Impact of short- and long-term exposure to air pollution on blood pressure: A two-decade population-based study in Tehran.

Plenty of recent studies on the impact of air pollution on blood pressure (BP) exist; however, there is a lack of data for the highly polluted Eastern Mediterranean region. We evaluated the associations of short-term exposure to air pollutants with systolic BP (SBP) and diastolic BP (DBP) and the long-term impact of air pollutants on incident hypertension, among Tehranian adults. In the Tehran Lipid and Glucose Study, 4580 nonhypertensive participants aged 20-69 years (41.6% male) were followed from 2001 to 2018 through 3-year follow-ups and 4-5 examinations of them were recorded. The air pollutants included particulate matter with a diameter ≤10 μm (PM), carbon monoxide (CO), ozone (O), nitrogen dioxide (NO), and sulfur dioxide (SO). The mixed-effects transition model estimated the air pollution impact on BP. The proportional hazards Weibull model measured the long-term effects of air pollutants on the multivariate hazard of incident hypertension. The air pollutants were put in the models in the form of mean annual level, applying three versions of 1, 2, and 3 years before the follow-ups. During a median follow-up of 12.3 years, 1618 cases of hypertension were found. In the short-term, increase in CO did not affect SBP but decreased DBP with a delay effect lasting for 14 days; increase in NO raised SBP with a 14-day lag, however did not change DBP; increase in O reduced SBP with a 14-day lag but made slight non-significant increase in DBP; rise in PM concentrations led to increased SBP (lag 0-3 days) and DBP with lags of 0-3 days and 12-14 days and increase in SO made the largest increases in DBP with lags lasting for 14 days, but did not affect SBP. Regarding incident hypertension in the long-term, the increase in CO had no significant effect; increase in NO decreased the risk over the 2- and 3-year time spans; rise in O, PM, and SO levels increased the risk in all time spans; the largest hazard ratio [1.96 (95% CI: 1.48, 2.62)] for incident hypertension was attributable to PM in 3 years. Considering the major effects of air pollutants including O, SO, and especially PM on incident hypertension, urgent public health policies should be implemented to reduce the burden of air pollution in metropolitan city of Tehran.