Regular physical activity is known to reduce breast cancer risk by about 25%. This estimate is based on studies that recorded the number of hours per week women spent exercising and doing other physical activities. New results from the US National Runners’ and Walkers’ Health Studies suggest that the benefits of meeting exercise recommendations may be even greater, with small amounts of regular exercise potentially lower the risk of dying from breast cancer by more than 40%.
The research is the latest big-data publication by Paul Williams, Ph.D., whose work has shown the health benefits of running and walking in areas such as hypertension, all forms of cancer, and even cataracts. For this study, published in the online journal PLoS One, Williams looked at breast cancer mortality in 79,124 women during the 11 years following their baseline survey. None of the women had a history of breast cancer before entering the study. The women reported the distances they walked or ran each week.
During the study’s 11 years, 111 women died from breast cancer. Those who met the current exercise recommendations were at 41.5 % lower risk for breast cancer mortality compared to those who fell short of the recommendations.
It didn’t take much working out to reap such dramatic benefits – the protective dose of exercise generally corresponded to about 11 kilometres of brisk walking or 7.65 kilometres per week of running. “The protective benefits of exercise may be even greater than previously believed,” Williams said. “This paper highlights yet another important benefit of regular exercise in women.”
Williams also looked at whether larger-breasted women runners and walkers were at greater risk for breast cancer mortality. Previous research has yielded somewhat mixed results, with a few studies showing an association between larger breast volume and breast cancer, while others showing none. The women reported their bra-cup size along with their overall body weight and height, and other established risk factors.
Williams reported that, compared to A-cup women, those with a C-cup were at a four times greater risk for breast cancer mortality, and those with a D-cup or larger at 4.7 times greater risk. Lean, athletic women who are larger breasted may be at greater risk for breast cancer mortality because their larger breasts may contain less fat and more of the epithelial cells that may become cancerous, Williams said.
