Association of leisure time physical activity with breast cancer risk and breast cancer sub-types in Nigerian women.

Abstract

e13085 Background: The association between physical activity and breast cancer has not been studied among Nigerian women and in particular by breast cancer sub-types. Therefore are studies aims are to examine the association between leisure time physical activity (LTPA) and breast cancer in Nigerian women and to examine the association between LTPA and estrogen receptor positive (ER+), triple negative breast cancer (TNBC+), Luminal A breast cancer in Nigerian women. Methods: We enrolled 739 newly diagnosed primary invasive breast cancer and 739 age-matched controls in Nigeria from 01/2014 to 07/2016. This analysis is restricted to the 40% of cases for whom we have complete ER, TNBC and Luminal-A data and their matched controls. We derived the average amount of time per week spent on LTPA over the past one year using a modified Nurses’ Health Study II PA questionnaire. LTPA was calculated from the total metabolic equivalent (METs) assigned for each reported physical activity hour/week (i.e. walking, cycling, and dancing). We examined LTPA by comparing participants who attained the WHO physical activity recommendations of at least 150 minutes of moderate-intensity or/and 75 minutes of vigorous-intensity aerobic activity weekly with those who did not. We used conditional logistic regression to estimate the adjusted Odds Ratio (OR) of LTPA and overall as well as subtypes of breast cancer. Results: The mean (SD) age of cases was 41.6 (9.1) and controls was 43.9 (11.8) years. Women who attained the WHO physical activity recommendations had 43% decreased risk of breast cancer (OR = 0.57 95% CI:0.42-0.77) compared with those who did not, after controlling for demographic, anthropometric and fertility related factors. LTPA was also associated with reduced risk of breast cancer subtypes by 41% for ER+, 59% for TNBC+ and 59% for Luminal A. Conclusions: Physical activity is associated with reduced risk of breast cancer overall and by subtypes in Nigerian women.