Early-Life Exposure to Particulate Matter and Sleep in Chinese Toddlers: The Roles of Particle Size and Particulate Constituents.

The impact of particulate matter (PM) on pediatric sleep has been documented, yet the roles of particle size and particulate constituents remain poorly understood. This study aims to evaluate the associations between early-life exposure to different sizes of PM and specific chemical constituents of PM2.5 and sleep in toddlers. In this birth cohort in Guangzhou, China, 514 mother-child pairs with follow-ups at age two between 2017 and 2018 were eligible for participation. Using high-resolution ground-level grid data, we estimated PM exposure (PM1, PM2.5, PM10) and major chemical constituents of PM2.5 during the early-life period. The sleep of two-year-old toddlers was assessed using the Chinese version of the Brief Infant Sleep Questionnaire. We used multivariable linear and logistic regression models to analyze the associations between PM exposure and sleep. Quantile g-computation was applied to assess the joint exposure effects of PM2.5 chemical constituents on sleep. An interquartile range (IQR) increase in PM1, PM2.5, and PM10 exposure during early life was associated with reduced nighttime sleep duration (β = -0.18; 95%CI: -0.32, -0.04; β = -0.23; 95%CI: -0.38, -0.08; β = -0.21; 95%CI: -0.35, -0.07). Combined early-life exposure to PM2.5 constituents correlated with reduced nighttime sleep duration, with SO42- being a major contributor. Regardless of particle size and PM2.5 constituents, we identified consistent findings during pregnancy. We found positive associations between prenatal PM exposure and reduced nighttime sleep in two-year-old toddlers. The PM2.5 constituent SO42- appears to be the major contributor to these associations.