NEW YORK, July 03 (Reuters) -- An active lifestyle does as much good for women as it does for men when it comes to reducing risk of colon cancer, according to a new study.
Previous work had related risk of colon cancer to lack of exercise in men, but studies of women had been inconclusive, wrote Dr. Maria Elena Martinez, of the Harvard School of Public Health, Boston, and her associates in the Journal of the National Cancer Institute.
Moderate exercise, such as a daily hour-long walk, can reduce the risk of developing colon cancer by 46%, the investigators said.
They gathered data from the Nurses' Health Study, a research program begun in 1976, in which more than 120,000 female registered nurses completed personal health questionnaires every two years.
The women listed the amount of time spent per week at a variety of leisure-time activities, including walking, jogging, bicycling, swimming, racquet sports, aerobics, rowing, and calisthenics. Researchers then calculated the energy expended in each activity.
The active women in this study also had other good health habits. They tended to consume less dietary fat, including less animal fat, and more fiber than less-active women. Physically active women also were leaner, less likely to smoke, and more likely to take vitamins and postmenopausal hormones.
When the statistical analysis was controlled to account for these effects, however, exercise still had an independent association with decreased colon cancer risk, the investigators reported.
They also looked at women's body mass index, or weight divided by height, which is a more accurate measure of body fat than weight alone. A body mass index of less than 25 is considered acceptable, and obesity is defined as a body mass index of 30 or more.
Women with the highest body mass indexes, greater than 29, were at almost twice the risk of developing colon cancer compared with women in the lowest category, with a body mass index of less than 21.
Surveys show that nearly one-fourth of the U.S. population gets no exercise at all. Another 54% is somewhat more active but still falls short of current recommendations for at least 30 minutes per day of light to moderate physical activity.
SOURCE: Journal of the National Cancer Institute (1997;89:948-955)
