Effects of air pollution and residential greenness on sleep disorder: A 8-year nationwide cohort study

Sleep disorder influencing the quality of life, however, its contributing factors have not been fully identified yet. Recently the potential effects of environmental exposures like air pollution and greenness on sleep disorder have attracted attention, but the evidence in China is limited, particularly in the middle-aged and elderly. We conducted a nationwide prospective study that included 21,878 Chinese citizens aged 45 years or above. For each participant, the 3-year averaged exposure concentrations of air pollutants (including PM10, PM2.5, PM1, NO2) and greenness (assessed by NDVI) were estimated based on residential address. We used mixed-effects logistic models to examine the associations of sustained air pollutants and greenness exposures with the occurrence of sleep disorder, and used linear mixed-effects models to assess the associations with sleep duration. Specifically, interaction effects models were employed to identify potential modificators of the above associations. A total of 39,580 survey responses were received, with the overall occurrence rate of sleep disorder was 25.7%. A 10 μg/m3 increment in PM10 and PM2.5 were associated with increased occurrence of sleep disorder at 2% (aOR = 1.02, 95%CI:1.01, 1.04) and 7% (aOR = 1.07, 95%CI: 1.04, 1.11), and were associated with reduced sleep duration by 0.07 (95% CI: 0.08, 0.05) and 0.04 (95% CI: 0.05, 0.03) hours, respectively. Residential greenness appears to the potential protective factor for sleep disorder, that a 0.1 higher of the NDVI was associated a 9% (aOR = 0.91, 95%CI: 0.86, 0.96) decreased occurrence of sleep disorder and 0.09 h (95% CI: 0.05, 0.13) longer of sleep duration. Age and residence were identified as modificators of the above significant associations. Sustained exposure to air pollutants can increase the occurrence of sleep disorder and can reduce sleep duration, while exposure to higher levels of greenness can protect sleep health from the side effects of air pollutants.