title: Twenty-five year trends in prevalence of chronic bronchitis and the trends in relation to smoking.
abstract: BACKGROUND
  The present study examines how the trends in the prevalence of chronic bronchitis during the last three decades associate with changes in smoking habits during the same period.
  
  
  METHODS
  Altogether 47 896 subjects aged 25-74 years were examined in six independent cross-sectional population surveys repeated every five years between 1982 and 2007 in Finland. The presence of chronic bronchitis, smoking habits and other risk factors were measured by standard questionnaires.
  
  
  RESULTS
  During the study, the prevalence of chronic bronchitis was significantly higher in men than in women. In men aged 25-64 years, the prevalence of chronic bronchitis decreased from 19% in 1982 to 13% in 2007 (p for trend <0.001). The corresponding decrease in women aged 25-64 years was from 13% to 11% (p for trend 0.009). In men aged 65-74 years, the prevalence of chronic bronchitis decreased from 24% to 19% (p for trend 0.032). Simultaneously, male smoking decreased and smoking in middle-aged women increased. However, adjusting for the changes in smoking habits did not change the declining trends in the prevalence of chronic bronchitis. The significant declining trend in chronic bronchitis was seen separately in male current smokers and in male and female never smokers aged 45-74 years and the declining trend was the greatest in male current smokers. In general, female smokers with chronic bronchitis had smoked less than their male counterparts.
  
  
  CONCLUSIONS
  There was a declining trend in the prevalence of chronic bronchitis which was probably explained by both a decrease in smoking and by other factors.
authors.affiliation: Department of Pulmonary Diseases, Kuopio University Hospital, Kuopio, Finland. Electronic address: Margit.Pelkonen@kuh.fi.
authors.forename: Margit K
authors.initials: MK
authors.lastname: Pelkonen
authors.affiliation: Finnish Information Centre for Register Research, Helsinki, Finland.
authors.forename: Irma-Leena K
authors.initials: IL
authors.lastname: Notkola
authors.affiliation: Institute for Health and Welfare, Helsinki, Finland; Institute for Public Health and Clinical Nutrition, University of Eastern Finland, Kuopio, Finland.
authors.forename: Tiina K
authors.initials: TK
authors.lastname: Laatikainen
authors.affiliation: Department of Pulmonary Diseases, Kuopio University Hospital, Kuopio, Finland.
authors.forename: Heikki O
authors.initials: HO
authors.lastname: Koskela
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D029481:Bronchitis, Chronic / Q000453:epidemiology* / Q000209:etiology; D003430:Cross-Sectional Studies; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012307:Risk Factors; D017678:Sex Distribution; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology* / Q000639:trends
keywords: Chronic bronchitis; Prevalence; Smoking; Trends