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

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 PM_2.5 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, PM_2.5, PM₁₀) and major chemical constituents of PM_2.5 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 PM_2.5 chemical constituents on sleep. An interquartile range (IQR) increase in PM₁, PM_2.5, 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 PM_2.5 constituents correlated with reduced nighttime sleep duration, with SO₄^2- being a major contributor. Regardless of particle size and PM_2.5 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 PM_2.5 constituent SO₄^2- appears to be the major contributor to these associations.