Effects of toner-handling work on respiratory function, chest X-ray findings, and biomarkers of inflammation, allergy, and oxidative stress: a 10-year prospective Japanese cohort study

Table 4 Analysis of the health effects of toner exposure without adjustment for confounders (models 1 and 2)

Parameters (unit)	Difference in yearly change in each parameter between the toner-handling group and non-toner-handling group (model 1)					Difference in yearly change in each parameter between the toner-handling group and non-toner-handling group (model 2)
Parameters (unit)	Estimate	95% CI		P-value	AIC	Estimate	95% CI		P-value	AIC
Respiratory function tests
VC (l)	0.0009	−0.002	0.003	0.459	− 3786.6	− 0.003	− 0.005	0.0002	0.067	− 4375.4
%VC (%)	0.004	− 0.05	0.06	0.892	74,963.3	−0.07	− 0.1	− 0.004	0.037	74,441.0
FEV₁ (l)	0.0001	−0.002	0.002	0.925	− 7999.7	−0.001	− 0.004	0.001	0.272	− 8462.7
%FEV₁ (%)	0.02	− 0.05	0.08	0.608	76,776.5	−0.02	− 0.09	0.05	0.568	76,306.5
FEV₁/FVC (%)	−0.003	− 0.04	0.03	0.866	60,893.8	−0.002	− 0.04	0.04	0.903	60,721.0
%FEV₁/FVC (%)	0.006	−0.04	0.05	0.808	65,957.3	0.008	−0.04	0.06	0.727	65,790.5
V25 (l/s)	0.0005	−0.003	0.004	0.747	4573.4	0.0002	−0.004	0.004	0.921	4303.0
%V25 (%)	−0.06	− 0.2	0.10	0.457	102,127.6	−0.02	− 0.20	0.15	0.784	101,834.2
Biomarkers
CRP (mg/dl)	0.0007	−0.002	0.003	0.635	3626.3	0.0006	−0.002	0.003	0.658	3620.2
IgE (IU/ml)	3.2	−1.6	7.9	0.190	177,623.3	4.6	−1.00	10.1	0.108	175,403.0
8-OHdG/Creatinine (ng/mg)	−0.01	− 0.03	0.0009	0.065	45,402.9	−0.01	−0.03	0.003	0.115	45,352.5

Dependent variables comprised the parameters of respiratory function tests and the values of biomarkers in both models 1 and 2. In model 1, we treated toner-handling work, the survey year, and the interaction between toner-handling work and survey year as fixed effects and treated only the individual differences at baseline as the random effect (random intercept model). In model 2, we treated certain individual differences during the observation period and the individual differences at baseline as random effects (random intercept and slope models)
CI confidence interval, AIC Akaike’s Information Criterion, VC vital capacity, %VC percentage of VC to predicted VC value, FEV₁ forced expiratory volume in 1 s, %FEV₁ percentage of FEV₁ to predicted FEV₁ value, FEV₁/FVC percentage of forced expiratory volume in 1 s, %FEV₁/FVC percentage of FEV₁/FVC to predicted FEV₁/FVC value, V25 maximal expiratory flow at 25% forced VC, CRP C-reactive protein, IgE immunoglobulin E, 8-OHdG 8-hydroxy-2′-deoxyguanosine

ISSN: 1471-2466