Abstract B30: Indicators of energy balance and breast cancer risk among white and black women
Authors: Sanderson Maureen , Deming-Halverson Sandra L. , Fair Alecia M. , Shrubsole Martha J. , Beeghly-Fadiel Alicia , Nechuta Sarah , Cui Yong , Shen-Miller David , O'Hara Heather , Foderingham Nia , Shu Xiao-Ou , Zheng Wei 
Published: May 2015

Introduction: Physical activity has been linked to reduced breast cancer risk, especially among women diagnosed postmenopausally. Since the majority of studies of this association have been conducted in white women, we used the Nashville Breast Health Study (NBHS) to determine whether similar effects were seen in black women.

Methods: The NBHS is a population-based case-control study of breast cancer among women age 25 to 75 conducted between 2001 and 2010 in and around the Nashville Metropolitan area. Telephone interviews were completed with 1,866 incident breast cancer cases ascertained through hospitals and the statewide cancer registry, and 2,306 randomly selected controls (with respective response rates of 58% and 79%).

Results: A greater percentage of white (premenopausal 59%, postmenopausal 54%) than black (premenopausal 51%, postmenopausal 43%) women reported they had engaged in leisure-time physical activity or exercise in the past 10 years. Among premenopausal white and black women, there was little effect of exercise on breast cancer risk; however, occupational activity, defined as standing and walking at work, was associated with an increased risk of breast cancer. After adjusting for confounding and dividing the group of women who had engaged in exercise into tertiles (MET hours per day), there was a suggested reduction in postmenopausal breast cancer in women of both races (highest tertile relative to none - white odds ratio [OR] 0.8, 95% confidence interval [CI] 0.6-1.0, p for trend=0.058; black OR 0.7, 95% CI 0.4-1.1, p for trend=0.098). Similar point estimates were found for occupational activity. When considering the joint effects of caloric intake, obesity and weight gain since age 18 on the association of exercise and breast cancer, the greatest effect was seen for weight gain since 18 with increased risks in most categories relative to women in the highest tertile of exercise who had lost or maintained weight. This pattern was most pronounced among white women diagnosed postmenopausally, but among black women diagnosed premenopausally.

Discussion: Our results indicate that although postmenopausal black women report engaging in very little leisure-time physical activity, its' effect on breast cancer risk is comparable to white women. However, the joint effect of adult weight gain on the exercise and breast cancer association may differ by race and menopausal status. White and black women should be encouraged to engage in leisure-time physical activity regardless of the amount of work- and housework-related physical activity done to help reduce their risk of breast cancer and other chronic diseases.

Citation Format: Maureen Sanderson, Sandra L. Deming-Halverson, Alecia M. Fair, Martha J. Shrubsole, Alicia Beeghly-Fadiel, Sarah Nechuta, Yong Cui, David Shen-Miller, Heather O'Hara, Nia Foderingham, Xiao-Ou Shu, Wei Zheng. Indicators of energy balance and breast cancer risk among white and black women. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr B30. doi:10.1158/1538-7755.DISP13-B30