Leisure-Time Physical Activity is Associated with reduced Risk of Breast Cancer and Triple Negative Breast Cancer in Nigerian Women

Abstract Background: Physical activity (PA) is associated with reduced risk of breast cancer and its various subtypes but this association is less well described in African women, particularly in women with triple-negative breast cancer that is more common in Sub-Saharan Africa. In this study, we examined the associations between leisure-time physical activity (LTPA) and breast cancer in total and by subtypes in Nigerian women.Methods: We studied 472 newly diagnosed primary invasive breast cancer patients age-matched (±5years) with 472 controls from the Nigerian Integrative Epidemiology of Breast Cancer (NIBBLE) Study enrolled from January 2014 to July 2016. We derived the average amount of time spent on LTPA per week over the past year using a modified Nurses’ Health Study-II physical activity questionnaire. We calculated the total metabolic equivalents (METs) for each reported LTPA per hour/week (i.e. walking, cycling, and dancing) and compared odds of breast cancer among participants who attained the World Health Organization (WHO) physical activity(PA) recommendations of at least 150 minutes of moderate-intensity or/and 75 minutes of vigorous-intensity aerobic activity/week with those who did not. In addition, we evaluated these by categories of LTPA in quartiles of METs. We used conditional and unconditional logistic regression models to estimate the adjusted Odds Ratio (OR) of LTPA for overall breast cancer and by molecular subtypes. Results: The mean age (SD) of cases, 44.4 (10.0) years, was similar to that of controls, 43.5 (9.5) after matching. The OR for breast cancer among women who attained the WHO PA recommendations compared with those who did not was 0.64 (95% CI: 0.45-0.90). LTPA was associated with 51% reduced odds of hormone receptor-positive and 65% reduced odds of triple-negative breast cancer. We observed a significant dose-response relationship where women with high levels of LTPA had lower odds of overall breast cancer, triple-negative and hormone receptor-positive breast cancer. Conclusions: Increasing LTPA in African women may play a significant role in reducing the incidence of breast cancer, particularly of the more aggressive subtype as triple-negative, which is more prevalent in Sub-Saharan Africa.