Setting: A county in western Sweden.
Objective: To prospectively investigate the incidence rate of chronic bronchitis (CB) in relation to smoking, age, sex, atopy and asthma in a large sample of the general population.
Design: Subjects from a county in western Sweden born between 1943 and 1973, who had participated in our previous study in 1993, were mailed a new questionnaire in 2003. Altogether 11 463 (72%) answered the questionnaire, which comprised items about smoking, atopy, respiratory symptoms and age at onset of CB symptoms. CB was defined as chronic productive cough for at least 3 months per year for 2 consecutive years.
Results: There were 98 new cases of CB during 1993-2003 in the study population aged 30-60 years at follow-up. The incidence rate was 0.9/1000 person-years (py); there was no significant difference between women and men or different age groups. However, CB incidence was higher in women in relation to smoking (incidence rate ratio 3.6, 95%CI 1.9-7.3) and in those with ever asthma (hazard ratio 5.6, 95%CI 3.5-9.0).
Conclusion: This prospective general population-based study shows an incidence rate of CB of 0.9/1000 py. Smoking and asthma were both associated with an increased risk of CB.