Physical activity and the risk of community-acquired pneumonia in US women.

BACKGROUND

Exercise bolsters the immune system and can prevent various infections in certain populations. However, limited data exist regarding the role of physical activity and the risk of community-acquired pneumonia.

METHODS

During a 12-year period, we prospectively examined the association between physical activity and the risk of community-acquired pneumonia among 83,165 women in the Nurses' Health Study II who were between the ages of 27 and 44 years in 1991. We excluded women who had pneumonia before 1991 and those with a history of cancer, cardiovascular disease, or asthma. Biennial self-administered mailed questionnaires were used to determine activity level. Cases of pneumonia required a diagnosis by a physician and confirmation with a chest radiograph.

RESULTS

We identified 1265 new cases of community-acquired pneumonia during 965,168 person-years of follow up. After adjusting for age, women in the highest quintile of physical activity were less likely to develop pneumonia than women in the lowest quintile (relative risk [RR] = 0.72; 95% confidence interval [CI], 0.60-0.86; P for trend<.001). However, the association was attenuated and only marginally significant after further adjusting for body mass index, smoking, and alcohol use (RR=0.84; 95% CI, 0.70-1.01; P for trend=.06). Women in the highest quintile of walking were less likely to develop pneumonia compared with women who walked the least (multivariate adjusted RR=0.82; 95% CI, 0.69-0.98); however, the trend across quintiles was not significant (P for trend=.25).

CONCLUSION

Higher physical activity does not substantially reduce pneumonia risk in well-nourished women.