Sedentary behavior and the risk of breast cancer: findings from a Nigerian case–control study

While the role of physical activity in breast cancer (BC) risk has been reported in a few available studies from sub-Saharan Africa (SSA), the independent role of sedentary behavior hypothesized as differing from physical inactivity has not been investigated in the region. The purpose of this study was to investigate the relationship between sedentary behavior and BC risk in Nigeria.

The study was a case–control design involving 379 histologically confirmed BC cases and 403 cancer-free controls from five public hospitals across Nigeria. The participants were interviewed in person using a pretested and validated questionnaire. Sedentary behavior was measured as the self-reported number of hours of sitting per week (hours/week) associated with occupation, religious activity, and watching television (TV). Data were analyzed using multivariable logistic regression based on SPSS software, adjusting for relevant confounders.

Total sedentary time (OR [≥ 44.5 hours/week vs, < 27.50 hours/week] 1.77, 95% CI: 1.05, 2.98) was associated with increased BC risk. Every additional hour/week of sitting was associated with 2% (95% CI: 0%, 4%, p for trend = 0.033) increased BC risk among women with estrogen receptor-negative (ER–) BC. Occupational sedentary time (OR [≥ 23.4 hours/week versus < 12 hours/week] 1.70, 95% CI: 1.02, 2.85) and time spent watching TV were also associated with increased BC risk.

The number of hours of sitting was independently associated with increased BC risk. Reducing sedentary time, in both occupational and domestic settings, will potentially contribute to a decreased risk of BC in Nigeria.