Adjusted odds ratios (OR), 95% confidence intervals (95% CI) and p-values for the effect of smoking habits, respiratory infection before the age of 5 yrs, occupational exposure and socioeconomic status on chronic bronchitis
| 〈Males〉 | 〈Females〉 | |||
| OR | 95% CI | OR | 95% CI | |
| Smoking habits# | ||||
| Past smoker | 1.38 | 0.84–2.26 | 1.08 | 0.67–1.72 |
| Current smoker (1–14 pack-yrs) | 3.51*** | 2.31–5.32 | 3.06*** | 2.13–44.0 |
| Current smoker (15–29 pack-yrs) | 6.32*** | 4.20–9.52 | 5.02*** | 3.36–7.48 |
| Current smoker (30–44 pack-yrs) | 12.13*** | 7.57–19.46 | 8.47*** | 4.89–14.65 |
| Current smoker (≥45 pack-yrs) | 17.32*** | 9.97–30.11 | 10.63*** | 4.69–24.13 |
| Respiratory infection before the age of 5 yrs | ||||
| Yes versus no | 0.90 | 0.57–1.41 | 1.40 | 0.95–2.07 |
| Occupational exposure | ||||
| Yes versos no | 1.49* | 1.12–1.98 | 1.66*** | 1.26–2.18 |
| Socioeconomic status | ||||
| Low versus high | 1.35* | 1.01–1.81 | 1.08 | 0.79–1.48 |
#: versus nonsmokers
The ORs were calculated by a multilevel logistic regression model with random intercept at the level of the European Community Respiratory Health Survey (ECRHS) centre and all predictor variables as fixed effects. The ORs were also adjusted for the effect of the percentage of responders to questions on asthma and bronchitis in each ECRHS centre
*: p<0.05
***: p<0.001
p-values for the main factors were determined using the wald test