Abstract C049: The association between breast cancer and physical activity levels by race in a prospective cohort study
Authors: Stahr Shelbie , Runnells Gail , Rogers Lora , Mcelfish Pearl , Kadlubar Susan , Su Joseph L. 
Published: August 2020

Background: Although the relationship between physical activity and breast cancer is well established, research demonstrating levels of physical activity and breast cancer association among different racial groups is less definitive. It is perceived by the public that beneficial effects of physical activity depend on the rigorousness of activity performed, and within these levels of physical activity, racial differences are observed.

Objectives: The aim of this study is to evaluate levels of physical activity among different racial groups, while stratifying for menopause status, and their relationship to breast cancer. Specifically examining incidence and prevalent breast cancer cases, this study examined potential variation of physical activity in relation to time of cancer diagnosis among different racial groups.

Methods: A cohort of 26,387 women in the Arkansas Rural Community Health Study (ARCH) was used to evaluate physical activity and its association with breast cancer among different racial groups. Multiple logistic regression (OR, 95%CI) was used to examine the association between breast cancer and intensity, length, and frequency of physical activity while adjusting for confounding variables, such as age and parity. Demographic and weekly physical activity information was reported at baseline. A Metabolic Equivalent of Task score was derived from the self-reported questionnaire data.

Results: A total of 1,455 participants were excluded due to insufficient information regarding breast cancer status, race, and menopausal status, resulting in a sample of 23,980 participants. The analysis consisted of 155 newly diagnosed breast cancer cases after the baseline (incident), 2,330 existing breast cancer cases when entering the study (prevalent), and 21,495 noncancer subjects, of whom 78% identified as European American (EA) and 22% identified as African American (AA). Approximately 49% of eligible participants reported being postmenopausal and 51% being premenopausal. A significant downward trend was observed in vigorous physical activity among EA women for incident and prevalent breast cancer (p= 0.002 and 0.04), whereas no clear trend was seen among AA women due to small sample size. Similar trends can be seen in vigorous physical activity postmenopausal EA women (p= 0.005 and 0.002). The beneficial association was not observed among AA women. On the other hand, overall physical activity appears to be positively associated with breast cancer among AA women (p for trend = 0.04).

Conclusions: There appears to be a beneficial effect of vigorous physical activity and breast cancer among EA, regardless of pre- or postmenopausal status. However, the effect does not seem to apply to AA women, which could be the result of small number of breast cancer cases in African Americans. The current physical activity recommendations may not be applicable to all racial groups. We may be able to get a better race-specific recommendation regarding the level of leisure physical activity by pooling our data with other studies.

Citation Format: Shelbie Stahr, Gail Runnells, Lora Rogers, Pearl Mcelfish, Susan Kadlubar, Joseph L. Su. The association between breast cancer and physical activity levels by race in a prospective cohort study [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr C049.