Background and purpose: It has been proposed that moderate regular aerobic training may enhance immunocompetence, whereas excessive training may cause immunosuppression. We evaluated whether physical activity at work, or at leisure, is associated with the risk of the common cold, and whether the antioxidants vitamin E and beta-carotene affect common cold risk in physically active people.
Methods: A cohort of 14,401 men aged 50-69 yr 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.d(-1), and beta-carotene, 20 mg.d(-1), on lung cancer in smokers using a 2 x 2 factorial design. The trial was conducted in southwestern Finland in 1985-1993; the intervention lasted for 6.1 yr (median). Physical activity at work, and the type and frequency of leisure-time exercise were recorded at study entry. The subjects were questioned about common cold episodes 3x yr-1. We modeled the cumulative incidence of colds during a 2-yr follow-up period with Poisson regression, adjusting for potential confounders.
Results: Physical activity at work and at leisure had no association with common cold risk. In subjects with physically load-bearing jobs, neither vitamin E nor beta-carotene affected significantly the risk of common cold. In subjects carrying out heavy exercise at leisure, vitamin E and beta-carotene increased the risk of colds when compared with placebo.
Conclusions: Contrary to previous suggestions, moderate physical activity is not associated with lower risk of common cold in middle-aged male smokers. It has been previously proposed that antioxidant supplementation might be beneficial for subjects carrying out heavy exercise, but in our study vitamin E and beta-carotene increased the risk of colds in subjects carrying out heavy exercise at leisure.