Physical activity and the risk of pneumonia in male smokers administered vitamin E and beta-carotene.

It has been proposed that moderate exercise may enhance the immune system. We evaluated whether physical activity at work or at leisure is associated with the risk of pneumonia, and whether the antioxidants vitamin E and beta-carotene affect pneumonia risk in physically active people. A cohort of 16 804 male smokers aged 50-69 years and working at study entry was drawn from the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) Study, which examined the effect of vitamin E, 50 mg/day, and beta-carotene, 20 mg/day, on lung and other cancers. Physical activity at work, and the type of leisure-time exercise, were recorded at study entry. We retrieved the first occurrence of hospital-treated pneumonia during a 3-year follow-up from the National Hospital Discharge Register (133 cases). Physical activity at work and at leisure had no association with the risk of pneumonia. In participants with physically loading jobs, neither vitamin E nor beta-carotene affected the risk of pneumonia. In participants carrying out moderate or heavy exercise at leisure, beta-carotene had no effect, but vitamin E reduced the risk of pneumonia by 50% (95% CI: 16-70%). Previously, exercise has been shown to affect diverse laboratory measures of the immune system which are, however, only surrogate markers for the resistance to infections. The lack of association between physical activity and the risk of pneumonia observed in our study emphasizes the problem of drawing conclusions from surrogate end points. The finding that vitamin E reduced the risk of pneumonia in persons carrying out leisure-time exercise warrants further study.