Although physical activity has been associated with a reduced risk of breast cancer risk in high income countries (HIC), its role has not been widely studied in sub-Saharan Africa. Our aim was to investigate the association between physical activity (PA) and the risk of breast cancer in Nigeria.
We conducted a hospital-based case-control study involving participants from five hospitals in Lagos and Abuja. Women were interviewed in-person between October 2016 and May 2017 using a semi-structured questionnaire. Total PA was estimated by summing occupational, household, transport and leisure PA scores. PA was summarised as metabolic equivalents (MET) hours per week (MET-hr/wk). The putative association between breast cancer incidence and PA was analysed using multivariable logistic regression.
379 histologically confirmed breast cancer cases and 403 controls took part. Compared to women in the lowest categories, women in the upper middle category of total PA(adjusted OR-AOR 0.44, 95% CI: 0.27, 0.78),uppermost categories of total non-vigorous PA (AOR 0.26, 95%CI:0.09,0.75), household PA(AOR 0.0.38, 95% CI: 0.20, 0.71) and occupational PA (AOR 0.64, 95% 0.40, 1.02) had a reduced risk of breast cancer following adjustment for relevant confounders. Transport and leisure PA were not significantly associated with a reduced risk of breast cancer.
The total effect of various PA related to regular activities of Nigerian women was associated with a reduced risk of breast cancer. PA especially at household and occupational environments should be promoted as part of breast cancer prevention strategy in Nigeria.
- • Total PA (mostly non-vigorous PA)was associated with a reduced risk of breast cancer.
- • This risk reduction was higher among premenopausal women, and women with low BMI.
- • Occupational and household PA independently reduced breast cancer risk.
- • Leisure PA was not associated with a reduced risk of breast cancer.
Breast cancer is the most frequently diagnosed cancer and leading cause of cancer deaths among women in Africa including Nigeria . Although the rising rate of new cases of the disease in places such as Nigeria is, in part, explained by population growth, the contribution of lifestyle factors such as low physical activity as a result of increasing urbanisation with its attendant rural -urban migration cannot be ruled out . Available studies have reported a prevalence rate of physical inactivity ranging from 26% to 57% in Nigeria .
There has been relatively little research on PA and breast cancer in sub-Saharan Africa (SSA). The African Breast Cancer Study (ABCS) comprising participants from Nigeria, Uganda and Cameroon observed an association between increased PA and a reduced risk of breast cancer . However, the Nigerian participants involved in that study were predominantly (80%) from one ethnic group in the southern region of the country. Sociocultural differences in gender roles across ethnic groups in Nigeria could affect lifestyle behaviours . There is a need, therefore, to explore the relationship between PA and breast cancer risk in a population that is more representative of the ethnic variability found in Nigeria. We investigated the association between PA and breast cancer risk including participants from the southern (Lagos) and northern part of Nigeria (Abuja).