Global prevalence and trends in hypertension and type 2 diabetes mellitus among slum residents: a systematic review and meta-analysis

OBJECTIVE: First, to obtain regional estimates of prevalence of hypertension and type 2 diabetes in urban slums; and second, to compare these with those in urban and rural areas. DESIGN: Systematic review and meta-analysis. ELIGIBILITY CRITERIA: Studies that reported hypertension prevalence using the definition of blood pressure ≥140/90 mm Hg and/or prevalence of type 2 diabetes. INFORMATION SOURCES: Ovid MEDLINE, Cochrane CENTRAL and EMBASE from inception to December 2020. RISK OF BIAS: Two authors extracted relevant data and assessed risk of bias independently using the Strengthening the Reporting of Observational Studies in Epidemiology guideline. SYNTHESIS OF RESULTS: We used random-effects meta-analyses to pool prevalence estimates. We examined time trends in the prevalence estimates using meta-regression regression models with the prevalence estimates as the outcome variable and the calendar year of the publication as the predictor. RESULTS: A total of 62 studies involving 108 110 participants met the inclusion criteria. Prevalence of hypertension and type 2 diabetes in slum populations ranged from 4.2% to 52.5% and 0.9% to 25.0%, respectively. In six studies presenting comparator data, all from the Indian subcontinent, slum residents were 35% more likely to be hypertensive than those living in comparator rural areas and 30% less likely to be hypertensive than those from comparator non-slum urban areas. LIMITATIONS OF EVIDENCE: Of the included studies, only few studies from India compared the slum prevalence estimates with those living in non-slum urban and rural areas; this limits the generalisability of the finding. INTERPRETATION: The burden of hypertension and type 2 diabetes varied widely between countries and regions and, to some degree, also within countries. PROSPERO REGISTRATION NUMBER: CRD42017077381.