Differences in hypertension between informal and formal areas of Ouagadougou, a sub-Saharan African city

BACKGROUND Countries of sub-Saharan Africa are increasingly confronted with hypertension and urbanization is considered to favor its emergence. This study aims to assess the difference in the prevalence of hypertension between formal and informal urban areas of Ouagadougou and to determine the risk factors associated with hypertension in these urban populations of sub-Saharan Africa. METHODS A cross-sectional survey was conducted in 2010 on 2041 adults aged 18 years and older in formal and informal areas of Ouagadougou. Data was collected through personal interviews conducted at home. Blood pressure and anthropometric measurements were taken by trained interviewers. Logistic regressions were fitted to identify factors associated with hypertension. RESULTS The overall prevalence of hypertension was 18.6% (95% confidence interval [CI], 16.9-20.3) and its detection was 27.4% (95% CI, 22.9-31.9). Prevalence of hypertension in formal settings was 21.4% (95% CI, 19.0-23.8), significantly higher than prevalence in informal settings: 15.3% (95% CI, 13.0-17.6). However, this difference disappeared after adjusting for age. In addition to age, being an unmarried woman (odds ratio [OR] = 1.7; 95% CI, 1.1-2.4), recent rural-to-urban migration (OR = 1.8; 95% CI, 1.2-2.8), obesity (OR = 1.8; 95% CI, 1.1-3.1) and physical inactivity (OR = 1.9; 95% CI, 1.2-3.0), were independent risk factors for hypertension. CONCLUSIONS Hypertension is common among the adult population of Ouagadougou but its detection is low. While there are no differences between formal and informal areas of the city, rural-to-urban migration emerges as an independent risk factor. Known risk factors as obesity and physical inactivity are confirmed while the vulnerability of unmarried women and rural-to-urban migrants maybe specific to this west African population.