rowe et al. 2009 [23] 1 Apr 1999–31 Mar 2005

ACCS and other provincial databases.

Describe the epidemiology of asthma presentations to EDs made by adults in the province of Alberta, Canada

Asthmatic individuals aged 18 years

ICD-9 493.x or ICD-10 J45.x

To et al. 2008 [24] 1994 - 1998

DAD database from CIHI, OHIP records, RPDB database

Describe the prevalence of asthma; all-cause mortality; physician visits and hospitalizations for asthma and all causes; and seasonal and geographical variation of healthcare utilization in children

Children aged 0 to 9 years

At least 1 asthma hospitalization or 2 asthma OHIP claims within 3 years

Lemiere et al. 2007 [25] 2001 - 2004

RAMQ database, WRA patients

Compare clinical characteristics and use of medical resources between subjects with OA, WEA, and WRA

NR

Physician-diagnosed asthma OA, WEA, and WRA

To et al. 2007 [26] 1994 to 2006

HMDB database from CIHI, OHIP records, RPDB database;

Examine and predict the persistence of childhood asthma

Children born in 1994 diagnosed with asthma before their 6th birthday, followed up until their 12th birthday

1 asthma hospitalization or 2 asthma physician claims within 3 years prior to age 6 years (ICD-9 493 or ICD-10 J45). Persistent asthma - additional claims during follow-up Remission asthma - no additional claims

Agha et al. 2007 [27] 1993 - 2001

DAD database at CIHI, SES from the 1996 Census data

Examine socioeconomic disparities in ACS and non-ACS admissions among birth cohorts in a universal health insurance setting

Children born alive in Toronto during 1993–2001

The most responsible diagnosis in the CIHI DAD DB

Gershon et al. 2007 [2] 1994/95 to 2001/202

DAD from CIHI, OHIP

Understand the burden of asthma

Asthma patients from ON, aged 0–39 years

1 DAD hospitalization record or 2 OHIP claims for asthma in a 3-year period

Lougheed et al. 2006 [28] 2001 - 2002

CIHI

Assess regional differences in ED visit rates and hospitalizations for asthma

ED visits for asthma

ICD-10 code J45.x

Dik et al. 2006 [29] 1985 - 1998

Manitoba administrative healthcare data

Study 14-year trends in utilization of physician resources for asthma and compare them to trends for allergic rhinitis

NR

ICD-9-CM code 493

Sin et al. 2001 [30] FY 1992 - 1996

CIHI, drug claims, physician billing, and mortality databases

Determine the impact of ICS on rehospitalization for asthma and all-cause mortality rates in elderly patients

Asthmatic patients, aged ≥65 years, who had been hospitalized with a most responsible diagnosis of asthma in the past 5 years

ICD-9 codes 493.0, 493.1, and 493.9

Prospective cohort studies

Rowe et al. 2010 [31] 2004 – 2005

Interviews

Describe factors associated with admission to hospital for acute asthma after ED treatment

Patients aged 18 to 55 years diagnosed with asthma

Patient-reported

Sin et al. 2003 [32] 1985, 1988

AHCIP data,

Determine the relationship between SES and ED visits for asthma in a free access healthcare system.

Children born 1985 to 1988 followed for 10 years

ICD-9 code 493.x

Ungar et al. 2001 [33] May - Oct 1995

Telephone interviews at 1, 3, and 6 months,

Assess the cost of asthma care at the patient level in children from the perspectives of society, the Ontario Ministry of Health, and the patient.

Patients or caregivers filling prescriptions for bronchial inhalers

Probable asthma - a prescription for a bronchial inhaler medication in the last month (bronchodilator or corticosteroid) and reported experiencing shortness of breath, wheeze, or recurrent cough in the past

Anis et al. 2000 [34] Sept 1, 1994 - Aug 31 1995

Hospital ED, telephone interview for follow-up

Estimate the average direct cost of illness for 4 cardiorespiratory conditions

ED visitors who completed follow-up interviews

ED visit records

Rowe et al. 2007 [23] 1996-1998

Structured ED interview and telephone follow-up 2 weeks later

Compare ED asthma management and outcomesbetween Canada and US

Patients aged 2 to 54 years who presented with acute asthma in ED

NR

Cross-sectional studies

Boulet et al. 2008 [35] April - August 2004,

Telephone survey

Assess the influence of current and former smoking on self-reported asthma control and healthcare use

Adults aged 18 to 54 years with physician-diagnosed asthma for ≥6 months

Patient-reported or physician-diagnosed asthma

Klomp et al. 2008 [36] 2002/03 and 2003/04

Health databases in Saskatchewan

Describe the quality of asthma care using a set of proposed quality indicators

Saskatchewan residents who had a valid health insurance number

Over 1-year period: ≥3 prescriptions for antiasthma drug or ≥2 physician claims (ICD-9 code 493) or ≥2 hospitalization claims (ICD-9 493.x or ICD-10 J45.x) or ≥1 claim for physician services or hospitalization for asthma plus ≥1 pharmacy claim for an antiasthma drug

Iron et al. 2003 [37] 1994/1995

CNPHS data, OHIP

Determine the association between demographics, access to care, SES, and need (comorbidities) with actual family physician costs

Survey respondents aged ≥25 years consenting to share HC# and responses with MOHLTC

Self-reported

Anis et al. 2001 [38] 1995

Ministry of Health administrative databases

Determine whether excessive use of SABA, in conjunction with underuse of ICS, would be a marker for poorly controlled asthma and excessive use of healthcare resources

Asthma patients aged 5 to 50 years for whom ≥1 prescription for a SABA was filled in 1995

Patients filling SABA prescriptions; for hospitalizations, ICD-9 code 08 (diseases of the respiratory system)

Baibergenova et al. 2005 [39] April 1, 2001 to March 31, 2004

 

Examine the pattern and strength of seasonal fluctuations in ED visits due to asthma

Asthma patients with ED visits for asthma or status asthmaticus

ICD-9 code 493.x or ICD-10 J45.0–J45.9

Lynd et al. 2004 [40] NR

Survey

Assess the association between SES and SABA use, controlling for asthma severity

Asthmatic patients aged 19 to 50 years residing in the Greater Vancouver Regional District of British Columbia

NR

Case–control study

Suissa et al. 2002 [41] 1975 - 1997

Saskatchewan Health DB

Assess whether regular use of ICS prevents asthma hospitalizations

Source cohort: subjects aged 5–44 years receiving ≥3 prescriptions of an antiasthma medication in any 1-year period Full cohort: all subjects with ≥1 year follow-up, irrespective of whether they were admitted to hospital for asthma during the baseline year

Primary discharge diagnosis of asthma (ICD-9 codes 493.0, 493.1, or 493.9)

Health economic analysis

Seung et al. 2005 [42] 2004

NACRS at CIHI, OCCI, MOHLTC billing

Determine the use of urgent care resources and annual costs for the uncontrolled asthmatic population in Canada

NR

ICD-9 Code 493

ACCS=ambulatory care classification system, ACSC=ambulatory care-sensitive conditions, AHCIP=Alberta Healthcare Insurance Plan, CIHI=Canadian Institute for Health Information, CNPHS=Canadian National Population Health Survey, DAD=Discharge Abstract Database, ED=emergency department, HMDB=Hospital Morbidity Database, ICS=inhaled corticosteroid, ICD=International Classification of Diseases, LTRA=leukotriene receptor antagonist, MOHLTC=Ministry of Health and Long Term Care, NACRS=National Ambulatory Care System, NR=not reported, OA= occupational asthma, OCCI=Ontario Case Costing Initiative, OHIP=Ontario Health Insurance Plan, RAMQ=Régie de l’assurance maladie du Québec, RPDB=Registered Persons Database, SES=socioeconomic status, WEA=work-exacerbated asthma, WRA=work-related asthma.

Most studies clearly reported the study design (97%), setting (100%), participants (87%), and statistical methods employed (70%). However, less than half reported on potential sources of bias and confounding factors or how missing data was handled. Furthermore, less than half of the studies reported on how loss to follow-up was addressed in both the methods and results sections, or how sensitivity analyses were conducted. Main results for outcomes data were appropriately reported in 97 % of the clinical burden studies, and more than 90% met the STROBE criteria for appropriate quality discussion. Most (77%) gave the source of study funding and the roles of the funders. (Tables 1 and 2).

Studies employed a variety of definitions for asthma, including ICD codes, physician visits and/or hospitalizations for asthma (based on billing codes), asthma medication prescriptions filled, and patient self-report. We report the definitions used, but these definitions were not reconciled in this review. When asthma was defined by the presence of ICD codes, it was considered to be narrowly defined, whereas a broad asthma definition included visits for an asthma-related diagnosis and asthma-related hospitalizations among the discharge diagnoses.

