Associations of outdoor fine particulate air pollution and cardiovascular disease in 157 436 individuals from 21 high-income, middle-income, and low-income countries (PURE): a prospective cohort study

Abstract

Background Most studies of long-term exposure to outdoor fine particulate matter (PM2-5) and cardiovascular disease are from high-income countries with relatively low PM2-5 concentrations. It is unclear whether risks are similar in low-income and middle-income countries (LMICs) and how outdoor PM2-5 contributes to the global burden of cardiovascular disease. In our analysis of the Prospective Urban and Rural Epidemiology (PURE) study, we aimed to investigate the association between long-term exposure to PM2-5 concentrations and cardiovascular disease in a large cohort of adults from 21 high-income, middle-income, and low-income countries. Methods In this multinational, prospective cohort study, we studied 157 436 adults aged 35-70 years who were enrolled in the PURE study in countries with ambient PM2-5 estimates, for whom follow-up data were available. Cox proportional hazard frailty models were used to estimate the associations between long-term mean community outdoor PM2-5 concentrations and cardiovascular disease events (fatal and non-fatal), cardiovascular disease mortality, and other non-accidental mortality. Findings Between Jan 1, 2003, and July 14, 2018, 157436 adults from 747 communities in 21 high-income, middleincome, and low-income countries were enrolled and followed up, of whom 140020 participants resided in LMICs. During a median follow-up period of 9-3 years (IQR 7-8-10-8; corresponding to 1-4 million person-years), we documented 9996 non-accidental deaths, of which 3219 were attributed to cardiovascular disease. 9152 (5-8%) of 157436 participants had cardiovascular disease events (fatal and non-fatal incident cardiovascular disease), including 4083 myocardial infarctions and 4139 strokes. Mean 3-year PM2-5 at cohort baseline was 47-5 µg/m³ (range 6-140). In models adjusted for individual, household, and geographical factors, a 10 µg/m³ increase in PM2-5 was associated with increased risk for cardiovascular disease events (hazard ratio 1-05 [95% CI 1-03-1-07]), myocardial infarction (1-03 [1-00-1-05]), stroke (1-07 [1-04-1-10]), and cardiovascular disease mortality (1-03 [1-00-1-05]). Results were similar for LMICs and communities with high PM2-5 concentrations (>35 µg/m³). The population attributable fraction for PM2-5 in the PURE cohort was 13-9% (95% CI 8-8-18-6) for cardiovascular disease events, 8-4% (0-0-15-4) for myocardial infarction, 19-6% (13-0-25-8) for stroke, and 8-3% (0-0-15-2) for cardiovascular disease mortality. We identified no consistent associations between PM2-5 and risk for non-cardiovascular disease deaths. Interpretation Long-term outdoor PM2-5 concentrations were associated with increased risks of cardiovascular disease in adults aged 35-70 years. Air pollution is an important global risk factor for cardiovascular disease and a need exists to reduce air pollution concentrations, especially in LMICs, where air pollution levels are highest