Impact of Ambient Air Pollution on Cardiovascular Diseases in Low- and Lower-Middle-Income Countries: A Systematic Review and Meta-Analysis

Air pollution contributes to over 8.1 million deaths annually, predominantly from cardiovascular causes. The burden of air pollution is significantly higher in low-income countries (LICs) and lower middle-income countries (LMICs), yet most air pollution research is performed in higher-income countries. Our objective was to systematically review the association between exposure to ambient air pollution and cardiovascular disease (CVD) in LICs and LMICs. PubMed and Global Health databases were systematically searched for studies that explore associations between daily increases in gaseous (SO₂, NO₂, CO, O₃) and particulate matter (PM) air pollutants with CVD mortality and hospital admission in adults. Studies were assessed for risk of bias based on outcome validity, exposure measurement quality, and confounder adjustment. A random-effects model was used to estimate overall and per-pollutant risks from short-term exposure studies, standardised to 10 μg/m³ increments. Of 1329 articles screened, 48 met the inclusion criteria, of which 22 included a measure of relative risk suitable for meta-analysis. Short-term exposure to PM₂.₅.and PM₁₀. were associated with increased combined mortality and hospital admission with 0.53% (95% CI: 0.31%-0.75%) and 1.68% (95% CI: 0.17%-3.21%) increase per 10 μg/m³, respectively. NO₂ showed a 0.66% increase (95% CI: 0.36%-0.97%) per 10 μg/m³. This systematic review highlights the limited evidence on air pollution and CVD in LICs and LMICs. Nonetheless, this meta-analysis found positive associations between several ambient air pollutants and cardiovascular hospital admissions and mortality. There is the vital need for further research in underrepresented regions, particularly on the effects of long-term exposure, in order to establish the true burden of air pollution on cardiovascular health in regions where air pollution is frequently high, or access to healthcare is limited.