Table 3

Demographic information on the population of phase 2 and phase 3, with prevalence of symptoms and percentage of predicted lung function variables

Phase 2 Phase 3
Factories (n)1916
Total population (n)29552394
Participants (n)26462281
Workers included in analyses (n)23241994
Age, mean (range)(y)41  (19–64)41  (18–64)
Current smokers (%)4845
Ex-smokers (%)2729
Duration of employment (months)174.5177.9
Current inhalable dust exposure (mg.m−3)0.770.57
Cumulative inhalable dust exposure (mg.month.m−3)263.2245.9
Prevalence of cough (%)14.213.3
Prevalence of sputum (%)14.211.6
Prevalence of cough and sputum (%)8.37.4
Prevalence of chronic bronchitis (%)4.13.7
Workers with valid spirometry traces (n (%))2235 (96.0)1882 (94.4)
Predicted FEV1 (SD) (%)104.4 (14.5)104.1 (13.9)
Predicted FVC (SD) (%)110.4 (13.6)109.9 (13.2)
Predicted FEF25%–75% (SD) (%)93.4 (30.3)92.3 (28.7)
Predicted FEV1/FVC ratio (SD) (%)90.7 (8.8)90.8 (8.1)