Do the socioeconomic and hypertension gradients in rural populations of low- and middle-income countries differ by geographical region? A systematic review and meta-analysis.

BACKGROUND Of the 1 billion people with hypertension globally, two-thirds reside in low- and middle-income countries (LMICs). The risk of hypertension in LMICs is thought to be positively associated with socioeconomic status (SES). However, recent studies have provided data inconsistent with this concept. Thus, we assessed the association between SES and hypertension in rural populations of LMICs. Further, we explored whether this association differs according to geographical region. METHODS Through a search of databases we identified population-based studies that presented risk estimates for the association between SES, or any of its proxies, and hypertension. Meta-analyses were conducted using a random effects model. RESULTS Overall, no association was detected between educational status and hypertension, whereas a positive association was observed with income. Interestingly, educational status was inversely associated with hypertension in East Asia {effect size [ES] 0.82 [95% confidence interval (CI) 0.78, 0.87]} but positively associated in South Asia [ES 1.28 (95% CI 1.14, 1.43)]. Higher income, household assets or social class were positively associated with hypertension in South Asia whereas no association was detected in East Asia and Africa. Compared with other occupations, farmers or manual labourers were associated with a lower risk for hypertension. Further, in regions such as Latin America, few studies were identified that fulfilled our inclusion criteria. CONCLUSIONS We provide evidence that the association between hypertension and SES in rural populations of LMICs in Asia varies according to geographical region. This has important implications for targeting intervention strategies aimed at high-risk populations in different geographical regions.