Climate, Air Quality and Their Contribution to Cardiovascular Disease Morbidity and Mortality in Low- and Middle-Income Countries: A Systematic Review and Meta-Analysis.

Background: Increasing exposure to climatic features is strongly linked to various adverse health outcomes and mortality. While the link between these features and cardiovascular outcomes is well established, most studies are from high-income countries.

Objectives: This review synthesizes evidence as well as research gaps on the relationship between climate indicators, household/ambient air pollution, and all-cause cardiovascular disease (CVD) morbidity and mortality in low- and middle-income countries (LMICs).

Methods: Seven electronic databases were searched up to June 15, 2024. Articles were included if they focused on LMICs, addressed all-cause CVD morbidity and/or mortality, and studied climate or environmental exposures. Studies were selected using ASReview LAB, extracted and analyzed with random effect meta-analysis performed if sufficient articles were identified.

Results & conclusion: Out of 7,306 articles, 58 met the inclusion criteria: 26 on morbidity, 29 on mortality, and 3 on both. Exposures included PM₁₀, PM_2.5, NO₂, SO₂, BC, O₃, CO, solid fuel usage, and temperature variation. Short-term exposure to PM_2.5 was significantly associated with CVD morbidity (RR per 10 µg/m³ increase:1.006, 95% CI 1.003-1.009) and mortality (RR:1.007, 95% CI 1.002-1.012). Short-term exposure to NO₂ and O₃ also increased CVD mortality risk. Long-term exposure to PM_2.5 elevated CVD morbidity (RR per 10 µg/m³ increase:1.131, 95% CI 1.057-1.210) and mortality (RR:1.092, 95% CI 1.030-1.159). High and low temperatures and long-term solid fuel use were linked to CVD deaths. The bulk of studies were from mainland China (72%), which may not accurately reflect the situation in other LMICs. Sub-Saharan Africa was particularly lacking, representing a major research gap.