Effects of ambient air pollutants and environmental greenness on the incidence of pre-/hypertension in children and adolescents

Abstract

Introduction Ambient air pollution and environmental greenness have been suggested to influence the risk of hypertension (1,2). This study aims to estimate the long-term effects of air pollution and greenness on the incidence of pre-/hypertension during the early life course considering different hypothetical intervention scenarios. Methods Our study includes 2385 children and adolescents aged 2-9 years at baseline who participated in three examination waves (2007/08, 2009/10, 2013/14) of the European IDEFICS/I.Family study (3). Ambient annual average exposure to particulate matter <2.5 μm (PM2.5), black carbon (BC) and nitrogen dioxide (NO2) at the place of residence was estimated by land use regression models; environmental greenness was assessed using the Normalized Difference Vegetation Index (NDVI). Applying g-computation, we estimated the effects of (i) sustained percentual changes (e.g. 10% decrease of air pollutants/increase of NDVI) as well as (ii) adherence to defined standard levels over a 6-year period on the combined incidence of pre-hypertension and hypertension as compared to no intervention. Models were adjusted for socio-demographics, behavioral factors and temperature. Results The 6-year risk of developing pre-/hypertension under no intervention was 14.4%. We found a clear dose-dependent relationship showing higher risk reductions when (i) imposing larger percentual reductions as well as (ii) when imposing lower hypothetical standards for the air pollutants. The largest effects were observed for PM2.5, e.g. when reducing PM2.5 to comply with a standard of ≤10 μg/m3, the risk of developing pre-/hypertension was lowered by -10.7 [-14.1, -5.7; 95% bootstrap confidence interval] percentage points as compared to no intervention. Effects of BC reductions were less strong, e.g. -5.3 [-10.2, 1.7] when reducing BC to ≤0.8x10-5/m and only small (non-significant) effects were found for interventions on NO2. Hypothetically increasing the NDVI by 10% and 20% lowered the pre-/hypertension risk by -2.4 [-4.9, 2.7] and -4.2 [-8.6, 12.1] percentage points, respectively. Sensitivity analyses suggested effects of air pollution mainly on systolic (SBP) but not diastolic blood pressure. Conclusions/Outlook Our study provides evidence that reductions in PM2.5 and BC can lower the incidence of pre-/hypertension via SBP reduction in children and adolescents. Increasing environmental greenness may also slightly lower the risk of developing pre-/hypertension. Our findings may motivate policymakers to ensure adherence to recommended levels of air pollutants and foster environmental greenness.