PHYSICAL-ACTIVITY AND COLON-CANCER - A PUBLIC-HEALTH PERSPECTIVE

PURPOSE: It has been suggested that performing physical activity for a t least 30 min on most days of the week will improve health. The purpo se of this study was to assess the association between physical activi ty and colon cancer as it relates to this public health recommendation . METHODS: A large population-based case-control study of colon cancer was conducted. Study participants came from three areas of the United States: Northern California, Utah, and the Twin Cities Metropolitan A rea in Minnesota. RESULTS: Long-term involvement in high levels of act ivity, equivalent to greater than or equal to 60 min of vigorous activ ity per session, was associated with decreased risk (odds ration [OR], 0.68; 95% confidence interval [CI] 0.52-0.87). The amount of time inv olved in the activity appeared to have a greater impact than the numbe r of days per week that activities were performed. Those reporting the highest level of activity, as defined by both duration and vigorous i ntensity, were at the lowest risk (OR, 0.62; 95% CI, 0.52-0.75) relati ve to those who were sedentary; associations did not differ by age at diagnosis, site of the tumor within the colon, or sex. The inverse ass ociation between colon cancer and long-term vigorous leisure-time acti vity was slightly stronger among those without a family history of col orectal cancer than among those with a family history of colorectal ca ncer. From these data we estimate chat 13% of colon cancer could be at tributed to lack of vigorous leisure-time activity in the population; we estimate that 4.3 cases of colon cancer/100,000 population are prev ented each year because people are involved in Vigorous leisure time p hysical activity. CONCLUSIONS: Data from this study suggest that a hig h level of vigorous leisure-time activity performed over the past 20 y ears was important in reducing colon cancer risk; the greatest inverse association was observed when activities were performed for longer pe riods of time per session for the past 20 years. These and other data indicate that it is important to identify ways to facilitate an increa se in leisure-time physical activity within the population. (C) 1997 b y Elsevier Science Inc.