Exercise Slows Lung Function Decline in Smokers

March 1, 2007

BARCELONA Spain -- Smokers who get plenty of exercise regularly may slow the inevitable decline of their lung function and reduce their risk of chronic obstructive pulmonary disease, researchers here reported.

BARCELONA, Spain, March 1 -- Smokers who get plenty of exercise regularly may slow the inevitable decline of their lung function and reduce their risk of chronic obstructive pulmonary disease, researchers here reported.

Compared with indolent smokers, the physically active who reported moderate to high levels of exercise had a slower decline in FEV1 and FEV and a more than 20% reduced risk of developing COPD, according to a report in the March issue of the American Journal of Respiratory and Critical Care Medicine.

Moderate to high levels of physical activity among smokers avoided 21% of the potentially new COPD cases, said Judith Garcia-Aymerich, M.D., of the Institut Municipal d'Investigaci Mdica here, and colleagues here and in Denmark.

These findings emerged from a population-based sample of 6,790 smokers and non-smokers (43% men, mean age 52) recruited from the Copenhagen City Heart Study over 10 years, starting in 1981 to 1983, and followed through 1991-1994.

Of the participants, 23%, 22%, and 55% were never-, former-, and active smokers, respectively. Mean level of physical activity between baseline and follow-up was classified as low (15.6%), moderate (50%), and high (38%), according to a questionnaire.

Smoking status during the 10-year study did not change for 86% of the participants, although 10% quit, 2% started, and 2% resumed smoking.

COPD was defined as FEV1/FVC ? 70%. Adjusted associations between physical activity and FEV1 and FVC decline, and COPD incidence, were obtained using linear and logistic regression, respectively.

Active smokers with moderate and high physical activity had a reduced FEV1and FVC decline compared with largely sedentary smokers. These findings held only for active smokers, the researchers noted.

After adjusting for all potential confounders and risk factors, the relative change was +2.6 and +4.8 mL/yr of FEV1, P-for-trend = 0.006, and +2.6, and +7.7 mL/yr of FVC, P-for-trend

Potential study limitations, the authors said, are a possible misclassification of exposure, survival bias, and residual confounding factors, while the use of a questionnaire involved some degree of misclassification.

The authors also pointed out that the study design cannot determine causality. "Reverse causation is also possible even in a longitudinal study," they wrote. "Repeated measures of lung function and physical activity would be needed to discard it. Unfortunately these data are not available in the present study."

Also, the results were adjusted for various risk factors, with the exception of diet for which, unfortunately, information was not available.

The increase in smoking and sedentary lifestyle in developing countries is likely to have an important impact with respect to COPD, which already has a leading position both for mortality and disability throughout the world, Dr. Garcia-Aymerich said.

Beyond the importance of reinforcing antismoking initiatives, the recommendation of increasing the level of physical activity may be especially important in active smokers, as supported by the findings of this study, the researchers concluded.