Key findings on clinical burden

Hospitalizations

Table 4 provides an overview of hospitalization rates for adult and pediatric patients with asthma in Canada. Reported rates of hospitalization for asthma varied widely according to age, geographic region, gender, and asthma medication use. In a large cohort study spanning over 20 years, Suissa et al. [41] obtained data from the Saskatchewan Health databases on asthma patients from that province aged 5–44 between 1975 and 1991 and found that the overall rate of asthma hospitalization was 42 per 1000 asthma patients per year in patients with at least 1 year of follow-up. The rate was higher (48 per 1000) in patients receiving at least 3 anti-asthma medication prescriptions in any 1 year. During the variable follow-up period (up to 4 years), regular use of inhaled corticosteroids (ICS) was associated with a 31% reduction in the rate of hospital admissions for asthma and a 39% reduction in the rate of readmissions for the cohort with more severe asthma who had been previously hospitalized for the condition during the 1-year baseline period. The study investigators concluded that their findings emphasize the importance of regular use of inhaled corticosteroids to avoid hospitalizations.
Table 4

Rate of hospitalizations for asthma patients in Canada

Study

Number of patients

Patient descriptor

Year

Hospitalizations for asthma

Per patient per year

Per 1000 patients per year

Children

Blais et al. 2011 [43]

7,494

≥1 exacerbations in the year prior to treatment initiation, ICS

1998-2005

0.03

 

≥1 exacerbations in the year prior to treatment initiation, LTRA

0.06

 

19,861

No exacerbation in the year prior to treatment initiation: ICS

0.005

 

No exacerbation in the year prior to treatment initiation: LTRA

0.003

 

Ungar et al. 2011 [21]

490

Asthmatic children

2000-2003

0.25§

 

To et al. 2008 [24]

56,737

0-2 years

1998/1999

 

86.7

99,163

3-5 years

 

27.3

141,305

6-9 years

 

10.9

297,205

Overall

 

30.9

To et al. 2007 [26]

34,216

Persistent asthma

1994-2006

 

63*

Remission asthma

 

39*

Overall

 

52*

Ungar et al. 2001 [33]

339

Asthma children

1995

1

 

Adults

Sadatsafavi et al. 2010 [10]

158,516

Narrow asthma definition€

1996-2000

0.016

 

Broad asthma definition¥

0.03

 

Lemiere et al. 2007 [25]

351 (WEA: 145, OA: 206)

WRA

2001-2003

0.04(0.2)

 

NWRA

0.008(0.7)

 

Anis et al. 2001 [38]

4,671

Appropriate use†

1995

0.07(0.34)

 

763

Inappropriate use‡

0.11(0.42)

 

All ages

Disano et al. 2010 [22]

NR

High SES

2003-2006

 

1.61**

Average SES

 

1.95**

Low SES

 

2.7**

Klomp et al. 2008 [36]

24,616 (24,180 of whom were still alive and living in the region the following year)

Asthma patients

2002/2003 and 2003/2004

 

10.9

Lougheed et al. 2006 [28]

574,304 children and 1,194,095 adults in Ontario

Patients with an ED disposition diagnosis of asthma in a stratified sample of 16 hospitals

2001-2002

 

108 (10.8%) children; 69 (6.9%) adults

Suissa et al. 2002 [41]

30,569

Source cohort††

1975-1997

 

48

4,673

Full cohort‡‡

 

42.4

Seung et al. 2005 [42]

NR

Asthma patients

2004

 

1.43**

§Calculated as 124 hospitalizations for 490 patients.

*Calculated as the rate per 100 patients x 10.

**Calculated as (the rate per 100,000 patients) / 100.

€Narrow asthma definition: ICD-9 493.x.

¥Broad asthma definition: visits for an asthma-related diagnosis; hospitalizations with asthma among the discharge diagnoses.

†Appropriate use (low-dose SABA + high-dose ICS).

‡Inappropriate use (high-dose SABA + low-dose ICS).

††Source cohort: subjects 5–44 years receiving ≥3 prescriptions of an anti-asthma medication (beclomethasone, budesonide, epinephrine bitartrate, fenoterol, flunisolide, ipratropium bromide, isoproterenol, ketotifen, metaproterenol, nedocromil, procaterol, salbutamol, sodium cromoglycate, terbutaline, triamcinolone acetate, or any compound of theophylline) in any 1 year period.

‡‡Full cohort: all subjects with at least 1 year follow up, irrespective of whether or not they were admitted to hospital for asthma during the baseline year.

NWRA=non-work-related asthma; WRA=work-related asthma.

In a retrospective cross-sectional study of asthma patients aged 5–54 years using health databases in Saskatchewan, Klomp et al. [36] found that, in 2002–03 and 2003–04, the hospitalization rate for asthma was 10.9 per 1000 patients per year.

Agha et al. [27], using data on hospital admissions from the Dischrage Abstract Database of the Canadian Institute for Health Information, reported 8,583 asthma hospitalizations among 255,284 pediatric patients (a rate of 33.6 in 1000 patients) born between 1993 and 2000 in Toronto.

A significantly lower rate was reported in Canada by Seung et al. [42], who cited figures reported by the Public Health Agency of Canada of 143 asthma-related hospitalizations per 100,000 adult and pediatric patients, or 1.43 in 1000, in 1998 (with an additional 3.7 per 1000, many of whom had underlying asthma, hospitalized for influenza/pneumonia).

Higher rates were reported for hospital admissions of patients who initially presented to the emergency department (ED). Lougheed et al. [28] reported that 6.9% of adults and 10.8% of children who presented to the ED with asthma were admitted to the hospital.

According to the results of a study based on interviews with parents, 25% of the pediatric study population (124 of 490 patients) had been hospitalized for asthma in the previous 12 months [21]. In a large study utilizing data from Quebec administrative databases, children aged 5 to 15 years with at least 1 exacerbation in the year prior to treatment initiation with ICS or leukotriene receptor antagonists (LTRA) had higher rates of hospitalizations than those with no exacerbation in the previous year (0.03 vs. 0.005 hospitalizations per patient per year in the ICS group and 0.06 vs. 0.003 per patient per year in the LTRA group) [43]. The proportion of prescribed days covered was significantly higher in the LTRA group than in the ICS group (52% vs. 34%) [43].

In a study of all Ontario babies born during the year 1994 who were diagnosed with asthma before their sixth birthday, there was a decreasing trend in hospitalization rates with age, from 86.7 per 1000 patients per year in the 0 to 2 years age group to 27.3 per 1000 patients for those aged 3 to 5 years and 10.9 per 1000 for those aged 6 to 9 years. These investigators also found that children with persistent asthma had more than one and a half times higher hospitalization rates compared with patients whose asthma was in remission (63 per 1000 patients vs. 39 per 1000 patients per year) [26].

In another Ontario-based study that examined asthma seasonality and hospitalizations by gender and age group over a 12-year period, results of spectral analysis revealed that hospitalization rates for children with asthma were highest in September and October each year across the 12-year period, with a 2 to 3-times higher rate of hospitalizations in boys (180 per 100,000) than in girls under the age of 9 years [20]. However, among children older than 9 years, female hospitalizations exceeded those of males [20].

The large variations in reported rates of hospitalizations may be due to variations in ED visit rates and/or hospital admission percentages [28]. Hospital admissions appear to follow a bimodal age distribution pattern, with the very young and the elderly more likely to be admitted [28]. Other factors that can drive up rates of hospitalization in particular regions or among specific populations are higher disease prevalence, greater disease severity, multiple comorbidities, and barriers to care associated with socioeconomic status [27].

ED visits

The number of asthma emergency visits varied by age, type of treatment, social status, and living area (urban/non-urban). Table 5 summarizes ranges and mean numbers of annual ED visits for asthma, as reported in the included studies. According to several studies, both children and adults with asthma averaged less than 1 ED visit per patient per year [21, 23, 28]. ED visit rates were significantly higher in women than in men and, overall, the rate of ED visits increased with age [28].
Table 5

Annual number of ED visits for asthma, per patient, in Canada

Reference

Number of patients

Descriptor

Annual mean number (SD) of ED visits per patient for asthma (range)

From

To

Children

Blais et al. 2011 [43]

27,355

Children, 5–15 years, on ICS or LTRA therapy, by # of exacerbations in the previous year, 1998-2005

0.04* (on LTRA, no exacerb. in the previous year)

0.32* (on ICS, 1+ exacerb. in the previous year)

Lougheed et al. 2006 [28]

4,674

Ontario patients, <20 years, 2001-2002

13.6 [8.7 to 25.2]**

Sin et al. 2003 [32]

90,845

Children, 0–10 years, 1985–1988, by SES

6 [0 to 31]** (very poor)

7 [0 to 34]** (non-poor)

Ungar et al. 2001 [33]

339

Children with asthma, <15 years, Ontario, 1995

0.8*

Adults

Sin et al. 2001 [44]

 

elderly asthmatic, by ICS therapy

1 (1.2)* (not using ICS)

1.5 (1.3)* (using ICS)

Rowe et al. 2009 [45]

48,942

Adults, 1999/2000 to 2004/2005

6.7** (2004/2005)

9.7** (1999/2000)

Lemiere et al. 2007 [25]

351

Adults, work-related asthma, 2001-2004

0.2 (0.7)* (NWRA)

0.3 (0.8)* (WRA)

Lougheed et al. 2006 [28]

3,993

Adults, ≥20 years, 2001-2002

3.9 [1.7 to 10.1]**

Anis et al. 2001 [38]

5,434

Adults, use of SABA+ICS, 1995

0.04 (0.26)* (appropriate use∫)

0.08 (0.33)* (inappropriate use∫)

Rowe et al. 2007 [23]

3,031

Canada and US ED visits, 1996-1998

0(0–3)§ (US)

1(0–3)§ (Canada)

Baibergenova et al. 2005 [39]

73,566

Adult, Ontario, 2001-2004

0.45

All ages

Rosychuk et al. 2010 [19]

21,700

Asthma patients, Alberta, 2004-2005

6.9(6.6-7.0)*** (Calgary)

15.1(15.1-15.9)*** (NMU)

*Per patient.

**Mean [range] per 1000 patients.

***Mean (95%CI).

§Median (IQR).

∫Appropriate use (low-dose SABA + high-dose ICS); Inappropriate use (high-dose SABA + low-dose ICS).

†Calculated from 99,054 ED visits due to asthma were made by 73,566 adults.

ICS=inhaled corticosteroid, LTRA=leukotriene receptor antagonist, NMU= non-major urban areas, NWRA=non-work-related asthma, SABA=short-acting β-agonist, WRA=work-related asthma.

In a study investigating the impact of appropriate use (according to the 1999 Canadian asthma consensus report and the National Heart, Lung and Blood Institute Guidelines for the Diagnosis and Management of Asthma) and compliance with asthma medications in adults, the rate of ED visits for asthma was twice as high for patients not using asthma medication appropriately (high-dose SABA plus low-dose ICS) than for those using it appropriately (low-dose SABA plus high-dose ICS) [38].

Rosychuk et al. [19] examined trends in asthma-related ED visits by more than 45,000 children aged <18 years during the period from April 1999 to March 2005 and did not observe decreased ED presentation rates over time, despite improvements in treatment and availability of guidelines. The standardized rates remained stable over time, with 21.1 visits occurring per 1000 patients in 1999/2000 versus 19.8 per 1000 in 2004/2005.

