More Evidence That Exercise, Including Walking, Reduces Risk

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A large study done by the American Cancer Society has found that regular exercise at a moderate intensity level, such as walking, reduces breast cancer risk in postmenopausal women.

The study was published online on Oct. 4, 2013 by Cancer Epidemiology, Biomarkers, and Prevention. Read the abstract of “Recreational Physical Activity and Leisure-Time Sitting in Relation to Postmenopausal Breast Cancer Risk.”

Many studies have shown a link between exercising at a vigorous intensity level, such as running or doing aerobics, and a lower risk of breast cancer. But it hasn’t been clear if doing only moderate intensity activities, such as walking, offered this same benefit.

This study was part of the Cancer Prevention Study-II Nutrition Cohort, a prospective study on cancer incidence. A prospective study follows a group of similar people who are different in terms of the factors that are being studied to see how the factors affect rates of a certain outcome. In this case, the researchers looked at 73,615 postmenopausal women to see how various levels of exercise affected breast cancer rates.

When the study started in 1992, the women completed a survey that asked about a number of factors, including demographic information, medical history, and exercise. They filled out follow-up surveys every 2 years between 1997 and 2009.

The surveys specifically asked about how many hours the women spent on physical activities such as walking, jogging, swimming, playing tennis, bicycling, and performing aerobic exercises every week, as well as the number of hours spent in leisure time sitting, including watching television and reading:

  • about 9% of the women didn’t do any type of physical activity
  • 47% of the women said walking was their only physical activity

The median activity level was 3.5 hours of moderately paced walking per week. This means that half the women did more exercise than that and half the women did less.

During the study, 4,760 (6.5%) women developed breast cancer.

Among the women who said walking was their only physical activity, women who walked at least 7 hours per week had a 14% lower risk of breast cancer compared to women who walked 3 or fewer hours per week.

The most active women had a 25% lower risk of breast cancer than the least active.

The links between physical activity and lower breast cancer risk weren’t affected by body mass index, weight gain, or using hormone replacement therapy. Time spent sitting also didn’t affect breast cancer risk.

“We were pleased to find that without any other recreational activity, just walking an average of 1 hour per day was associated with a lower risk of breast cancer in these women,” said Alpa Patel, Ph.D., senior epidemiologist at the American Cancer Society in Atlanta, Ga. “More strenuous and longer activities lowered the risk even more.”

Along with a healthy diet and lifestyle choice, regular exercise is one of the best things women can do to keep breast cancer risk as low as it can be. This study is encouraging because it suggests that walking -- something many women are comfortable doing -- can help lower breast cancer risk.

To fit in an hour of walking per day, it may help to break up the walking into two 30-minute sessions. Maybe you walk for 30 minutes before you go to work and another 30 minutes on your lunch break. Or make plans to walk with a friend after work -- you’re more likely to stick to it if someone else is counting on you. Plus, you get to socialize and ease the day’s stresses. Regular exercise also helps keep your physical and mental health in top shape. No matter how old you are, it’s never too late or too soon to get moving.

Visit the Breastcancer.org Exercise pages for tips on exercising safely and how to stick to an exercise routine.

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