Healthy lifestyle behaviours protective against breast cancer in postmenopausal women

Postmenopausal women who engage in healthy lifestyle behaviours appear to have a reduced risk of breast cancer, regardless of race and ethnicity and hormone receptor status, according to a study.

The multiethnic cohort study included 65,561 African American, Japanese American, Latina, Native Hawaiian, and White postmenopausal women. A Healthy Lifestyle Index (HLI) score was calculated for each participant. The HLI score consisted of seven components, including diet quality, physical activity, sedentary behaviour, smoking status, alcohol consumption, BMI, and sleep duration.

Multivariable Cox proportional hazards models were used in the analysis. The Wald test was applied to evaluate multiplicative interaction by race and ethnicity, as well as heterogeneity of effect by hormone receptor status.

Over a mean follow-up of 19.2 years, 4,555 incident cases of invasive breast cancer were recorded. Healthy lifestyle behaviours were associated with a 5-percent reduction in the risk of postmenopausal breast cancer risk (adjusted hazard ratio [aHR], 0.95, 95 percent confidence interval [CI], 0.94–0.97; p<0.0001). Compared with the first tertile of HLI scores, the second and third quartiles were associated with an 8-percent and 19-percent risk reduction (aHR, 0.92, 95 percent CI, 0.85–0.99 and aHR, 0.81, 95 percent CI, 0.75–0.87, respectively; p<0.01 for trend), with similar risk reductions observed across racial and ethnic groups.

Results were consistent for the risk of hormone receptor–positive breast cancer, with healthy lifestyle behaviours having a protective effect (p<0.01). Meanwhile, no significant associations were observed for hormone receptor–negative breast cancer.