Sin et al. [30, 44] reported that elderly asthmatic patients using ICS post-discharge from hospital were 29% less likely to be readmitted to hospital for asthma and 39% less likely to experience all-cause mortality compared with those who did not receive ICS post-discharge over a 1-year follow-up period. When age, sex, comorbidity, and use of other antiasthma medications were controlled for, ICS use was associated with a 32% relative rate reduction for recurrent hospitalization or all-cause mortality (95% CI 23%-39%). Among patients who received at least 1 prescription for ICS within 1 year prior to the index hospitalization, the use of ICS 90 days post-discharge was associated with a 41% decrease in recurrent asthma-related hospitalizations or deaths compared with non-use of ICS (95% CI 32%-49%).

Sin et al. [32] also reported on ED visits in children born in Alberta between 1985 and 1988, stratified by SES, and found that very poor children were 23% more likely to have had an ED visit for asthma compared with children from non-poor families (RR 1.23; 95% CI 1.14 – 1.33). Very poor children had a similar risk of having an asthma-related ED visit as poor children (RR 0.97; 95% CI 0.91 – 1.04).

Physician visits

Studies that reported rates of asthma-related physician visits are summarized in Table 6. In a population-based study evaluating 14-year trends in Manitoba in utilization of physician resources for asthma, Dik et al. [29] found that, between the period 1985–1988 and 1994–1998, the greatest increases in prevalence and incidence of physician visits for asthma occurred in the youngest age groups, while in adults the prevalence and incidence changed little with time. However, the average rate of physician visits for asthma decreased from 1.66 visits per patient-year in 1985–1988 to 1.40 in 1989–1993, and further to 1.16 visits per patient-year in 1994–1998.
Table 6

Rate of physician visits in Canada

Study

Number of patients

Patient descriptor

Year

Physician visits for asthma§

Children

To et al. 2008 [24]

56,737

0-2 years

1998/1999

2.2

99,163

3-5 years

1.1

141,305

6-9 years

0.8

297,205

Overall

1.2

Ungar et al. 2001 [33]

339

GP

1995

3.6

Respiratory specialist

2.1

Adults

Boulet et al. 2008 [35]

514

Non-smoker

2004

43% had ≥1

268

Former smoker

49% had ≥1

108

Current smoker

47% had ≥1

Lemiere et al. 2007 [25]

351 (WEA: 145, OA: 206)

WRA

2001-2003

4.1(4.3)

NWRA

1.2(1.7)

Sadatsafavi et al. 2010 [10]

158,516

Narrow asthma definition

1996-2000

1.86

Broad asthma definition

3.85

Iron et al. 2003 [37]

230*

Asthma patients

1994/1995

4.3**

Sin et al. 2001 [44]

6,254

No ICS (elderly)

1992-1996

3.9(2.2)

ICS (elderly)

4(2.2)

Anis et al. 2001 [38]

4,671

Appropriate use†

1995

14.9(15.9)

763

Inappropriate use‡

16.7(19.3)

Anis et al. 2000 [34]

733

Physician visits in ED

1994-1995

1.0(1.3)

Blais et al. 2009 [18]

1264

BUD/FORM

2002-2004

7.5(7.4)

1264

FP/SM

7.3(7)

All ages

Gershon et al. 2007 [2]

NR

All-cause claims

1994/1995

13.2

1995/1996

12.5

1996/1997

12.0

1997/1998

12.1

1998/1999

11.9

1999/2000

11.6

2000/2001

11.5

2001/2002

11.2

§ Per patient per year, mean (SD).

*Asthma patients, calculated as 6% of 3830 NPHS responders.

**Median.

†Appropriate use (low-dose SABA + high-dose ICS).

‡Inappropriate use (high-dose SABA + low-dose ICS).

BUD/FORM=budesonide/formoterol, FP/SM=fluticasone propionate/salmeterol, GP=general practitioner, ICS=inhaled corticosteroid, NR=not reported, NWRA=non-work-related asthma, WRA=work-related asthma.

More former or current smokers than non-smokers visited their physician [35], as did patients with work-related asthma vs. non-work-related asthma [25] and patients inappropriately using their asthma medication [38]. Among elderly patients, the rate of physician visits for asthma was not influenced by treatment with ICS [44].

Children in an Ontario-based study who were born in 1994 and diagnosed with asthma before age 6, and whose asthma persisted until age 11 (as determined by the presence of claims for physician and/or hospital visits between the ages of 6 and 11), had a higher rate of physician visits than those in remission (60 vs. 46.9 visits per 100 patients per year) [26].

Medication prescriptions

Lynd et al. [40] reported that 27% of patients receive oral corticosteroids, 17% use no ICS, 47% receive less than 4 ICS canisters per year, 29% use 5 to 12 canisters, and 8% use more than 12 ICS canisters per year.

Based on available data, children received more prescriptions per patient per year than adults [11, 21, 38]. Patients with inappropriate use of asthma medications (ie, those who were non-adherent to guidelines recommended in the 1999 Canadian asthma consensus report and the National Heart, Lung and Blood Institute Guidelines for the Diagnosis and Management of Asthma) received more than double the number of prescriptions per patient per year (mean [SD] 7.5 [4.9]) compared with those who used asthma medication appropriately (mean [SD] 3.3 [1.9]) [38].

Economic burden studies

Overview

Ten studies evaluated the economic burden of asthma in Canada (5 cohort studies, 4 cross-sectional, and 1 economic analysis). Costs in the economic analysis were calculated for 1,350,871 persons, based on the 1998/1999 estimate that 57% of 2,389,085 persons aged ≥4 years had uncontrolled asthma.

More than 80% of these studies met the STROBE criteria for appropriate quality discussion. Most studies clearly reported the study design (90%), setting (100%), participants (90%), and statistical methods employed (70%). However, less than half reported on potential sources of bias and confounding factors or how missing data was handled and how loss to follow-up was addressed in both the methods and results sections or sensitivity analyses conducted. Most studies (60%) gave the source of funding and the role of the funders for their study (Table 1).

Asthma cases were identified using ICD codes or clearly stated diagnosis, retrospective physician visits, hospitalizations for asthma, and/or asthma medication prescriptions filled or patient self-report of asthma diagnosis or symptoms. There was available evidence on both the direct and indirect components of the economic burden of asthma in Canada. The overall burden varied based on whether studies reported costs from the perspective of an individual patient with asthma or costs at the population level. Few Canadian studies reported a cost per episode of acute asthma, and no studies reported the cost per patients overall. Five studies reported data on the direct costs of asthma at the patient-level. Three of these studies reported asthma costs per asthma patient [10, 24, 37], while 2 studies reported asthma costs per acute asthma episode [34, 42]. Three studies reported population-level direct costs for asthma [10, 24, 42]. Study characteristics are presented in Table 7.
Table 7

Characteristics of economic burden studies included in the review

Reference/Study period

Data source

Study objective

Inclusion criteria

Asthma definition

Retrospective cohort studies

Sadatsafavi et al. 2010 [10] 1996 - 2000

Administrative healthcare data

Determine direct medical costs of asthma-related healthcare in British Columbia

Aged 5 to 55 years

Narrow definition: ICD-9 code 493.x Broad definition: visits for an asthma-related diagnosis; hospitalizations with asthma among the discharge diagnoses

≥4 asthma prescriptions in 1 year

≥1 asthma hospitalization

≥ 2 physician visits for asthma

Malo et al. 2008 [46] 1988 - 2002

Administrative healthcare data,

Assess direct costs of CLI and CFI for OA and their association with selected variables

Subjects receiving compensation for OA

NR

To et al. 2008 [24] 1994 - 1998

DAD database from CIHI, OHIP records, RPDB database

Describe prevalence of asthma, all-cause mortality, physician visits, and hospitalizations for asthma and all causes; seasonal and geographical variation of healthcare utilization in children

Children aged 0–9 years

≥1 asthma hospitalization or 2 asthma OHIP claims within 3 years

Prospective cohort studies

Ungar et al. 2001 [33] May - Oct 1995

Telephone interviews at 1, 3, and 6 months

Assess cost of asthma care at the patient level in children from the perspectives of society, the Ontario Ministry of Health, and the patient

Patients or caregivers filling prescriptions for bronchial inhalers

Probable asthma - a prescription for a bronchial inhaler medication in the last month (bronchodilator or corticosteroid) and reported experiencing shortness of breath, wheeze, or recurrent cough in the past

Anis et al. 2000 [34] Sept 1, 1994 - Aug 31 1995

2 hospital EDs in Saint John, NB; telephone interview for follow-up

Estimate average direct cost of illness for 4 cardiorespiratory conditions

ED visitors who completed follow-up interviews

ED visit records

Cross-sectional studies

Kohen et al. 2010 [47] Fall 1998 and Spring 1999

NLSCY

Examine associations between asthma and school functioning

Individuals aged 7–15 years with complete data on the measures of interest

Past-year wheezing or whistling in the chest and regular use of inhalers

Boulet et al. 2008 [35] April - August 2004,

Telephone survey

Assess influence of current and former smoking on self-reported asthma control and healthcare use

Adults aged 18–54 years with physician-diagnosed asthma for ≥6 months

Patient report of physician-diagnosed asthma

Iron et al. 2003 [37] 1994/1995

CNPHS data linked with OHIP

Determine the association between demographics, access to care, SES, and need (comorbidities) with actual family physician costs

Survey respondents aged ≥25 years consenting to share HC number and responses with MOHLTC

Self-reported

Thanh et al. 2009 [48] 2005

CCHS

To estimate the cost of asthma-related productivity loss days due to absenteeism and presenteeism* in Alberta

Survey respondents aged 18–64 years

Patient report of an asthma diagnosis

Health economic analysis

Seung et al. 2005 [42] 2004

NACRS at CIHI, OCCI, MOHLTC billing

Determine the use of urgent care resources and the annual costs of the uncontrolled asthmatic population in Canada

NR

ICD-9 code 493

* absenteeism=absent from work, presenteeism=at work but not fully functioning.

