Adherence to lifestyle-related cancer prevention guidelines and breast cancer incidence and mortality

Purpose: Breast cancer is the most common cancer in women. Many lifestyle factors have been associated with an increased risk of breast cancer incidence and mortality. An index-based approach to analyzing adherence to American Cancer Society (ACS) guidelines as a whole may better explain associations between lifestyle variables and breast cancer incidence and mortality. Methods: We created an index based on American Cancer Society–specific guidelines, including body mass index (BMI), physical activity, alcohol intake, tobacco use, daily time spent watching television, and certain dietary habits. Cox proportional hazards regression was used to model the association between the lifestyle index and primary breast cancer and breast cancer–specific mortality in the National Institutes of Health-American Association of Retired Persons (NIH-AARP) cohort. Results: We identified 7088 women with incident breast cancer, 1162 deaths overall, and 462 deaths due to breast cancer. Compared with the lowest quintile of lifestyle index score (meeting fewest guidelines), women in the highest quintile had a 24% lower risk of breast cancer (hazard ratio [HR] = 0.76, 95% CI: 0.70, 0.82) and 37% lower risk of all-cause mortality (HR = 0.63, 95% CI: 0.53, 0.76), while the association with breast cancer-specific mortality was nonsignificant. Conclusions: Healthier prediagnosis lifestyle is associated with a decreased risk of breast cancer and all-cause mortality in the NIH-AARP cohort.