It’s long been known that women who are more physically active in their spare time have a lower risk of breast cancer, with those who are the most active having about 20 percent less risk of developing the disease.
Now, researchers at Columbia University have found that how recreationally active women are as girls may be tied to what kind of tissue is in the breast and markers of stress that enhance risk for breast cancer: the most common cancer in women.
Girls who reported getting in at least two hours of such activity in the prior week had an indicator of lower breast density and reduced concentrations of stress markers in their urine, a new study of nearly 200 of Black and Hispanic New Yorkers found.
The findings, based on assessments of girls recruited between 1998 and 2006, follow past research in women showing that higher levels of physical activity were tied to lower breast density, the researchers said.
“Our findings suggest that recreational physical activity is associated with breast tissue composition and stress biomarker changes in adolescent girls, independent of body fat, which could have important implications for breast cancer risk,” Dr. Rebecca Kehm, an assistant professor of epidemiology at Columbia Mailman School of Public Health, said in a statement.
The study
The average age of girls included in the study was 16 years old and more than half identified as Hispanic.
The girls reported their own activity levels, and more than half said they had no recreational physical activity in the past week.
Close to three-quarters reported no participation in organized activities, and 66 percent had no participation in unorganized activities.
The girls also gave blood and urine samples and underwent tissue assessments during visits to Columbia.
“We measured biomarkers of stress and chronic inflammation that are widely validated and commonly used in epidemiologic research, enhancing confidence in our findings,” said Dr. Mary Beth Terry, another epidemiology professor, said.
More research is needed to determine how markers in adolescents may become breast cancer risk later in life.
What does breast density have to do with it?
Dense breast tissue is when your breasts have more fibrous and glandular tissue and less fatty tissue. It affects about half of women, according to the Cleveland Clinic.
Breast density forms in adolescence, driven by hormones, and is a key indicator of breast cancer risk. Having denser breasts heightens risk for the disease — although it’s not fully understood why.
Having dense breast tissue also makes it harder to see something concerning on a mammogram, but does not increase the risk of dying of breast cancer.
Water content in breasts is an indicator of density, with higher water content indicative of higher density.
The girls who got at least two hours of recreational physical activity in the prior week had lower water content.
A rising problem
The findings come as breast cancer rates are rising in the U.S. among adults under the age of 50.
While the number of early cases has ticked up steadily over the past two decades, researchers reported a sudden and unexplained spike in 2016.
In 2000, there were 64 cases per 100,000 people, with rates increasing 0.24 percent each year for the next 16 years. But between 2016 and 2019, there was a 3.76 percent surge, according to doctors at Washington University in St. Louis.
This year, physicians expect more than 321,000 new cases and more than 42,000 deaths in women of all ages.
Women who are Black and Hispanic are disproportionately at risk at younger ages, as well, according to Kehm.
“At the same time, Black and Hispanic girls consistently report lower levels of recreational physical activity than their non-Hispanic white peers,” she pointed out.
