Exercise Lowers Breast Cancer Risk in Younger Women
Pre-menopausal women who exercised more had a lower risk of breast cancer than women who exercised less, according to a large international study.
The research was published online on Dec. 11, 2023, by the Journal of Clinical Oncology. Read the abstract of “International Pooled Analysis of Leisure-Time Physical Activity and Premenopausal Breast Cancer in Women From 19 Cohorts.”
Why do the study?
Earlier research has shown that exercise reduces breast cancer risk in post-menopausal women. But studies in younger women have been limited and inconclusive. So the researchers decided to test that in a large study.
About the study
The researchers analyzed the relationship between physical activity and breast cancer risk in 547,601 women ages 35.2 to 45.8 years. All the women were pre-menopausal and lived in North America, Europe, Asia, and Australia.
Follow-up time ranged from 8 to 16 years.
The researchers recorded characteristics of the women linked to breast cancer risk, including BMI, age, age at first period, number of children, family history of breast cancer, use of birth control pills, smoking, and race/ethnicity:
35% of the women had a BMI of 25 or higher, which, according to current BMI interpretation, made them overweight or obese; but it’s important to know that using BMI to assess weight is considered problematic
75% of the women were age 35 or older when they joined the study
77% of the women had their first period at age 12 or older and 21% started their periods between the ages of 7 and 11
19% of the women had no children
11.5% of the women had a family history of breast cancer
76% of the women used birth control pills
59% of the women were current or former smokers
59% of the women were white, 8% were Black, 2.6% were Asian, 2% were Latina or Hispanic, and 30% were of other races and ethnicities or their race and ethnicity wasn’t known
Each week, the women reported how much time they spent doing leisure time physical activity, which was defined by the researchers as playing sports, exercising, and walking for recreation (as opposed to walking as part of the activities of daily living, including going to work, shopping, etc.).
Based on how much physical activity the women did and how vigorous it was, the researchers placed them into five categories, ranging from most active to least active. The women were evenly divided among the activity categories, with 20% in each.
During follow-up, 10,231 cases of invasive breast cancer or DCIS were diagnosed.
The researchers’ first analysis found that women who were the most active had a 6% lower risk of breast cancer compared to women who were the least active.
When the researchers accounted for differences in BMI – excess weight is a risk factor for breast cancer – women who were the most active had a 10% lower risk of breast cancer.
Both of these differences were statistically significant, which means that they were likely due to the difference in physical activity and not just because of chance.
The researchers also looked to see if physical activity reduced the risk of certain types of breast cancer more than others. They found that women with the highest levels of physical activity had a 43% lower risk of HER2-positive breast cancer. This difference also was statically significant.
“This large, pooled analysis of cohort studies adds to evidence that engagement in higher levels of leisure-time physical activity may lead to reduced premenopausal breast cancer risk,” the researchers wrote.
What this means for you
The results of this study underscore what other studies have found: Being active reduces your risk of breast cancer.
If you don’t like to exercise or have trouble fitting it into a busy schedule, a study published in July 2023 offers encouraging news: Three to four minutes of vigorous exercise a day – like doing jumping jacks – seems to lower cancer risk.
Finding the motivation and time to exercise nearly every day can be hard, especially when you have to balance it with all the other things you have to do.
Starting slowly and then gradually increasing the time and intensity you exercise can help, especially if you’ve never exercised before. Walking for 15 to 20 minutes a day can be a good way to start. Slow bike riding or gentle stretching are also good ways for beginners to start moving.
Walking or doing another type of exercise with a friend can give you the motivation you need to carve out some time to be active each day. Plus, you can socialize at the same time. It’s never too late to get moving. And once you start, keep at it!
For motivation, listen to The Breastcancer.org Podcast episode with Dr. Christina Dieli-Conwright discussing her research on exercise as medicine. Besides talking about all the benefits of exercise, she also offers some tips on how to get started with exercise and how to stay motivated.
To help you start, our friends at Living Beyond Breast Cancer, in collaboration with cancer exercise specialist Sami Mansfield, have developed the BeACTive workouts especially for people who’ve been diagnosed with breast cancer, but the program can help anyone start to be more active.
— Last updated on March 9, 2024 at 9:32 PM