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* From the Departments of Public Health and General Practice (Dr. Pelkonen) and Pulmonary Diseases (Drs. Tukiainen and Koskela) Kuopio University Hospital, Kuopio; and Department of Epidemiology and Health Promotion (Drs. Notkola and Nissinen), National Public Health Institute, Helsinki, Finland.
Correspondence to: Margit Pelkonen, MD, University of Kuopio, Department of Public Health and General Practice, PO Box 1627, FIN-70211 Kuopio, Finland; e-mail: Margit.Pelkonen{at}uku.fi
Abstract
Purpose: To describe the 30-year cumulative incidence of chronic bronchitis and COPD in relation to smoking habits. The effect of chronic bronchitis on pulmonary function and mortality was also examined.
Methods: Middle-aged men belonging to two rural Finnish cohorts of the Seven Countries Study (n = 1,711 in 1959) were followed up for up to 40 years until 2000. Standard questionnaires were used to measure chronic bronchitis, and repeated spirometry was used to evaluate pulmonary function during the 30 years. Forty-year mortality data were examined.
Results: The cumulative incidence of chronic bronchitis and COPD was 42% and 32%, respectively, in continuous smokers, compared to 26% and 14% in ex-smokers and 22% and 12% in never-smokers. During the follow-up, subjects with chronic bronchitis had on average 252 mL (95% confidence interval, 211 to 293 mL) lower forced expiratory volume than those without it. The decrease in forced expiratory volume attributable to chronic bronchitis was most pronounced in those with persistent symptoms and in smokers. In subjects with chronic bronchitis, all-cause mortality was increased by a hazard ratio of 1.30 (95% confidence interval, 1.02 to 1.65). Smokers with chronic bronchitis who decreased their daily cigarette consumption increased their median life span by 2.4 years.
Conclusions: The lifetime risk of chronic bronchitis among smokers is approximately two in five, and almost one half of smokers who have chronic bronchitis also acquire COPD. Chronic bronchitis is related to earlier death, also in never-smokers, probably partly through a rapid decline in pulmonary function.
Key Words: chronic bronchitis COPD mortality pulmonary function smoking
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