Background: Overall, lifelong smokers die about 10 years earlier than comparable non-smokers, and at least one fourth of the excess mortality is caused by chronic obstructive pulmonary disease (COPD) and lung cancer. About 10 to 15 percent of smokers develop COPD, but the optimal strategy to identify those most at risk is unknown. Geijer and colleagues conducted a prospective cohort study of men living in a small Dutch town to better understand the rate of progression to COPD and the factors that influence this change in smokers.
The Study: In 1998, baseline spirometry was performed on 702 male smokers 40 to 65 years of age who had no known lung disease. Participants also completed the Airways Questionnaire, a short questionnaire on health-related quality of life and the impact of respiratory symptoms such as cough and dyspnea. The average age at enrollment was 50 years. Participants had smoked an average of 30 years and had an individual average of 24 pack-years. The predicted forced vital capacity and forced expiratory volume in one second were 111 and 102 percent, respectively.
Results: During the mean follow-up period of 5.2 years, the cumulative incidence of moderate COPD was 8.3 percent, equivalent to 1.6 percent per year. No participant developed severe or very severe COPD during the study. The strongest predictor of COPD was abnormal spirometry at baseline. One out of five participants who had mild COPD on entry to the study progressed to moderate COPD compared with one out of 25 smokers with normal spirometry at baseline. Developing moderate COPD was also significantly associated with age older than 55 years, heavier smoking, onset of smoking before 15 years of age, consultation for lower respiratory tract infection, and self-reported cough. A family history of COPD was not significantly associated with development of COPD in smokers. In multivariate analysis, age, early initiation of smoking, and symptoms (cough and consultations for lower respiratory tract conditions) were independently associated with development of moderate COPD.
Conclusion: The authors conclude that in a primary care practice, about 8 percent of middle-age male smokers progress to moderate COPD over five years. Those most at risk are older, began smoking at an early age, and have contacts with their physician because of cough and other respiratory problems. Smoking cessation can normalize lung function and decrease morbidity and mortality, even in smokers with early COPD.