Older women who take regular walks are less likely to get breast cancer than their less-active peers, according to a new study.
American Cancer Society (ACS) researchers found postmenopausal women who walked for at least one hour each day had a 14 percent lower chance of getting breast cancer than infrequent walkers. More vigorous exercise was tied to an even lower risk.
"The exciting piece about this is that you don't need to be a marathon runner to lower your risk of breast cancer," Alpa Patel, the study's senior author, said.
"Just going for a one-hour walk a day could have a significant impact on lowering your risk," Patel, a senior epidemiologist at ACS in Atlanta, added.
Dozens of past studies have found links between physical activity and breast cancer, but left some unanswered questions, write Patel and her fellow researchers in the American Association for Cancer Research's journal Cancer Epidemiology, Biomarkers and Prevention.
For example, those studies didn't answer whether women still benefit from walking if they are overweight or taking hormones to treat menopause symptoms, like hot flashes.
For the new study, the researchers used data on about 74,000 women between the ages of 50 and 74.
Beginning in 1992, the women were asked questions about their health, medications and exercise habits. They also reported how much exercise they got in 1999, 2001 and 2005.
Between 1992 and 2007, about 6.5 percent of all women in the study were diagnosed with breast cancer.
The researchers found that women who walked at a moderate pace for at least seven hours each week were 14 percent less likely to be diagnosed with breast cancer, compared to those who walked for three hours or less each week.
The difference translates to roughly one fewer woman in 1,000 getting breast cancer each year.
"When we talk about moderately paced walking, we're talking about a pace of about three miles per hour," Patel said.
Her team also found women who exercised more vigorously for at least seven hours per week were about 25 percent less likely to be diagnosed with breast cancer, compared to women who participated in those activities less often.
Patel told Reuters Health that walking and vigorous exercise were tied to a reduced breast cancer risk even among women who were overweight or taking hormone therapy.
"I would say this is encouraging news for all women who want to begin an exercise regimen but find it overwhelming," she said.
The study can't prove walking prevented any cancers. But the researchers say it could be that walking affects a woman's hormones, insulin resistance, weight and other factors linked to breast cancer risk.
The US Centers for Disease Control and Prevention currently recommends that adults get at least two and a half hours of moderate exercise per week. Alternatively, it recommends at least one hour and 15 minutes of vigorous activity per week.
Less than half of US women report meeting those recommendations, however.
Dr. Steven Chen, an associate professor at City of Hope in Duarte, California, said women can add an hour of walking throughout the day.
"You can pick up 10 minutes at the grocery store, another 10 minutes when you're out shopping or another 10 or 15 minutes at work… You can pick up your hour pretty quickly," Chen, who wasn't involved with the new study, told Reuters Health.
He pointed out that sitting was also tied to a woman's risk of breast cancer in the study.
"The more you sit, the higher the likelihood of you developing cancer," he said. "So of course we encourage people to be as active as they can."