Exercise Cuts Breast Cancer Risk

Best results seen among women who were consistently active

By Jim Kling
WebMD Medical News Reviewed By Brunilda Nazario, MD

In case you needed one more reason to set out for that brisk morning walk or daily run, here it is: New research shows that exercise reduces a woman's risk of breast cancer. And the earlier in life you start, the better.

In a study in the February issue of Medicine & Science in Sports & Exercise, women who reported high levels of physical activity from as young as age 16 in some cases cut their risk of developing breast cancer after menopause in half, compared to women who reported no strenuous activity.

The researchers interviewed 1,550 postmenopausal and premenopausal women aged 40-85, both with and without breast cancer. The women were asked if they participated in a sport or physical activity vigorous enough to break a sweat, and how many times a week they engaged in those activities. They were then asked to give the same information for the time periods two, 10, and 20 years before the interview, and for when they were 16.

The earlier in life they exercised, the greater reduction in cancer risk the women experienced. "In a worst-case scenario for any one of those periods, there was at least about a 10-12% reduction, and it's as high as close to 50% if you look 20 years ago," researcher Joan M. Dorn, PhD, an assistant professor of social and preventive medicine at the University of Buffalo, tells WebMD.

The study joins a growing body of scientific evidence on the benefits of exercise. Other studies have linked regular exercise to improving and preventing diabetes, cardiovascular disease, colon cancer, and other chronic diseases, but this study shows that exercise early in life can affect later breast health.

The study has a drawback, though, that all such studies face, which is what's called a "healthy patient bias." In this case, women who exercise often might be more apt to take care of themselves in other ways, so that a decrease in breast cancer later in life may not be due to the exercise itself, but rather some other associated factor. The researchers accounted for this by factoring in subjects such as smoking history and weight. "After adjusting for all these factors we're pretty confident that what we see is the effect of exercise," says Dorn.

"I think this is an excellent study, and it adds to an already important body of literature that shows that patients who exercise tend to be thinner... when you have a lot of fat, the steroids normally in the body get turned into estrogens, and the longer a woman's breasts are exposed to estrogen, the higher her risk of developing breast cancer," Jay Brooks, MD, chief of hematology/oncology at the Ochsner Clinic and Hospital in New Orleans, tells WebMD.

Exercise that breaks a sweat is subjective. It might mean going for a jog for a 30-year old. For a 70-year old it might be a brisk walk. But whatever activity level it means, it gives women a tool to combat a disease that will strike one in eight women in their lifetimes. "There aren't a lot of behavioral things that women can do to reduce their risk. This is just one more piece of the puzzle saying we need to get out and move," says Dorn.

SOURCES: Joan M. Dorn, PhD, assistant professor of social and preventive medicine at the University of Buffalo Jay Brooks, MD, chief of hematology/oncology at the Ochsner Clinic and Hospital, New Orleans, La.

Source http://www.caaws.ca/e/health/article.cfm?id=106