Application of disease mapping to a global public health issue in low- and middle-income countries : a case study of hypertension

Background Hypertension is a global public health problem. It is the number one risk factor for mortality and the third leading cause of disability-adjusted life-years (DALYs) worldwide. The burden of the disease is more severe in low- and middle-income countries, where prevalence estimates are projected to increase by 30% over the next decade. This is not surprising owing to the on-going epidemiological transition taking place in these countries, where the interplay between social factors and disease is highly pertinent. However, evidence on the burden of hypertension and its determinants in low- and middle-income countries are limited. The overall aim of this research is to examine the prevalence and status of hypertension in low- and middle-income countries. The definition of hypertension used in this research is blood pressure measurement of ≥140 /90 mmHg (SBP/DBP), the use of antihypertensive medication, or self-reported physician diagnosis of hypertension. Objectives -To estimate the overall prevalence of hypertension in low- and middle-income countries. -To examine the socio-demographic determinants of hypertension in low- and middle-income settings. -To examine the geographic variation of hypertension prevalence in selected low-and middle-income countries. -To interpret the findings and discuss their implications for practice/policy and future research. Methods A systematic review and meta-analysis was conducted to provide overall and regional estimates of hypertension prevalence across low- and middle-income countries, and to examine patterns of the disease across different socio-demographic characteristics in these settings. Studies reporting hypertension prevalence in low- and middle-income countries were sought from electronic databases and grey literature. The data from these studies were analyzed using random-effects meta-analyses and sub-group analyses. Secondary data analyses of DHS datasets were also conducted to estimate hypertension prevalence and examine its geographic variation in selected low- and middle-income countries with hypertension data, while accounting for a number socio-demographic characteristics. The secondary data analyses entailed logistic regression and Bayesian geo-additive analyses. Odds ratios with 95% confidence intervals were reported for the logistic regression analyses, whereas posterior odds ratios with 95% credible intervals were reported for the Bayesian geo-additive analyses. Results The systematic review included 242 studies, comprising 1,494,609 adults from 45 countries. The overall prevalence of hypertension was 32.3% (95% confidence interval [CI] 29.4–35.3) with the Latin America and Caribbean region reporting the highest prevalence (39.1%, 95% CI 33.1–45.2). Prevalence was also highest in upper-middle income countries (37.8%, 95% CI 35.0–40.6) and lowest in low-income countries (23.1%, 95% CI 20.1–26.2). Prevalence among adults ≥65 years was substantially higher than adults <65 years; however, there was no significant sex-difference overall (31.9% vs 30.8%, p=0.6). Prevalence was generally higher among the non-educated compared to educated people (49.0% vs. 24.9%, p<0.05), among overweight/obese persons compared to normal weight (46.4% vs. 26.3%, p<0.05), and among urban settlers compared to rural (32.7% vs 25.2%, p=0.0005). Meta-regression showed that combined overweight/obesity (p<0.05) and being uneducated (p<0.05) significantly accounted for between-study heterogeneity in hypertension rates The secondary analysis comprised data on 93,247 respondents in 10 selected countries (Albania, Armenia, Azerbaijan, Ukraine, Uzbekistan, Egypt, Morocco, Lesotho, Senegal and Maldives). The prevalence of hypertension was lowest in Morocco (5.4%) and highest in Albania (22.7%). Age was the most consistent predictor of hypertension. Being employed was protective in the Eastern European countries (Albania, Armenia, Azerbaijan, Ukraine and Uzbekistan) (p<0.05 for each) and in African countries such as Egypt and Senegal (p<0.05 for each). Education was protective in Egypt, Senegal and Maldives (p<0.05 for each), but may be a strong determinant in Lesotho given the extremely high literacy rates in the country. Examining the geographic variation of hypertension revealed that Tirana and Elbasan districts had the highest burden of hypertension compared to other districts in Albania; Sharkia and Kalyoubia districts had the highest burden of hypertension compared to other districts in Egypt; while Quthing and Maseru districts had the highest burden of hypertension in Lesotho. Conclusion Overall, the findings provide contemporary and up-to-date estimates that reflect the significant burden of hypertension in low- and middle-income countries and evidence that hypertension remains a major public health issue in these settings. The findings also suggest that addressing the wider social determinants of hypertension, such as illiteracy and unemployment, may reduce overall prevalence of the disease in low- and middle-income countries.