New study: increased physical activity reduces breast cancer risk

A study of over 100,000 women found that increasing physical activity and reducing time spent in a sitting position can reduce the risk of breast cancer.
An international team of researchers from Australia, the UK and the US used genetic analysis to establish a causal relationship between overall activity levels and cancer risk.

a published study British Journal of Sports MedicineIt included data from 130,957 women, 76,505 of whom had breast cancer.
While previous studies have shown an association between physical activity and a reduced risk of breast cancer, proving a causal relationship has been difficult.

Senior author of the study, Assoc. Dr. “There has always been uncertainty as to whether physical activity actually causes lower breast cancer rates or whether this association is confounded with other factors,” said Bridget Lynch.

“Women who tend to be more physically active, for example, can lead healthier lives in other ways as well,” Lynch said.
According to the scientist, the new study “suggests this is a strictly causal effect: physical activity reduces the risk of developing breast cancer.”
“We saw a reduction in the risk of all types of breast cancer,” said the study author.

The researchers used a technique known as Mendelian randomization to establish a causal relationship that uses genetic variants for certain traits—in this case, physical activity and time spent sitting or lying down.

They found that higher levels of physical activity or general movement were associated with a 41% lower risk of invasive breast cancer.

In premenopausal and postmenopausal women, vigorous physical activity at least three days a week was associated with a 38% lower risk of breast cancer compared to no active physical activity.

“For every 100 minutes of sedentary time per day, we found a 20 percent increase in overall breast cancer risk and a double in triple-negative breast cancer risk (more aggressive and difficult to treat),” Lynch said.
Physical activity is thought to reduce the risk of breast cancer because it reduces the amount of estrogen and androgen hormones circulating in the bloodstream. Reducing inflammation during exercise may also be an additional factor in the fight against cancer.