title: Incidence of chronic bronchitis: a prospective study in a large general population.
abstract: METHODS
  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.
  
  
  METHODS
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: <label>*</label>Department of Occupational and Environmental Medicine, Sahlgrenska University Hospital, Göteborg, Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Holm
authors.affiliation: <label>*</label>Department of Occupational and Environmental Medicine, Sahlgrenska University Hospital, Göteborg, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Torén
authors.affiliation: <label>*</label>Department of Occupational and Environmental Medicine, Sahlgrenska University Hospital, Göteborg, Sweden.
authors.forename: E
authors.initials: E
authors.lastname: Andersson
mesh_terms: D000328:Adult; D017668:Age of Onset; D001249:Asthma / Q000150:complications* / Q000453:epidemiology; D029481:Bronchitis, Chronic / Q000453:epidemiology* / Q000209:etiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology; D011795:Surveys and Questionnaires; D013548:Sweden / Q000453:epidemiology