The Impact of Reducing Air Pollution during Pregnancy on Cognitive Abilities at Four Years of Age: The UGAAR Randomized Controlled Trial of HEPA Air Cleaners

Abstract

Background Air pollution is a leading contributor to the global burden of disease. Observational evidence indicates that exposure can affect cognitive abilities, but the influence of gestational exposure on cognitive development in childhood is poorly understood. The Ulaanbaatar Gestation and Air Pollution Research (UGAAR) study is a randomized controlled trial of portable (High-Efficiency Particulate Air) HEPA air cleaners use during pregnancy and childhood development. Ulaanbaatar, Mongolia’s capital, is among the most polluted cities due primarily from coal combustion for home heating. We investigated the effect of air cleaners use during pregnancy on cognitive development in 4-year old children. Methods We enrolled 540 non-smoking, apartment-dwelling pregnant women in 2014 and 2015 and randomly assigned them to an intervention (use of 1-2 HEPA air cleaners from enrollment to childbirth) or control (no air cleaners) group. There were 464 live births. We administered the Wechsler Preschool and Primary Scale of Intelligence, 4th edition (WPPSI) to 390 children (187 control and 203 intervention) at a mean age of 48.2 months. Our primary outcome was full-scale IQ. Results The mean maternal age at birth was 29 (26 - 33) years. We previously reported 29% reduction in particulate matter (PM) concentration. The intervention was associated with a 3.3 point (95% CI: 0.39, 6.25) increase in full-scale IQ. The mean verbal comprehension score was also higher (3.8 points, 95% CI: 0.5 - 7.1 points) among children in the intervention group. Intervention participants had higher mean scores across all 10 of the WPPSI indices, although confidence intervals spanned the null.Conclusion Our findings indicate that reducing PM exposure during pregnancy led to an improvement in children’s neurocognitive performance at four years of age. The use of portable air cleaners during pregnancy may mitigate some of the adverse neurodevelopmental impacts of air pollution.