CCHS= Canadian Community Health Survey, CFI= compensation for functional impairment, CLI=compensation for loss of income, CNPHS=Canadian National Population Health Survey, HC=health card, MOHLTC=Ministry of Health and Long Term Care, NLSCY= National Longitudinal Survey of Children and Youth, OA=occupational asthma, OHIP=Ontario Health Insurance Plan, SES=socioeconomic status.

Key findings on economic burden

All costs reported in this section are in 2011 Canadian dollars.

Patient-level direct costs

Based on data from administrative databases in British Columbia, average total annual direct cost estimates in the general population ranged from $366.17 to $490.88 per asthma patient (Table 8) [10].
Table 8

Summary of studies that reported patient-level total direct costs for asthma

Reference/Study period

Age group

Patient group

Average total annual cost per patient

Inflated 2011 $CAD

Retrospective cohort studies

 

Sadatsafavi et al. 2010 [10] Apr 1996 - Mar 2000

5-55 yrs

Narrow asthma definition

$331.15

$366.17

Broad asthma definition

$443.93

$490.88

To et al. 2008 [24] 1994 - 1998

0-9 yrs

1994/1995

$535.9

$646.95

1995/1996

$458.3

$553.27

1996/1997

$392.6

$473.95

1997/1998

$366.3

$442.20

1998/1999

$332.9

$401.88

Ungar et al. 2001 [33] May - Oct 1995

0-14 yrs

Societal

$1,079

$1,410.17

MOHLTC

$676

$883.48

Patient

$76

$99.33

MOHLTC, Ministry of Health and Long Term Care.

Ungar and colleagues [33] estimated the total cost of asthma in children aged 0–14 years in Ontario to be $883.48 per child from the healthcare perspective (Table 8). Adjusted annual societal costs per patient (1995 Canadian dollars) ranged from $1,122 in children aged 4–14 years to $1,386 in children younger than 4 years. From the Ministry of Health perspective, adjusted annual costs per patient were $663 in children over 4 years and $904 in younger children. Adjusted annual costs from the patient perspective were $132 in children over 4 years and $129 in children under 4 years.

During the period from 1996 – 2000, average hospitalization costs ranged from $67.90 to $136.87 per patient per year in the general population in British Columbia (aged 5 to 55 years), depending on the definition used to categorize asthma-related hospitalizations [10]. The estimated average annual hospitalization cost for asthma in children was $682.21 per patient in Ontario [33].

Sadatsafavi et al. [10] reported that ED visits made by asthma patients in the general population could cost the healthcare system anywhere between $66.35 and $122.09 per visit, depending on the asthma definition used. The reported range of average costs for ED visit per acute asthma episode was $209.48 to $274.48 [10, 33]. Ungar and colleagues [33] estimated the average annual cost for ED visits in children to be $15.68.

The average costs for physician visits per acute asthma episode were estimated to range from $31.72 [34] in an economic modeling study using prospectively collected resource utilization data (9/1/94 to 8/31/95) from hospital emergency department visitors to $31.91 in the economic analysis by Seung and Mittmann [42]. Average costs of $98.02 and $70.57 annually per pediatric patient were reported for family physician and specialist visits, respectively, in the prospective study by Ungar et al. [33]. Although the cost per respiratory specialist visit was higher than the cost per family physician visit ($105.40 vs. $51.40 for the first visit and $23.10 vs. $16.25 for an additional visit), nearly twice as many patients (271, or 80%) reported visiting a family physician, at an average annual use of 3.6, compared with a respiratory specialist (141, or 42% of patients), at an average annual use of 2.1 [33]. A study conducted in Ontario demonstrated that outpatient claim costs for persons with asthma exceeded those for persons without asthma by about $200 per person per year [2].

With regard to asthma medication prescriptions, the administrative database study from British Columbia estimated the average annual cost for asthma medication in the general population to be $231.92 per patient [10]. Ungar et al. [33] estimated the average annual costs for medication per patient in children to be $352.87 from the societal perspective and $86.26 (2011 $CAD) from the patient perspective. Estimated average medication costs per acute asthma episode ranged from $5.29 to $629.39 in these studies [10, 33].

Population-level direct costs

The 1998–1999 healthcare cost for asthmatic children in Ontario ($120 million, or $227.1 - $640.3 per child per year, depending on age group) was considerably higher than the total asthma cost for the general population (all ages) of British Columbia during the period 1996 – 2000 (~$41.8 million, or $331 per patient per year) (Table 9) [10, 24].
Table 9

Summary of studies that reported population-level total direct costs for asthma

Reference/Study period

Age group

Patient group

Total annual population cost

Inflated 2011 $CAD

Retrospective cohort studies

Sadatsafavi et al. 2010 [10] April 1996 - March 2000

5-55 yrs

Narrow asthma definition

$41,858,610

$46,285,583

Broad asthma definition

$56,114,574

$62,049,260

To et al. 2008 [24] 1994 - 1998

0-9 yrs

1994/1995

$116,700,000

$140,882,165

1995/1996

$114,800,000

$138,588,454

1996/1997

$106,900,000

$129,051,443

1997/1998

$105,300,000

$127,119,897

1998/1999

$98,900,000

$119,393,711

MOHLTC, Ministry of Health and Long Term Care.

Based on data from administrative healthcare databases (April 1996 through March 2000), the total annual population-level asthma cost estimates in the general population in British Columbia ranged from ~ $46.3 million to $62.0 million , depending on the definition of asthma used [10]. Between ~8.5 million and ~17.2 million of that was spent on asthma-related hospitalizations, ~8.4 million to ~15.5 million on physician/ED visits, and ~15.4 million to ~29.3 million on asthma medications [10]. Medication costs represented the bulk (63.9%) of the total cost, hospitalizations/ED visits comprised 17.8%, and physician visits accounted for 18.3% of the total cost.

In Ontario, the total population-level costs for asthma in children aged 0–9 years ranged from ~ $140 million during 1994–1995 to ~ $120 million in 1998–1999 [24].

Patient-level indirect costs

About 50% of children missed 1–3 days of school (47.6% in the group with low-severity asthma, 53.9% in those with moderate severity, and 50.6% in the severe asthma group), and 5.7% of the low severity, 5.3% of the moderate severity, and 9.1% of the severe asthma patients were absent for 7 or more days [47].

Malo et al. [46] evaluated a random sample of 8 to 10 accepted claims for occupational asthma per year from 1988 to 2002 in Quebec and found that the mean cost of compensation for loss of income (CLI) across the 15 years (not accounting for inflation) was $72,500 (median $40,700) and the mean cost of compensation for functional impairment (CFI) was $11,700 (median $7,600). Median CLI costs were significantly higher in men than women (69.9 vs 13.1), in workers aged ≥40 years versus those <40 years (90.1 vs 27.4), and in workers taking inhaled steroids at diagnosis (92 vs 52) and at reassessment (81 vs 35). Median CFI costs were significantly higher for individuals being treated with inhaled steroids at the time of diagnosis (14.0 vs 5.2) and reassessment (13 vs 6).

Population-level indirect costs

In a population of ~1.5 million working-age individuals in Alberta with an asthma prevalence of 8.5%, the number of asthma-related productivity lost work days ranged from 441,728 to 533,363 in 1 year, at a cost of $78.1 to $94.4 million in lost productivity [48].

Ungar et al. [49] reported productivity loss days (PLD) without reporting actual indirect costs. They found that annual PLD varied from 12 in employed persons to 20 in students, 22 in homemakers, retirees and the unemployed, and 49 in disability pensioners. Annual PLDs increased with increasing disease severity.

Humanistic burden studies

Overview

Fourteen articles reporting results from 13 studies were retained for inclusion out of the 309 studies identified by the humanistic burden literature search. Two were cohort studies, 8 were cross-sectional, and 4 studies were RCTs. Only 1 of these was a pediatric study [50], which assessed the impact of asthma medication on children using the 3-domain Pediatric Asthma Quality of Life Questionnaire (PAQLQ). No studies were identified that reported utilities or QoL from a caregiver perspective. QoL assessments focused on subgroups of the asthma population, and studies had small numbers of participants. A variety of definitions were used to define asthma including clinical diagnosis, presence of symptoms, and positive inhalation tests. Characteristics of studies reporting on humanistic burden are detailed in Table 10.
Table 10

Characteristics of humanistic burden studies included in the review

Reference/Study period

Design

Study objective

Inclusion criteria

Asthma definition

Miedinger et al. 2011 [51] 2004 - 2006

Longitudinal study - subjects who claimed compensation for OA in Quebec

Examine association between clinical and socioeconomic variables and psychological and cost outcomes in patients with OA

Claimed compensation for OA at CSST, not exposed to offending allergens causing OA for ≥2 years

Workplace-associated respiratory symptoms and positive results in specific inhalation test

Lavoie et al. 2010 [52] NR

Prospective cohort, self-report questionnaires

Assess level of psychological distress and range of disease-relevant emotional and behavioural coping styles in patients with severe vs. moderate asthma

Patients aged 18–69 years recruited from 2 tertiary care outpatient asthma clinics

Standard ATS criteria; Severe asthma - received adequate therapy and verified treatment adherence, with patients meeting ATS major and minor criteria for severe asthma

Bacon et al. 2009 [53] Jun 2003 - Jan 2007

Cross-sectional study; patients administered questionnaires

Assess associations between adult SES (measured according to educational level) and asthma morbidity, including asthma control; asthma-related emergency health service use; asthma self-efficacy, and asthma-related QoL

Patients aged 18–75 years, recruited from outpatient asthma clinic of Hôpital du Sacré-Coeur de Montréal

Physician-diagnosed asthma - charted 20% fall in FEV1 after methacholine challenge and/or bronchodilator reversibility in FEV1 of ≥20% predicted; severity based on GINA guidelines (mild intermittent, mild persistent, moderate persistent, and severe persistent)

