© 2007 American Thoracic Society
Does Regular Physical Activity Reduce Lung Function Decline and COPD Risk among Smokers?To the Editor:I read with interest the recent article by Garcia-Aymerich and colleagues wherein the authors have tried to demonstrate that moderate to high levels of regular physical activity are associated with reduced lung function decline and risk of chronic obstructive pulmonary disease (COPD) among smokers (1). This study does not take into consideration the very fact that there is intersubject variability in the inflammatory response in COPD since only 10 to 20% of heavy smokers develop symptomatic airflow obstruction (2). The inappropriate inflammatory response that occurs in cigarette smokers who develop COPD compared with smokers without COPD can be explained by genetic polymorphisms (3). Even among patients with severe COPD, there may be varying levels of disability despite similar levels of lung function. Polymorphisms in several genes appear to be associated with COPD-related traits other than forced expiratory volume in 1 second (3). Considering the smoking-induced inflammatory nature of COPD pathogenesis, the authors put forward the hypothesis that higher levels of regular physical activity could reduce the risk of COPD by modifying smoking-related lung function decline (1). It is logical to expect that, if COPD is purely an inflammatory condition, corticosteroids should be beneficial, but the response to corticosteroids in COPD has been disappointing (4). Besides inflammation, continued proteolytic activity results in parenchymal destruction and obliterative bronchiolitis and fibrosis. If strenuous physical activity is protective against the development of COPD, with a 21% reduction in the occurrence of new COPD cases in the present study, then why is COPD rampant in the hills of the Himalayas (5) and in manual workers (6). The present study does not take into consideration the confounding effects of diet and of statins on the rate of decline of lung function (7). Even in this study, the lack of an association between physical activity and lung function decline or COPD risk in the group of former smokers brings into question the authors' hypothesis that the antiinflammatory action of physical activity prevents the onset of COPD in the smokers. Their valuable findings should not be taken as supportive for cigarette abuse, but as overall health promotion through regular moderate to high levels of physical activity.
Christian Medical College and Hospital Ludhiana, Ludhiana, India FOOTNOTES Conflict of Interest Statement: A.S. has no financial relationship with a commercial entity that has an interest in the subject of this manuscript. REFERENCES
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