An epidemiologic investigation of physical activity and breast cancer risk in Africa.

BACKGROUND: Physical activity (PA) is modifiable and linked to decreased breast cancer risk but its impact has not been investigated among indigenous African populations. METHODS: From 2011 to 2013, 558 cases and 1,014 controls were recruited into the African Breast Cancer Study in Nigeria, Cameroon, and Uganda, and completed a culturally tailored PA questionnaire that assesses habitual PA the year before diagnosis/interview. PA sub-scores (housework, occupational, and leisure PA) and a total PA score were calculated (metabolic equivalent of task, MET-hours/day). Multiple logistic regressions were performed, adjusting for age, body mass index (BMI), study sites, and menopausal status. The models were then stratified by BMI and study site, respectively. RESULTS: The overall PA score among controls (17.8 MET-hours/day on average) was mainly composed by housework PA and occupational PA with little leisure PA (7.0, 10.3, and 0.5 MET-hours/day, respectively). Multivariable analyses showed that PA was significantly associated with reduced breast cancer risk in both pre- and postmenopausal women (up to 60% risk reduction), with a dose-responsive relationship (Ptrend < 0.001). The inverse association was strong among lean women, less strong but still significant among overweight women, but not existing among obese women. The inverse association held for all intensity-level and domains of PA. CONCLUSIONS: PA of African women mainly consists of housework and work-related activities. The preliminary data show that PA may be significantly associated with reduced breast cancer risk. IMPACT: An inverse association between PA and breast cancer risk was observed among indigenous African women, a unique and understudied population.

Alcohol consumption and breast cancer risk among women in three sub-Saharan African countries.

BACKGROUND: Alcohol drinking is linked to the development of breast cancer. However, there is little knowledge about the impact of alcohol consumption on breast cancer risk among African women. METHODS: We conducted a case-control study among 2,138 women with invasive breast cancer and 2,589 controls in Nigeria, Cameroon, and Uganda from 1998 to 2013. A structured questionnaire was used to collect information on alcohol consumption, defined as consuming alcoholic beverages at least once a week for six months or more. Logistic regression was used to estimate adjusted odds ratio (aOR) and 95% confidence interval (CI). RESULTS: Among healthy controls, the overall alcohol consumption prevalence was 10.4%, and the prevalence in Nigeria, Cameroon, and Uganda were 5.0%, 34.6%, and 50.0%, respectively. Cases were more likely to have consumed alcohol (aOR = 1.62, 95% CI: 1.33-1.97). Both past (aOR = 1.54; 95% CI: 1.19-2.00) and current drinking (aOR = 1.71; 95% CI: 1.30-2.23) were associated with breast cancer risk. A dose-response relationship was observed for duration of alcohol drinking (P-trend <0.001), with 10-year increase of drinking associated with a 54% increased risk (95% CI: 1.29-1.84). CONCLUSION: We found a positive relationship between alcohol consumption and breast cancer risk, suggesting that this modifiable risk factor should be addressed in breast cancer prevention programs in Africa.