McTaggart-Cowan et al. 2008 [54] NR

Cross-sectional - self-administered questionnaire

Evaluate validity of HUI-3, EQ-5D, SF-6D, and AQL-5D to distinguish between different levels of asthma control

Patients aged 19–49 years,no other concurrent respiratory conditions

Self-reported, physician-diagnosed asthma

Rowe et al. 2007 [55] NR

RCT (double-blind) -structured telephone interviews

Examine effect of adding a LABA (salmeterol) to fixed dose of oral prednisone and ICS (fluticasone)

Patients aged 18–55 years, PEF of <80% predicted before treatment, discharged from ED

Clinically diagnosed acute asthma in ED; PEF of <80% predicted before treatment

Yacoub et al. 2007 [56] 2004 - 2006

Retrospective cohort study; questionnaire administered to subjects

Evaluate utility of adding assessment of airway inflammation to standard assessment of impairment in subjects with OA; to evaluate psychological and QoL impact of OA

Workers' Compensation Agency of Quebec claimants

OA claimants

Lavoie et al. 2006 [57] 2003 - 2005

Cross-sectional study; structured psychiatric interview

Evaluate relative impact of having a depressive and/or anxiety disorder on asthma control and QoL

Patients aged 18–75 years with primary diagnosis of asthma

Physician-diagnosed asthma - chart evidence of 20% fall in FEV1 after methacholine challenge and/or bronchodilator reversibility in FEV1 20% predicted; severity classified according to international GINA guidelines

Lavoie et al. 2006 [58] Jun 2003 to Apr 2004

Cross-sectional study; patients completed ACQ and AQLQ questionnaires

Assess BMI in a Canadian sample of asthma outpatients, and evaluate associations between BMI and levels of asthma severity, asthma control, and asthma-related QoL

Patients aged 18–75 years with primary diagnosis of asthma, fluency in either English or French

Physician diagnosed asthma - chart evidence of 20% fall in FEV1 after methacholine challenge and/or bronchodilator reversibility in FEV1 20% predicted; severity classified according to GINA guidelines

Lavoie et al. 2005 [52] NR

Cross-sectional study; patients completed ACQ and AQLQ questionnaires

Evaluate prevalence of psychiatric disorders in adult asthma patients and associations between psychiatric status, levels of asthma control, and asthma-related QoL

Patients aged 18–75 years with primary diagnosis of asthma, fluency in either English or French

Physician diagnosed asthma - confirmed by chart evidence of 20% fall in FEV1 after methacholine challenge and/or bronchodilator reversibility in FEV1 20% predicted; severity classified according to GINA guidelines

Mo et al. 2004 [59] 2000 - 2001

Cross-sectional study; HUI used to measure QoL

Measure HRQL of chronic disease and detect associations between HUI system and various chronic conditions

All household residents aged ≥12 years in all provinces and territories

NR

FitzGerald et al. 2000 [60]

RCT - AQLQ administered to assess QoL

Compare effectiveness of prednisone and budesonide on relapse rate

Patients aged 15–70 years, recruited after discharge from ED after acute asthma exacerbation

Asthma exacerbation - progressive increase in dyspnea and history of asthma as per ATS criteria

Williams et al. 2010 [61] Baseline to week 12

RCT AQLQ data from first 12 weeks of the GOAL study

Compare AQLQ data across 16 countries (17 languages)

Patients aged 12 to <80 years with ≥6-month history of asthma

NR

Miedinger et al. 2011 [51] 2004 to 2006

Cross-sectional study; participants completed validated French versions of QoL questionnaires

Assess correlation between asthma-specific QoL and levels of psychological distress and psychiatric disorders in patients with OA

Patients who claimed compensation for OA at CSST; no longer exposed to sensitizing agents ≥2 years

OA - asthma caused and maintained by conditions attributable to the occupational environment and not to stimuli encountered outside the workplace

Zimmerman et al. 2004 [50] 12-week study

RCT (double-blind); patients administered PAQLQ

Examine efficacy and safety of adding regular formoterol at 2 different doses to maintenance treatment with ICS in children with asthma not optimally treated by ICS alone

Patients aged 6–11 years with clinical diagnosis of asthma as per ATS criteria for ≥6 months; FEV1 50-90% of predicted normal; documented post-bronchodilator reversibility of ≥15%, ≥9% of predicted normal; treatment with regular ICS for ≥3 months before trial entry; asthma symptoms sufficient to suggest additional therapy may be needed; ability to use peak flow meter and Turbuhaler®, able to answer questions from PAQLQ; parent/guardian to complete daily diary

Clinical diagnosis of asthma defined according to ATS criteria; severe asthma exacerbation defined as asthma symptoms requiring oral corticosteroids or increase in dose of ICS as judged by the investigator

ACQ=Asthma Control Questionnaire; AQLQ=Asthma Quality of Life Questionnaire; AQL-5D=Asthma Quality of Life-5D ; ATS=American Thoracic Society; BMI=body mass index; BUD=budesonide; CSST=Commission de la Santé et de la Sécurité du Travail du Québec (Canadian Centre for Occupational Health and Safety); ED=emergency department; EQ-5D =EuroQoL 5-D ; FEV1=forced expiration volume in 1 second; GINA=Global Initiative for Asthma; GOAL=Gaining Optimal Asthma ControL (study); GSCs=glucocorticosteroid; HRQoL = health-related quality of life; HUI=health utilities index; ICS=inhaled corticosteroid; LABA=long-acting β-agonist; NR=not reported; OA=occupational asthma; PAQLQ=Pediatric Asthma Quality of Life Questionnaire; PEF=peak expiratory flow; PRED=prednisone; PRIME-MD=Primary Care Evaluation of Mental Disorders; PSI=Psychiatric Symptom Index; QoL = quality of life; RCT=randomised controlled trial; SES=socioeconomic status; SF-6D=Short-Form 6D; SGRQ=St-Georges Respiratory Questionnaire.

Overall, most studies on humanistic burden met good reporting quality standards in accordance with STROBE criteria (Table 1). However, less than half of the studies reported how missing data and loss to follow-up was handled or sensitivity or other analyses performed. Most studies also met the STROBE criteria for appropriate quality discussion (80%) and reported information on study funding (80%).

The effect of psychiatric disorders on asthma control and QoL in adults was examined in 2 studies [57, 58]. Another 2 studies examined QoL by asthma severity and chronicity [54, 62]. Eleven studies used the 32-item AQLQ to assess the impact of asthma on patients’ QoL [5156, 5863]. Other tools that were used to measure the humanistic burden of asthma were the AQL-5D, the EQ-5D, the SF-6D, the Health Utilities Index (HUI-3), the Asthma Control Questionnaire (ACQ), and the 8-question St Georges Respiratory Questionnaire (SGRQ).

Key findings on humanistic burden

Depression and anxiety were prevalent among asthma patients and were associated with worse asthma control and quality of life (QoL) [52]. Yacoub et al. reported a 50% prevalence of anxiety and/or depression among 40 subjects with occupational asthma [56]. In a study conducted by Lavoie et al., 31% of 504 adults with physician-diagnosed asthma met the diagnostic criteria for 1 or more psychiatric diagnoses [57]. A study specifically looking at occupational asthma also found that psychological distress and psychiatric disorders including depression, anxiety, and dysthymia were associated with impaired QoL [63].

As one would expect, QoL became progressively worse as disease severity increased [54, 62]. Furthermore, QoL was lower in asthma patients who had at least 1 other chronic disease compared to those who had no other chronic disease [54].

A study of 504 consecutive adults with physician-diagnosed asthma reported that depressive and anxiety disorders were both independently associated with decreased health-related QoL (as measured by AQLQ scores), but only depressive disorders were independently associated with worse asthma control (as measured by ACQ scores) [57]. Interestingly, having both depressive and anxiety disorders did not increase the risk for worse asthma control or decreased QoL [57]. According to the study authors, this finding suggests that there is no incremental risk associated with having both a depressive disorder and an anxiety disorder on asthma control and QoL. The researchers also noted that the lack of an independent association between anxiety disorders and asthma control may be due to the fact that patients with anxiety disorder are more inclined to self-monitor their symptoms, and are thus more likely than depressed patients to detect asthma symptoms and seek intervention.

Lavoie et al. [58] studied the association between clinical measures of asthma morbidity and body mass index (BMI), and found that patients with higher BMI scores had worse asthma control and poorer QoL (i.e., higher ACQ and lower AQLQ scores), independent of age, gender, and asthma severity. However, BMI was not associated with asthma severity.

Discussion

This review is the first to summarize the literature encompassing not only the clinical and economic burden of asthma, but also the humanistic burden of asthma in Canada. This systematic review confirms that the burden associated with asthma is substantial, and will undoubtedly become more pronounced as the asthma prevalence increases in Canada. The asthma burden as it is known today can likely be decreased by the development and implementation of innovative treatment strategies in the management of this disease.

A considerable body of literature was included in this systematic review (33 articles for the clinical and economic burden and 14 for the humanistic burden).The reviewed literature suggested that the healthcare resource utilization in asthma varied greatly in Canada by age group and type of treatment used. The substantial clinical burden was reflected by high rates of hospitalizations, ED and physician visits, and medication use. Lower rates of ED visits and hospitalizations, as well as reduced deaths, were observed among ICS users compared with non-users (except among the elderly), but these reductions were not as pronounced in patients who had experienced recent asthma exacerbations.

We collected evidence on both the direct and indirect components of the economic burden of asthma in Canada. The overall burden varied based on whether studies reported costs from the perspective of an individual patient with asthma or costs at the population level. Reported estimates for patient-level total direct costs, inflated to 2011 Canadian dollars, ranged from $99.33 per patient in a cohort of children aged 0–14 years in Ontario (May – October 1995) [33] to $646.95 per patient in a cohort of children aged 0–9 years, also in Ontario (1994/1995) [24]. Reported estimates for population-level total direct costs, inflated to 2011 Canadian dollars, ranged from $46,285,583 for patients aged 5–55 years in British Columbia (April 1996 – March 2000) [10] to $140,882,165 for patients aged 0–9 years in Ontario (1994–1998) [24]. Few Canadian studies reported a cost per episode of acute asthma.

