Impact of air pollution on respiratory diseases in children with recurrent wheezing or asthma

BMC Pulmonary Medicine

Table 4 Multivariate rate ratios (RR) and 95% confidence intervals (CI) of pneumonia events in children with recurrent wheezing or asthma and healthy children according to air pollutant levels

	Asthmatic subjects (329 subjects; =143 events)	Healthy subjects (364 subjects; n = 80 events)
	RR (95% CI)^a	RR (95% CI)^a
PM ₁₀ (lag 0–2 days) ^b
Low (<30 μg/m³)	1 (reference)	1 (reference)
Intermediate (30- < 50 μg/m³)	1.23 (0.73-2.05)	1.47 (0.76-2.84)
High (≥50 μg/m³)	1.62 (0.92-2.87)	1.04 (0.46-2.33)
Continuous RR ^d	1.08 (1.00-1.17)	0.99 (0.88-1.11)
NO ₂ (lag 0–2 days) ^c
Lowest tertile (<89 μg/m³)	1 (reference)	1 (reference)
Intermediate tertile (89- < 113 μg/m³)	1.20 (0.75-1.90)	1.45 (0.80-0.63)
Highest tertile (≥113 μg/m³)	1.56 (1.01-2.42)	1.24 (0.67-2.31)
Continuous RR ^d	1.08 (1.01-1.17)	1.02 (0.93-1.12)

^aRRs and 95% CIs were obtained from multivariate repeated-measures analyses adjusted for age, sex, education of parents, presence of smokers at home, season, day of week, temperature and relative humidity; ^bthe mean of three days (day -2 to day 0) for the daily weighted average PM₁₀ in the municipality of residence of each subject; ^cthe mean of three days (day -2 to day 0) of the maximum daily level of NO₂ in the municipality of residence of each subject. ^dthe results represent the increase (or decrease) in risk corresponding to an increment of 10 μg/m³ in the level of the pollutant examined.

ISSN: 1471-2466