A study of more than 3,000 women from Long Island, N.Y., found that women who engaged in 10 to 19 hours of at least mild exercise per from their reproductive years on had about a 30 percent lower risk of developing breast cancer. The effects of physical activity were strongest among postmenopausal women, based on the data analysis.
The women were between the ages of 20 and 98 who participated in the Long Island Breast Cancer Study Project, a series of government-funded studies conducted to investigate possible environmental contributors to breast cancer on Long Island. The women were also predominantly white and upper middle class.
"We didn't see a risk reduction during the time before the first birth," said lead author Lauren McCullough, a doctoral candidate at the UNC Gillings School of Public Health. "There is a strong association seen with postmenopausal women, which is totally in line with other studies."