Fourteen studies assessed the impact of asthma on the QoL of patients; however, only 4 reported on QoL of children with asthma, which represents a significant knowledge gap. For the most part, QoL assessments focused on subgroups of the asthma population and studies had small numbers of participants. Asthma was associated with depression and/or anxiety in several studies.

As noted above, these research studies vary considerably in terms of geographic region of study, characteristics of patient populations, study methodologies, and definitions of asthma used, which presents a significant challenge in drawing definitive conclusions from our study. Furthermore, unique findings reported in single studies have yet to be confirmed or refuted by subsequent research. Thus, in our review, results are presented as reported, but no consensus can be reached on the rates of resource utilization among asthmatic patients, asthma-related costs, or the degree of QoL impairment among individuals with asthma.Our study suggests that there is a significant knowledge gap in understanding the comprehensive burden of asthma across Canada.

Nevertheless, the high rates of healthcare resource utilization observed among patients with asthma during this review revealed only the tip of the iceberg. The economic burden is noteworthy, with direct costs – particularly those related to hospitalizations and physician/ED visits – representing the highest proportion of asthma-related costs. The indirect costs mainly due to time loss from work, productivity loss, functional impairment and caregiver time also add to this significant burden. Although there is a paucity of research on the humanistic burden of asthma in Canada, the few studies included in this review indicate that QoL is unquestionably diminished in asthmatic patients and that there is a high prevalence of psychological distress and psychiatric disorders among patients with asthma. Notable knowledge gaps on the humanistic burden of asthma are the lack of QoL assessments in children and caregivers, as well as quantifying the asthma-attributable burden in this patient population.

This systematic review provides a holistic overview of the burden of asthma in Canada, detailing the direct and indirect costs, the key drivers of healthcare resource utilization, and the impact of asthma on patients’ quality of life - information that cannot be inferred from clinical measures. This information can be of value to payers, policy makers and healthcare providers in making decisions pertaining to the management and treatment of asthma.

For example, knowing that depression is often associated with asthma and that its severity and asthma control are intertwined, it might be useful to have psychologists/psychiatric healthcare professionals on the disease management team from the time of asthma diagnosis. Also, findings that BMI levels and asthma control and QoL are related, can lead to adding interventional measures to the treatment strategy.

As far as treatment options go, the use of inhaled corticosteroids was noted in many of the reviewed articles to be associated with lower rates of ED visits and hospitalizations; therefore recommending the appropriate use of medications (low-dose SABA plus high-dose ICS) should be emphasized.

More research in Canada is needed to add to the holistic picture of the impact of this disorder on the lives of patients, their families, and caregivers. Furthermore, much remains to be learned about the optimal use of the currently available treatments, how to combine them for maximal benefit, and how to incorporate new drugs in development into existing treatment regimens.

Limitations

All literature reviews are limited by the publication bias of the articles that are available. We acknowledge the fact that studies identifying a significant burden of asthma may likely be published than the ones reporting a low burden. The articles in this review are limited to the English language, and publication constraints were placed on articles identified by the search with studies limited to those published since 2000. Spatial restrictions were also applied, limiting studies to Canada. Studies employed a variety of defining criteria for asthma (from patient self-report to ICD-codes, from physician-recorded diagnosis to discharge diagnosis combined with medication use), and these definitions were not reconciled in this review. This may have led to underreporting or overreporting of certain outcomes. Results were analyzed as reported, but direct comparisons between studies are lacking, due to the high heterogeneity of methodological approaches.

In spite of these limitations, this review was systematic in nature and summarizes all available and relevant data published since 2000, thus providing a better understanding of the literature with respect to the clinical, economic, and humanistic burden of asthma.

Conclusions

The information contained within this study provides a comprehensive overview of the burden of asthma in Canada. Moreover, our study identifies several key knowledge gaps in understanding this area. As new therapies for asthma become available, health technology assessments will become increasingly important not only as it pertain to amendments to clinical practice guidelines but also with regard to formulating reimbursement decisions. Our study summarizes information that can prove important for physicians, healthcare authorities, and government officials involved in the treatment selection and development of disease management guidelines for asthma.

Appendix

The Appendix tables present the literature search strategies used to retrieve articles reporting on the clinical and economic burden (Table 11) and humanistic burden (Table 12) of asthma. The strategies were applied to the Medline. EmBase and EMCare databases.
Table 11

Clinical and economic burden search strategy

Medline (1996 to present)

1

Asthma[MeSH] OR Asthma [Title,abstract]

71642

2

hospitalisation[MeSH] OR cost of illness[MeSH] OR absenteeism OR ambulatory care/Economics[MeSH] OR drug costs[MeSH] OR emergency medical services/Economics[EMTREE] OR healthcare costs[MeSH] OR nursing services/Economics[MeSH] OR physicians/Economics[MeSH]

77559

3

(burden OR clinical impact OR hospitalisation OR utilization OR burden of illness OR cost$1 OR cost of illness OR utilization OR nursing cost$1 OR physician cost$1 OR physician visit$1).TI,AB.

354392

4

1 AND (2 OR 3)

6208

5

canada OR canadian OR alberta OR british columbia OR manitoba OR new brunswick OR newfoundland NEXT labrador OR northwest territories OR nova scotia OR nunavut OR ontario OR prince edward island OR quebec OR saskatchewan OR yukon NEXT territory

462814

6

4 AND 5 AND LG=English AND HUMAN=YES

430

7

Publication Type=RANDOMIZED CONTROLLED TRIAL

223783

8

6 NOT 7

398

9

limit set 8 YEAR > 1999

324

EmBase (1992 to present)

10

Asthma[EMTREE] OR Asthma[Title,abstract]

100645

11

hospitalisation[EMTREE] OR cost of illness[EMTREE] OR cost[EMTREE] OR absenteeism[EMTREE] OR drug cost[EMTREE] OR healthcare cost[EMTREE] OR nursing cost[EMTREE]

348772

12

(burden OR clinical impact OR hospitalisation OR utilization OR burden of illness OR cost$1 OR cost of illness OR utilization OR nursing cost$1 OR physician cost$1 OR physician visit$1)[Title,abstract]

381230

13

10 AND (11 OR 12)

10735

14

canada OR canadian OR alberta OR british columbia OR manitoba OR new brunswick OR newfoundland NEXT labrador OR northwest territories OR nova scotia OR nunavut OR ontario OR prince edward island OR quebec OR saskatchewan OR yukon NEXT territory

462680

15

13 AND 14 AND LG=English AND HUMAN=YES

654

16

Randomized Controlled Trial[EMTREE] OR Randomized Controlled Trial Topic[EMTREE]

249284

17

15 NOT 16

596

18

limit set 17 YEAR > 1999

515

EMCare

19

Asthma[EMTREE] OR Asthma[Title,abstract]

28554

20

hospitalisation[EMTREE] OR cost of illness[EMTREE] OR cost[EMTREE] OR absenteeism[EMTREE] OR drug cost[EMTREE] OR healthcare cost[EMTREE] OR nursing cost[EMTREE]

152470

21

(burden OR clinical impact OR hospitalisation OR utilization OR burden of illness OR cost$1 OR cost of illness OR utilization OR nursing cost$1 OR physician cost$1 ORphysician visit$1)[Title,abstract]

156234

22

19 AND (20 OR 21)

4228

23

canada OR canadian OR alberta OR british columbia OR manitoba OR new brunswick OR newfoundland NEXT labrador OR northwest territories OR nova scotia OR nunavut OR ontario OR prince edward island OR quebec OR saskatchewan OR yukon NEXT territory

174145

24

22 AND 23 AND LG=EN

312

25

Randomized Controlled Trial[EMTREE] OR Randomized Controlled Trial[EMTREE]

82273

26

24 NOT 25

278

27

limit set 26 YEAR > 1999

222

Medline, EmBase and EMCare combined

28

combined sets 9, 18, 27

1061

29

dropped duplicates from 28

486

30

unique records from 28

575

31

split set 30

320 Medline

32

split set 30

234 EmBase

33

split set 30

21 EmCare

Table 12

Humanistic burden search strategy

Medline

1

Asthma[MeSH] OR Asthma[Title,Abstract]

71642

2

Sickness impact profile[MeSH] OR quality of life[MeSH] OR patient satisfaction[MeSH]

121478

3

(quality of life OR QoL OR patient reported outcome$1 OR patient satisfaction OR emotional satisfaction OR patient dissatisfaction OR patient response OR gratification OR treatment satisfaction OR disability rate$1 OR health related quality of life OR HRQoL OR utilities) [Title,Abstract]

119368

4

1 AND (2 OR 3)

3035

5

canada OR canadian OR alberta OR british columbia OR manitoba OR new brunswick OR newfoundland NEXTlabrador OR northwest territories OR nova scotia OR nunavut OR ontario OR prince edward island OR quebec OR saskatchewan OR yukon NEXT territory

462814

6

4 AND 5 AND LG=English AND HUMAN=YES

172

7

limit set 6 YEAR > 1999

141

EmBase

8

Asthma[EMTREE] OR Asthma[Title,Abstract]

100645

9

Sickness impact profile[EMTREE] OR quality of life[EMTREE] OR patient satisfaction[EMTREE]

199618

10

(quality of life OR QoL OR patient reported outcome$1 OR patient satisfaction OR emotional satisfaction OR patient dissatisfaction OR patient response OR gratification OR treatment satisfaction OR disability rate$1 OR health related quality of life OR HRQoL OR utilities) [Title,Abstract]

124979

11

8 AND (9 OR 10)

5651

12

canada OR canadian OR alberta OR british columbia OR manitoba OR new brunswick OR newfoundland NEXT labrador OR northwest territories OR nova scotia OR nunavut OR Ontario OR prince edward island OR quebec OR saskatchewan OR yukon NEXT territory

462680

13

11 AND 12 AND LG=English AND HUMAN=YES

306

14

limit set 13 YEAR > 1999

267

EMCare

15

Asthma[EMTREE] OR Asthma[Title,Abstract]

28554

16

Sickness impact profile[EMTREE] OR quality of life[EMTREE] OR patient satisfaction[EMTREE]

94595

17

(quality of life OR QoL OR patient reported outcome$1 OR patient satisfaction OR emotional satisfaction OR patient dissatisfaction OR patient response OR gratification OR treatment satisfaction OR disability rate$1 OR health related quality of life OR HRQoL OR utilities) [Title,Abstract]

48206

18

15 AND (16 OR 17)

2178

19

canada OR canadian OR alberta OR british columbia OR manitoba OR new brunswick OR newfoundland NEXT labrador OR northwest territories OR nova scotia OR nunavut OR Ontario OR prince edward island OR quebec OR saskatchewan OR yukon NEXT territory

174145

20

18 AND 19 AND LG=English

137

21

limit set 20 YEAR > 1999

111

Medline, EmBase and EMCare combined

22

combined sets 7, 14, 21

519

23

dropped duplicates from 22

207

24

unique records from 22

312

25

split set 24

141 Medline

26

split set 24

158 EmBase

27

split set 24

13 EMCare

Declarations

Acknowledgments

The authors thank Victoria Porter, medical writer at Optum, for her assistance with the preparation of this manuscript. Financial support for this study was provided by GlaxoSmithKline Inc. Canada.

