Association between hypertension and dementia risk in low- and middle-income countries: A systematic review.

Background: Dementia prevalence is rising most rapidly in low- and middle-income countries (LMICs), yet most evidence on risk factors such as hypertension stems from high-income settings. In LMICs, hypertension may have a greater impact due to its high prevalence and poor control. We systematically reviewed evidence on the association between blood pressure and dementia and cognition in LMICs, and compared findings across regions.

Methods: We searched PubMed, Embase, PsycINFO, and Global Index Medicus and reviewed reference lists for relevant studies. We included longitudinal studies (follow-up ≥6 months) from LMICs on the association between systolic blood pressure or hypertension and incident dementia, mild cognitive impairment (MCI), or cognition, with a sample size of ≥500 individuals. Risk of bias was assessed using a modified Newcastle-Ottawa Scale.

Results: Of 8709 screened articles, 26 were included: 19 from Asia, six from Latin America, and one from Africa. Operationalization of hypertension and cognitive outcome was heterogeneous across studies, ranging from using routine care data to triple blood pressure measurements and comprehensive cognitive screening with expert review and validation. Follow-up duration ranged from 7 months to 16 years. Hypertension was associated with a higher risk of incident dementia (RR 1.26, 95 %CI 1.03 - 1.53) and MCI (RR 1.19, 95 %CI 1.09 - 1.29). Due to limited number of studies per region, we were unable to compare effect sizes across geographical regions.

Conclusion: Hypertension is associated with an increased risk of dementia and cognitive impairment in LMICs, but limited studies from Latin America and especially from Africa prevented reliable regional comparisons.