Prevalent chronic bronchitis and cough and sputum symptoms at baseline per IQR increase in each pollutant
| All participants | Cases/non-cases (n/n) | Adjusted* OR (95% CI) | ||
| PM2.5 | NO2 | Black carbon | ||
| Chronic bronchitis | 8128/124 467 | 1.01 (0.98 to 1.04) | 1.05 (1.02 to 1.08) | 1.06 (1.03 to 1.09) |
| Usual sputum | 13 687/118 704 | 1.04 (1.01 to 1.06) | 1.07 (1.04 to 1.10) | 1.07 (1.04 to 1.09) |
| Chronic cough | 9754/122 915 | 1.00 (0.97 to 1.03) | 1.03 (1.00 to 1.06) | 1.05 (1.02 to 1.08) |
| Usual cough | 19 564/112 409 | 1.03 (1.01 to 1.05) | 1.07 (1.05 to 1.09) | 1.07 (1.05 to 1.09) |
Statistically significant results are shown in bold.
*Model adjusted for sex, age, educational attainment (low: junior secondary/lower vocational or less, medium: senior secondary/secondary vocational, high: higher vocational/university), BMI (continuous), smoking status (never/ex/current), pack-years smoking and environmental tobacco smoke at home. IQR for PM2.5=1.30 µg/m3, for NO2=6.92 µg/m3 and for BC=0.29×10−5 m−1.
BC, black carbon; BMI, body mass index; NO2, nitrogen dioxide; PM2.5, particulate matter with a diameter of less than 2.5 µm.