# Association of long-term exposure to air pollution with sleep among middle-aged and older adults in China: A nationwide study from 2015 to 2018

## TL;DR

Long-term exposure to air pollution in China is linked to worse sleep duration and quality in middle-aged and older adults.

## Contribution

This nationwide study identifies specific air pollutants and their temporal exposure patterns affecting sleep outcomes in older Chinese adults.

## Key findings

- CO exposure was most strongly linked to reduced sleep duration.
- NO2 exposure was most strongly associated with sleep quality deterioration.
- Urban residents experienced more significant sleep quality impacts from pollution.

## Abstract

This study aims to evaluate the associations of long-term exposure to five major air pollutants (PM2.5, PM10, NO2, SO2, and CO) with sleep duration and quality among middle-aged and older Chinese adults.

This study used data from 14856 adults aged 45 and above participating in the China Health and Retirement Longitudinal Study (CHARLS). Changes in nocturnal sleep duration between baseline (2015) and follow-up (2018) were categorized into three groups: reductions ≥1 h, 1.5 h, or 2 h. The increase in the number of days with restless sleep at follow-up was defined as a deterioration in sleep quality. We used the STET model to estimate air pollution exposure and calculate the concentration differences over 1- or 2-year periods preceding each interview. We investigated the associations of exposure differences to five pollutants with sleep duration and quality through generalized linear mixed and ordinal logistic regression models. Interaction analyses were employed to identify potential effect modifiers.

All 1-year exposure differences to air pollution positively correlated with reductions in sleep duration of both ≥1.5 h and ≥2 h. CO exposure demonstrated the highest risk for a ≥ 1.5 h reduction (OR = 1.451; 95% CI: 1.065–1.975) and a ≥ 2 h reduction (OR = 1.557; 95% CI: 1.135–2.135) per 1 μg/m3 increment. Higher exposure levels to PM2.5, PM10, NO2 and SO2 correlated with elevated risks of sleep quality deterioration. NO2 exposure demonstrated the highest risk, with a 22.3% higher risk per 10 μg/m3 increment (95% CI: 1.039–1.439). Pollutants affected sleep duration and quality in varying temporal patterns. Overall, 1-year exposure difference considerably impacted the sleep duration, while 2-year exposure difference significantly impacted the sleep quality. We also found that the air pollution’s adverse impacts on sleep quality were especially significant for those living in urban areas.

Long-term exposure to air pollution is associated with adverse sleep outcomes in middle-aged and older populations.