Exercise Reduces Risk, but Benefits Disappear if Women Stop Exercising

Many studies have found a link between regular exercise and a lower risk of being diagnosed with breast cancer or breast cancer coming back (recurrence). As a result, the American Cancer Society and many doctors recommend that women who’ve been diagnosed with breast cancer, as well as those who haven’t, exercise regularly — about 4 to 5 hours per week at a moderate intensity level. (Brisk walking is considered moderate intensity exercise.)

While the link between regular exercise and lower breast cancer risk has been well-documented, doctors haven’t been sure how long a woman has to exercise before the benefits start. Doctors also haven’t been sure how long the benefits lasted if a woman stopped exercising.

A French study has found that postmenopausal women who exercised regularly in the last 4 years had a lower risk of breast cancer than postmenopausal women who exercised less during the 4 years. The researchers also found that postmenopausal women who had exercised regularly between 5 and 9 years earlier but were less active in the past 4 years didn’t have a lower risk of breast cancer.

The study was published online on Aug. 11, 2014 by the journal Cancer Epidemiology, Biomarkers & Prevention. Read the abstract of “Recent Recreational Physical Activity and Breast Cancer Risk in Postmenopausal Women in the E3N Cohort.”

The E3N cohort is a group of 100,000 French women who were 40 to 65 years old when the study started in 1990. The study is looking at risk factors for cancers that develop primarily in women, including breast and ovarian cancers. The women in the cohort answer surveys every 18 months.

In this study, the researchers looked at information on exercise from 59,308 postmenopausal women who were part of the cohort from 1993 to 2005. The women had been postmenopausal for about 8.5 years.

Women who regularly exercised in the previous 4 years — the equivalent of walking about 4 hours per week (or cycling or doing more intense exercise 2 hours per week) – had a 10% lower risk of breast cancer than women who exercised less than that.

This lower risk wasn’t affected by body mass index, weight gain, waist circumference, or how much the women exercised 5 to 9 years earlier.

Still, the researchers also found that if women stopped exercising, the risk-reducing benefits quickly disappeared. Women who exercised the equivalent of walking 4 hours per week between 5 and 9 years earlier but weren’t as active in the past 4 years didn’t have a lower risk of breast cancer.

“Postmenopausal women who exercise should be encouraged to continue and those who do not exercise should consider starting because their risk of breast cancer may decrease rapidly,” said Agnès Fournier, a scientist at the Centre for Research in Epidemiology and Population Health at the Institut Gustave Roussy in France and lead author of the study.

So the bottom line is keep using it or lose it.

If you’re busy with work, household chores, and family matters, finding time to exercise almost every day can be hard.

It can help to break up your exercise into 20- or 30-minute sessions that add up to about 4 hours per week. Walking is a great way to start. Maybe you walk 30 minutes before going to work and 20 minutes on your lunch break. You can add a few more minutes by parking farther away from your building or taking mass transit. Or you can make plans to walk with a friend after work — you’re more likely to stick with exercise if someone else is counting on you. Plus, you can socialize at the same time.

Along with a healthy diet and lifestyle choices, regular exercise is one of the best things women can do to keep the risk of a first-time breast cancer or recurrence as low as it can be. This study adds to other research suggesting that regular exercise reduces breast cancer risk. 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. And once you do start, keep at it!

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