Long-term association of ambient air pollution and hypertension in adults and in children: A systematic review and meta-analysis

The association of long-term ambient air pollution and hypertension has been inconsistently reported. We performed an updated systematic review and meta-analysis to assess the association between long-term exposure to ambient air pollution and risk of hypertension in adults and in children. PubMed, EMBASE, and Web of Science were searched up to August 7, 2020 for published articles examining the association of long-term exposure to ambient air pollution, including particulate matter (PM; ultrafine particles, PM1, PM1–2.5, PM2.5, PM2.5–10 and PM10), nitrogen dioxide (NO2), nitrogen oxides (NOx), sulfur dioxide (SO2), ozone (O3), carbon monoxide (CO) and hypertension. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) for hypertension with each 10-μg/m3 increase in air pollutants were calculated by random-effects models. We included 57 studies (53 of adults and 4 of children) in the meta-analysis. Risk of hypertension was significantly increased in adults with each 10-μg/m3 increase in exposure to PM2.5 (OR 1.10, 95% CI 1.07–1.14; I2 = 93.1%; n = 37), PM10 (1.04, 1.02–1.07; I2 = 44.8%; n = 22), and SO2 (1.21, 1.08–1.36; I2 = 96.6%; n = 3). Hypertension was not significantly associated with PM1 (n = 2), PM2.5–10 (n = 16), NO2 (n = 27), or NOx (n = 17). In children, the summary ORs (95% CIs) for each 10-μg/m3 increase in PM2.5, PM10, SO2 and O3 were 2.82 (0.51–15.68; I2 = 83.8%; n = 2), 1.15 (1.01–1.32; I2 = 0; n = 2), 8.57 (0.13–575.58; I2 = 94.2%; n = 2), and 1.26 (0.81–1.09, I2 = 91.6%; n = 2), respectively. Long-term ambient air pollution is a potential risk factor for hypertension in adults. More studies are needed to explore the effects of long-term air pollution on hypertension in children.