Physical activity in leisure-time and risk of cancer:: 14-year follow-up of 28,000 Danish men and women

Aim: The preventive effect of physical activity on risk of cancer in general remains controversial. This study aimed at assessment of the associations between leisure-time physical activity and incidence of cancer in the general population of adult men and women. Methods: 13,216 women and 18,718 men aged 20 - 93 years selected from the general population participated in a health examination including a questionnaire with information on physical activity, smoking, alcohol intake, postmenopausal hormones, and socioeconomic status. Incident cases of cancers where recorded during a follow-up period of 14 years. The six most frequent cancer cases in both sexes were included in this analysis. Results: A highly significant inverse association was seen between vigorous physical activity in leisure time and cancer of the ovary, adjusted rate ratio being 0.33 (95% CI 0.16-0.67; p=0.001) for the most physical active women. In men there was a highly significant increase for non-melanoma skin cancer, with adjusted rate ratio of 1.72 (95% CI 1.23-2.40; p=0.001), for the most active men and vigorous activity was associated with a non-significant lower risk of colon cancer, the adjusted rate ratio being 0.72 (95% CI 0.47 - 1.11; p=0.06). Conclusion: Generally, there were no, or only weakly, inverse associations between physical activity in leisure time and incidence of cancer, except for cancer of the ovary.