Authors’ Affiliations

(1)
Medical Affairs, GlaxoSmithKline Canada
(2)
Department of Clinical Epidemiology and Biostatistics, McMaster University
(3)
Product Value Strategy Consulting, Optum
(4)
Medical Affairs, Sanofi

References

  1. Masoli M, Fabian D, Holt S, Beasley R: Global initiative for asthma (GINA) program. Allergy. 2004, 59: 469-78. 10.1111/j.1398-9995.2004.00526.x.View ArticlePubMedGoogle Scholar
  2. Gershon A, Wang C, Cicutto L, To T: The burden of asthma: Can it be eased?. Healthc Q. 2007, 10: 22-4.View ArticlePubMedGoogle Scholar
  3. Asthma Society of Canada: Asthma facts and statistics. 2012, Available at http://www.asthma.ca/corp/newsroom/pdf/asthmastats.pdf Last accessed August 27Google Scholar
  4. Lougheed MD, Lemiere C, Ducharme FM, Licskai C, Dell SD, Rowe BH, Fitzgerald M, Leigh R, Watson W, Boulet LP: Canadian thoracic society asthma clinical assembly: Canadian thoracic society 2012 guideline update: diagnosis and management of asthma in preschoolers, children and adults. Can Respir J. 2012, 19: 127-164.View ArticlePubMedPubMed CentralGoogle Scholar
  5. Statistics Canada: asthma. 2010, website [http://www.statcan.gc.ca/pub/82-625-x/2011001/article/11458-eng.htm ]
  6. To T, Gershon A, Cicutto L, Wang CN: The burden of asthma: can it be eased? The Ontario record. Healthc Q. 2007, 10: 22-4.PubMedGoogle Scholar
  7. Millar WJ, Gerry BH, Statistics Canada: Childhood asthma. Health Rep. 1998, 10: 12-http://www5.statcan.gc.ca/bsolc/olc-cel/olc-cel?catno=82-003-x19980034137&lang=eng.pdf,Google Scholar
  8. Garner R, Kohen D, Statistics Canada: Changes in the prevalence of childhood asthma. Health Rep. 2008, catalogue 82-003-X. http://www.statcan.gc.ca/pub/82-003-x/2008002/article/10551-eng.pdf Google Scholar
  9. Bahadori K, Doyle-Waters MM, Marra C, Lynd L, Alasaly K, Swiston J, FitzGerald JM: Economic burden of asthma: a systematic review. BMC Pulm Med. 2009, 9: 24-10.1186/1471-2466-9-24.View ArticlePubMedPubMed CentralGoogle Scholar
  10. Sadatsafavi M, Lynd L, Marra C, Carleton B, Tan WC, Sullivan S, Fitzgerald JM: Direct health care costs associated with asthma in British Columbia. Can Respir J. 2010, 17: 74-80.View ArticlePubMedPubMed CentralGoogle Scholar
  11. Bousquet J, Bousquet PJ, Godard P, Daures JP: The public health implications of asthma. Bull World Health Organ. 2005, 83: 548-54.PubMedPubMed CentralGoogle Scholar
  12. Braman SS: The global burden of asthma. Chest. 2006, 130: 4S-12S. 10.1378/chest.130.1_suppl.4S.View ArticlePubMedGoogle Scholar
  13. Juniper EF: Using humanistic health outcomes data in asthma. Pharmacoecon. 2001, 19 (Suppl 2): 13-9.View ArticleGoogle Scholar
  14. National Institute for Health and Clinical Excellence: The guidelines manual (January 2009). 2011, London: National Institute for Health and Clinical Excellence, Available at http://www.nice.org.uk Google Scholar
  15. STROBE Statement (2009). 2012, Available at http://www.strobe-statement.org/index.php?id=available-checklists
  16. Vandenbroucke JP, von Elm E, Altman DG, Gøtzsche PC, Mulrow CD, Pocock SJ, Poole C, Schlesselman JJ, Egger M: STROBE initiative: strengthening the reporting of observational studies in epidemiology (STROBE): explanation and elaboration. PLoS Med. 2007, 4: e297-10.1371/journal.pmed.0040297.View ArticlePubMedPubMed CentralGoogle Scholar
  17. Statistics Canada: Consumer price index. 2012, Available at http://www.statcan.gc.ca Google Scholar
  18. Blais L, Beauchesne M-F, Forget A: Acute care among asthma patients using budesonide/formoterol or fluticasone propionate/salmeterol. Respir Med. 2009, 103: 237-43. 10.1016/j.rmed.2008.09.001.View ArticlePubMedGoogle Scholar
  19. Rosychuk R, Voaklander D, Klassen T, Senthilselvan A, Marrie TJ, Rowe BH: Asthma presentations by children to emergency departments in a Canadian province: a population-based study. Pediatr Pulmonol. 2010, 45: 985-92. 10.1002/ppul.21281.View ArticlePubMedGoogle Scholar
  20. Crighton EJ, Mamdani MM, Upshur RE: A population based time series analysis of asthma hospitalisations in Ontario, Canada: 1988 to 2000. BMC Health Serv Res. 2001, 1: 7-10.1186/1472-6963-1-7.View ArticlePubMedPubMed CentralGoogle Scholar
  21. Ungar W, Paterson J, Gomes T, Bikangaga P, Gold M, To T, Kozyrskyj AL: Relationship of asthma management, socioeconomic status, and medication insurance characteristics to exacerbation frequency in children with asthma. Ann Allergy Asthma Immunol. 2011, 106: 17-23. 10.1016/j.anai.2010.10.006.View ArticlePubMedGoogle Scholar
  22. Disano J, Goulet J, Muhajarine N, Neudorf C, Harvey J: Social-economic status and rates of hospital admission for chronic disease in urban Canada. Can Nurse. 2010, 106: 24-9.PubMedGoogle Scholar
  23. Rowe BH, Bota GW, Clark S, Camargo CA: Multicenter airway research collaboration investigators. Comparison of Canadian vs. American emergency department visits for acute asthma. Can Respir J. 2007, 14: 331-7.View ArticlePubMedPubMed CentralGoogle Scholar
  24. To T, Dell S, Dick P, Cicutto L: The burden of illness experienced by young children associated with asthma: a population-based cohort study. J Asthma. 2008, 45: 45-9. 10.1080/02770900701815743.View ArticlePubMedGoogle Scholar
  25. Lemiere C, Forget A, Dufour M, Boulet LP, Blais L: Characteristics and medical resource use of asthmatic subjects with and without work-related asthma. J Allergy Clin Immunol. 2007, 120: 1354-9. 10.1016/j.jaci.2007.07.043.View ArticlePubMedGoogle Scholar
  26. To T, Gershon A, Wang C, Dell S, Cicutto L: Persistence and remission in childhood asthma: a population-based asthma birth cohort study. Arch Pediatr Adolesc Med. 2007, 161: 1197-204. 10.1001/archpedi.161.12.1197.View ArticlePubMedGoogle Scholar
  27. Agha M, Glazier R, Guttmann A: Relationship between social inequalities and ambulatory care-sensitive hospitalisations persists for up to 9 years among children born in a major Canadian urban center. Ambul Pediatr. 2007, 7: 258-62. 10.1016/j.ambp.2007.02.005.View ArticlePubMedGoogle Scholar
  28. Lougheed M, Garvey N, Chapman K, Cicutto L, Dales R, Day AG, Hopman WM, Lam M, Sears MR, Szpiro K, To T, Paterson NA: Ontario respiratory outcomes research network: the Ontario asthma regional variation study: emergency department visit rates and the relation to hospitalization rates. Chest. 2006, 129: 909-17. 10.1378/chest.129.4.909.View ArticlePubMedGoogle Scholar
  29. Dik N, Anthonisen N, Manfreda J, Roos LL: Physician-diagnosed asthma and allergic rhinitis in Manitoba: 1985–1998. Ann Allergy Asthma Immunol. 2006, 96: 69-75. 10.1016/S1081-1206(10)61042-3.View ArticlePubMedGoogle Scholar
  30. Sin DD, Tu JV: Inhaled corticosteroid therapy reduces the risk of rehospitalisation and all-cause mortality in elderly asthmatics. Eur Respir J. 2001, 17: 380-5. 10.1183/09031936.01.17303800.View ArticlePubMedGoogle Scholar
  31. Rowe BH, Villa Roel C, Abu-Laban RB, Stenstrom R, Mackey D, Stiell IG, Campbell S, Young B: Admissions to Canadian hospitals for acute asthma: a prospective, multicenter study. Can Respir J. 2010, 17: 25-30.View ArticlePubMedPubMed CentralGoogle Scholar
  32. Sin D, Svenson L, Cowie RL, Man SF: Can universal access to healthcare eliminate health inequities between children of poor and nonpoor families?: A case study of childhood asthma in Alberta. Chest. 2003, 124: 51-6. 10.1378/chest.124.1.51.View ArticlePubMedGoogle Scholar
  33. Ungar WJ, Coyte PC: Pharmacy medication monitoring program advisory board. Prospective study of the patient-level cost of asthma care in children. Pediatr Pulmonol. 2001, 32: 101-8. 10.1002/ppul.1095.View ArticlePubMedGoogle Scholar
  34. Anis AH, Guh D, Stieb D, Leon H, Beveridge RC, Burnett RT, Dales RE: The costs of cardiorespiratory disease episodes in a study of emergency department use. Can J Public Health. 2000, 91: 103-6.PubMedGoogle Scholar
