Joint associations of air pollutants during pregnancy, infancy, and childhood with childhood persistent asthma: Nationwide database study in Japan

Abstract

The joint effect of air pollutants at relatively low levels requires further investigation. Here, a database study was performed to evaluate the effects of exposure to mixtures of air pollutants during pregnancy, infancy, and childhood on childhood persistent asthma. We used the Japan Medical Data Center database, which provides access to family linkages and healthcare provider addresses, and included child-mother dyads in which the child was born between January 2010 and January 2017. The exposure of interest was ground-level air pollutants, and the primary outcome was childhood persistent asthma at 45 years of age, as defined based on outpatient and inpatient asthma disease codes and/or asthma medication dispensing claims. The weighted quantile sum (WQS) regression was used to evaluate the effects of air pollutant mixtures on 52,526 child-mother dyads from 1149 of 1907 municipalities (60.3 %) in Japan. The WQS regression models showed that with every 10th percentile increase in the WQS index, ground-level air pollutants during pregnancy, infancy, and childhood increased the risk of childhood persistent asthma by an odds ratio of 1.04 (95 % CI: 1.02-1.05; p<0.001), 1.02 (95 % CI: 1.01-1.03; p<0.001), and 1.03 (95 % CI: 1.01-1.04; p<0.001), respectively. Moreover, particulate matter with an aerodynamic diameter ≤ 2.5 µm was assigned the highest weight across all three exposure periods. Relatively high weights were assigned to suspended particulate matter and photochemical oxidants during pregnancy, carbon monoxide during infancy, and photochemical oxidants during childhood. Our study showed that a mixture of low-level air pollutants has a detrimental association with childhood persistent asthma.

Keywords: Air pollution; Asthma; Childhood asthma; Mixture; Ozone; PM(2.5).