Subgroup analyses for prevalent chronic bronchitis and cough and sputum symptoms at baseline, per IQR increase in each pollutant
| Cases/non-cases (n/n) | Adjusted* OR (95% CI) | |||
| PM2.5 | NO2 | Black carbon | ||
| Females | ||||
| Chronic bronchitis | 4070/73 210 | 1.03 (0.99 to 1.08) | 1.08 (1.03 to 1.13) | 1.08 (1.04 to 1.13) |
| Usual sputum | 7268/69 987 | 1.05 (1.02 to 1.08) | 1.08 (1.04 to 1.12) | 1.08 (1.05 to 1.11) |
| Chronic cough | 5384/71 924 | 1.03 (0.99 to 1.07) | 1.07 (1.03 to 1.11) | 1.08 (1.04 to 1.11) |
| Usual cough | 11 194/65 731 | 1.04 (1.02 to 1.07) | 1.09 (1.06 to 1.12) | 1.09 (1.06 to 1.12) |
| Age >=50 | ||||
| Chronic bronchitis | 2669/37 639 | 0.98 (0.94 to 1.03) | 0.99 (0.94 to 1.05) | 1.03 (0.98 to 1.09) |
| Usual sputum | 4104/36 162 | 1.01 (0.98 to 1.06) | 1.01 (0.97 to 1.06) | 1.03 (0.99 to 1.08) |
| Chronic cough | 2999/37 333 | 0.99 (0.94 to 1.03) | 1.02 (0.97 to 1.08) | 1.06 (1.01 to 1.11) |
| Usual cough | 5457/36 606 | 1.01 (0.97 to 1.04) | 1.05 (1.01 to 1.09) | 1.06 (1.02 to 1.10) |
| No post-secondary education | ||||
| Chronic bronchitis | 6120/85 542 | 1.00 (0.96 to 1.03) | 1.06 (1.02 to 1.10) | 1.07 (1.03 to 1.11) |
| Usual sputum | 10 293/81 340 | 1.02 (0.99 to 1.05) | 1.07 (1.04 to 1.10) | 1.08 (1.05 to 1.11) |
| Chronic cough | 7427/84 296 | 1.00 (0.97 to 1.03) | 1.04 (1.00 to 1.08) | 1.06 (1.03 to 1.10) |
| Usual cough | 14 625/76 626 | 1.03 (1.01 to 1.06) | 1.08 (1.05 to 1.11) | 1.08 (1.06 to 1.11) |
| Never smokers | ||||
| Chronic bronchitis | 2960/59 935 | 1.03 (0.98 to 1.08) | 1.09 (1.03 to 1.14) | 1.07 (1.02 to 1.12) |
| Usual sputum | 5426/57 441 | 1.05 (1.02 to 1.09) | 1.10 (1.06 to 1.14) | 1.08 (1.05 to 1.12) |
| Chronic cough | 3472/59 456 | 1.04 (1.00 to 1.09) | 1.05 (1.01 to 1.11) | 1.06 (1.02 to 1.11) |
| Usual cough | 8115/54 585 | 1.07 (1.04 to 1.10) | 1.09 (1.06 to 1.13) | 1.08 (1.05 to 1.11) |
| Asthmatics | ||||
| Chronic bronchitis | 1781/9831 | 0.99 (0.92 to 1.05) | 1.03 (0.96 to 1.11) | 1.04 (0.97 to 1.11) |
| Usual sputum | 2820/8802 | 1.10 (1.04 to 1.16) | 1.12 (1.06 to 1.19) | 1.12 (1.07 to 1.19) |
| Chronic cough | 2039/9589 | 1.04 (0.97 to 1.10) | 1.05 (0.98 to 1.12) | 1.07 (1.01 to 1.14) |
| Usual cough | 3362/8209 | 1.06 (1.00 to 1.11) | 1.08 (1.02 to 1.14) | 1.10 (1.04 to 1.15) |
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 x 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.