  35. Boulet L, FitzGerald J, McIvor R, Zimmerman S, Chapman KR: Influence of current or former smoking on asthma management and control. Can Respir J. 2008, 15: 275-9.View ArticlePubMedPubMed CentralGoogle Scholar
  36. Klomp H, Lawson J, Cockcroft D, Chan BT, Cascagnette P, Gander L, Jorgenson D: Examining asthma quality of care using a population-based approach. CMAJ. 2008, 178: 1013-21. 10.1503/cmaj.070426.View ArticlePubMedPubMed CentralGoogle Scholar
  37. Iron K, Manuel D, Williams J: Using a linked data set to determine the factors associated with utilization and costs of family physician services in Ontario: effects of self-reported chronic conditions. Chronic Dis Can. 2003, 24: 124-32.PubMedGoogle Scholar
  38. Anis AH, Lynd LD, Wang XH, King G, Spinelli JJ, Fitzgerald M, Bai T, Paré P: Double trouble: impact of inappropriate use of asthma medication on the use of healthcare resources. CMAJ. 2001, 164: 625-31.PubMedPubMed CentralGoogle Scholar
  39. Baibergenova A, Thabane L, Akhtar-Danesh N, Levine M, Gafni A, Moineddin R, Pulcins I: Effect of gender, age, and severity of asthma attack on patterns of emergency department visits due to asthma by month and day of the week. Eur J Epidemiol. 2005, 20: 947-56. 10.1007/s10654-005-3635-6.View ArticlePubMedGoogle Scholar
  40. Lynd LD, Sandford AJ, Kelly EM, Paré PD, Bai TR, Fitzgerald JM, Anis AH: Reconcilable differences: a cross-sectional study of the relationship between socioeconomic status and the magnitude of short-acting beta-agonist use in asthma. Chest. 2004, 126: 1161-8. 10.1378/chest.126.4.1161.View ArticlePubMedGoogle Scholar
  41. Suissa S, Ernst P, Kezouh A: Regular use of inhaled corticosteroids and the long term prevention of hospitalisation for asthma. Thorax. 2002, 57: 880-4. 10.1136/thorax.57.10.880.View ArticlePubMedPubMed CentralGoogle Scholar
  42. Seung S, Mittmann N: Urgent care costs of uncontrolled asthma in Canada, 2004. Can Respir J. 2005, 12: 435-6.View ArticlePubMedGoogle Scholar
  43. Blais L, Kettani F-Z, Lemière C, Beauchesne MF, Perreault S, Elftouh N, Ducharme FM: Inhaled corticosteroids vs. leukotriene-receptor antagonists and asthma exacerbations in children. Respir Med. 2011, 105: 846-55. 10.1016/j.rmed.2010.12.007.View ArticlePubMedGoogle Scholar
  44. Sin DD, Tu JV: Underuse of inhaled steroid therapy in elderly patients with asthma. Chest. 2001, 119: 720-5. 10.1378/chest.119.3.720.View ArticlePubMedGoogle Scholar
  45. Rowe B, Voaklander D, Wang D, Senthilselvan A, Klassen TP, Marrie TJ, Rosychuk RJ: Asthma presentations by adults to emergency departments in Alberta, Canada: a large population-based study. Chest. 2009, 135: 57-65. 10.1378/chest.07-3041.View ArticlePubMedGoogle Scholar
  46. Malo J, L’Archevêque J, Ghezzo H: Direct costs of occupational asthma in Quebec between 1988 and 2002. Can Respir J. 2008, 15: 413-6.View ArticlePubMedPubMed CentralGoogle Scholar
  47. Kohen D: Asthma and school functioning. Health Rep. 2010, 21: 35-45.PubMedGoogle Scholar
  48. Thanh NX, Ohinmaa A, Yan C: Asthma-related productivity losses in Alberta, Canada. J Asthma Allergy. 2009, 2: 43-8.View ArticlePubMedPubMed CentralGoogle Scholar
  49. Ungar WJ, Coyte PC: Measuring productivity loss days in asthma patients the pharmacy medication monitoring program and advisory board. Health Econ. 2000, 9: 37-46. 10.1002/(SICI)1099-1050(200001)9:1<37::AID-HEC483>3.0.CO;2-S.View ArticlePubMedGoogle Scholar
  50. Zimmerman B, D'Urzo A, Bérubé D: Efficacy and safety of formoterol turbuhaler® when added to inhaled corticosteroid treatment in children with asthma. Pediatr Pulmonol. 2004, 37: 122-7. 10.1002/ppul.10404.View ArticlePubMedGoogle Scholar
  51. Miedinger D, Lavoie KL, L'Archeveque J, Ghezzo H, Malo JL: Identification of clinically significant psychological distress and psychiatric morbidity by examining quality of life in subjects with occupational asthma. Health Qual Life Outcomes. 2011, 9: 76-10.1186/1477-7525-9-76.View ArticlePubMedPubMed CentralGoogle Scholar
  52. Lavoie K, Cartier A, Labrecque M, Bacon SL, Lemière C, Malo JL, Lacoste G, Barone S, Verrier P, Ditto B: Are psychiatric disorders associated with worse asthma control and quality of life in asthma patients?. Respir Med. 2005, 99: 1249-57. 10.1016/j.rmed.2005.03.003.View ArticlePubMedGoogle Scholar
  53. Bacon S, Bouchard A, Loucks E, Lavoie KL: Individual-level socioeconomic status is associated with worse asthma morbidity in patients with asthma. Respir Res. 2009, 10: 125-10.1186/1465-9921-10-125.View ArticlePubMedPubMed CentralGoogle Scholar
  54. McTaggart-Cowan HM, Marra CA, Yang Y, Brazier JE, Kopec JA, FitzGerald JM, Anis AH, Lynd LD: The validity of generic and condition-specific preference-based instruments: the ability to discriminate asthma control status. Qual Life Res. 2008, 17: 453-62. 10.1007/s11136-008-9309-6.View ArticlePubMedGoogle Scholar
  55. Rowe B, Wong E, Blitz S, Diner B, Mackey D, Ross S, Senthilselvan A: Adding long-acting beta-agonists to inhaled corticosteroids after discharge from the emergency department for acute asthma: a randomized controlled trial. Acad Emerg Med. 2007, 14: 833-40. 10.1111/j.1553-2712.2007.tb02313.x.View ArticlePubMedGoogle Scholar
  56. Yacoub MR, Lavoie K, Lacoste G, Daigle S, L'Archevêque J, Ghezzo H, Lemière C, Malo JL: Assessment of impairment/disability due to occupational asthma through a multidimensional approach. Eur Respir J. 2007, 29: 889-96. 10.1183/09031936.00127206.View ArticlePubMedGoogle Scholar
  57. Lavoie K, Bacon S, Barone S, Cartier A, Ditto B, Labrecque M: What is worse for asthma control and quality of life: depressive disorders, anxiety disorders, or both?. Chest. 2006, 130: 1039-47. 10.1378/chest.130.4.1039.View ArticlePubMedGoogle Scholar
  58. Lavoie K, Bacon S, Labrecque M, Cartier A, Ditto B: Higher BMI is associated with worse asthma control and quality of life but not asthma severity. Respir Med. 2006, 100: 648-57. 10.1016/j.rmed.2005.08.001.View ArticlePubMedGoogle Scholar
  59. Mo F, Choi B, Li F, Merrick J: Using Health Utility Index (HUI) for measuring the impact on health-related quality of life (HRQL) among individuals with chronic diseases. Sci World J. 2004, 4: 746-57.View ArticleGoogle Scholar
  60. Fitzgerald JM, Shragge D, Haddon J, Jennings B, Lee J, Bai T, Pare P, Kassen D, Grunfeld A: A randomized, controlled trial of high dose, inhaled budesonide vs. oral prednisone in patients discharged from the emergency department following an acute asthma exacerbation. Can Respir J. 2000, 7: 61-7.View ArticlePubMedGoogle Scholar
  61. Williams AE, Agier L, Wiklund I, Frith L, Gul N, Juniper E: Transcultural and measurement evaluation of the asthma quality-of-life questionnaire. Health Outcomes Research in Medicine. 2010, 1: e69-e79. 10.1016/j.ehrm.2010.09.003.View ArticleGoogle Scholar
  62. Lavoie K, Bouthillier D, Bacon S, Lemière C, Martin J, Hamid Q, Ludwig M, Olivenstein R, Ernst P: Psychologic distress and maladaptive coping styles in patients with severe vs moderate asthma. Chest. 2010, 137: 1324-31. 10.1378/chest.09-1979.View ArticlePubMedGoogle Scholar
  63. Miedinger D, Lavoie K, L’Archevêque J, Ghezzo H, Zunzunuegui MV, Malo JL: Quality-of-life, psychological, and cost outcomes 2 years after diagnosis of occupational asthma. J Occup Environmental Med. 2011, 53: 231-8. 10.1097/JOM.0b013e31820d1338.View ArticleGoogle Scholar
  64. Pre-publication history

    1. The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1471-2466/13/70/prepub

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© Ismaila et al.; licensee BioMed Central Ltd. 2013

This article is published under license to BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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