Exercise may cut premenopausal breast cancer risk

By Will Dunham

WASHINGTON (Reuters) - Regular exercise in adolescence and young adulthood may help cut a woman's risk of developing breast cancer before menopause, according to a U.S. study published on Tuesday.

The women who were the most physically active were 23 percent less likely to develop premenopausal breast cancer than the women who got the least exercise, the researchers wrote in the Journal of the National Cancer Institute.

High levels of exercise from ages 12 through 22 contributed the most to the protective effect, the researchers said.

"The more activity, the greater the benefit," study leader Dr. Graham Colditz of Washington University School of Medicine and Barnes-Jewish Hospital in St. Louis said in a telephone interview.

Previous studies showed that regular exercise in adulthood leads to at least a 20 percent lower risk of breast cancer after menopause, the researchers said. Research on exercise and breast cancer risk before menopause had produced inconsistent results, they said.

The researchers said the new study indicated women need regular physical activity starting at a young age to comparably lower their risk of breast cancer before menopause. They called their study the largest and most detailed examination to date of the impact of exercise on early breast cancer risk.

Colditz and colleagues studied 65,000 registered nurses aged 33 to 51 who reported in 1997 how much leisure-time physical activity they had done since the age of 12.

After six years of follow-up, 550 of the women were diagnosed with breast cancer.