Short-term and Intermediate-term Fine Particulate Air Pollution are Synergistically Associated with Habitual Sleep Variability in Adolescents

Abstract

BACKGROUND AND AIM: While both fine particulate (PM2.5) exposure and high sleep variability are potential risk factors for cardiovascular diseases (CVD), the association between PM2.5 and sleep variability remains unclear. Our study aimed at investigating the association between PM2.5 exposure and habitual sleep variability (HSV) in a population-based sample of U.S. adolescents. METHODS: Data obtained from 421 adolescents, who participated in the Penn State Child Cohort follow-up examination, were analyzed. For each participant, we collected 24-hour (i.e. short-term) individual-level PM2.5 exposure by using a personal nephelometer. We further estimated their residential-level PM2.5, during the 60-day period prior to the examination (i.e. intermediate-term), by utilizing a GIS-based kriging approach. Actigraphy was used to collect participants’ total sleep time (TST) for 7 consecutive nights. HSV was calculated as the standard deviation (SD) of the 7-night TST. Multivariable-adjusted linear regression was used to assess the association between PM2.5 exposures and HSV. An interaction between the short- and intermediate-term PM2.5 was created to test their potential synergistic impact on HSV. RESULTS:Both short-term and intermediate-term PM2.5 exposure were significantly (both p0.01) associated with HSV. There was a marginally significant (p=0.08) synergistic interaction between short-term and intermediate-term PM2.5. Specifically, the association between intermediate-term PM2.5 and HSV became stronger as short-term PM2.5 increased, and vice versa. For example, the regression coefficients (SE) between 1 SD (2.2 µg/m3) increase in intermediate-term PM2.5 and HSV were 3.5 (2.7, p=0.21), 5.1 (2.3, p=0.03), and 10.5 (3.4, p0.01) minutes, when short-term PM2.5 were at its 10th percentile (1.7 µg/m3), median (9.7 µg/m3), and 90th percentile (35.3 µg/m3), respectively. CONCLUSIONS:Both short-term and intermediate-term PM2.5 exposure were associated with higher sleep variability among adolescents. More importantly, short-term and intermediate-term PM2.5 exposure may impact sleep variability in a synergistic manner, which highlighted the importance of PM2.5 reduction in the early prevention of CVD. KEYWORDS: Particulate Matter, Sleep Variability, Adolescents