October 7, 2013 | 2 minute read

Research already shows that physical activity reduces the risk of postmenopausal breast cancer. Now a new study attempting to better understand this link has found that walking for an hour a day reduces a woman’s risk, regardless of your weight, estrogen use or other factors linked with increased risk.

The study was published in Cancer Epidemiology, Biomarkers & Prevention.

As previous research has shown, this study found that more activity offers more protection for postmenopausal breast cancer.

For the study, researchers gathered data from almost 74,000 women who were ages 50 to 74 when they enrolled 19 to 20 years ago. At the start, the women answered questions about their activity habits, weight, hormone use and other risk factors. They updated the information periodically until the study ended in 2009. By that time, 4,760 women were diagnosed with breast cancer.

Almost one of every ten women reported they were not active at all. Almost half said walking was their only recreational activity.

The authors translated the women’s tennis, jogging and other activities into metabolic equivalent, or METs, a measure for how much energy your body uses for the activity. Women who were the most active – those with at least 42 MET hours per week – had a 25 percent lower risk for breast cancer compared with the least active, women with less than seven MET hours per week. A woman in the highest MET group would be jogging about an hour a day, for example.

When looking at the women who only walked, walking for seven hours or more per week linked to a 14 percent lower risk for breast cancer, compared with those who walked for three hours or less.

The link to lower risk applied to both estrogen-receptor positive (ER+) and negative (ER-) breast cancers.

The lower risk remained the same among women who were overweight or obese, and those who had gained weight as adults — at least 35 pounds. AICR’s report and its continuous updates found that both of these factors increase postmenopausal breast cancer risk. The link also held among women who had taken postmenopausal hormones, other factors linked with increased risk.

AICR’s reports concluded that moderate levels of physical activity, avoiding alcohol and staying a healthy weight all lower postmenopausal breast cancer risk. You can read more about breast cancer prevention on our website.