Regular exercise for young women can reduce their risk of breast cancer

The latest research on breast cancer is good news, it says that regular exercise can reduce the risk.

In a large and detailed analysis on the effects of exercise on premenopausal breast cancer, researchers have found that girls and young women who exercise regularly between the ages of 12 and 35 have a substantially lower risk of breast cancer before menopause.

The study of nearly 65,000 women by researchers in the U.S. found that young women who were physically active, particularly between ages 12 to 22, had a 23 percent lower risk of breast cancer before menopause.

The researchers from Washington University School of Medicine and Harvard University say it is clear that physical activity during adolescence and young adulthood can reduce a woman's risk of early breast cancer.

Lead researcher Professor Graham Colditz, from Washington University, says this is just one more reason to encourage young girls and women to exercise regularly.

A quarter of all breast cancers are diagnosed in women before menopause and these can be more aggressive and harder to treat than breast cancer in older women.

There is ample research which shows that physical activity reduces the risk of postmenopausal breast cancer, however research examining whether exercise can influence the breast cancer risk before menopause, is scant and often conflicting.

The study used data on almost 65,000 women enrolled in the Nurses' Health Study II, where after six years of follow-up, 550 women were diagnosed with breast cancer.

The women had completed detailed annual questionnaires about their levels of physical activity from age 12 on and the researchers found that the incidence rates for invasive breast cancer dropped from 194 cases per 100,000 person-years in the least active women to 136 cases in the most active.

The levels of physical activity reported by the most active women were the equivalent of running 3.25 hours a week or walking 13 hours a week and the benefit was not linked to a particular sport or intensity, but related to total activity.

Professor Colditz says women don't have to be marathon runners to get the risk-reducing benefits of exercise but the more activity, the greater the benefit.

It is thought that the lower risk of breast cancer among active young women is because exercise reduces exposure to estrogens and research has shown that the more estrogen a woman is exposed to, the greater her risk for breast cancer.

Also women who begin menstruating later or enter menopause early, have a lower risk of breast cancer and young women who are physically active are more likely to start their periods later and less likely to have regular cycles when they begin their periods.

Breast cancer is the leading cause of cancer death among women worldwide, and kills an estimated 465,000 women each year; about 1.3 million women are diagnosed annually worldwide.

The research was funded by grants from the National Cancer Institute and the American Cancer Society.