Association between built environment and sleep duration mediated by air pollution: a cohort study in China

The joint effects of complex built environment exposures on sleep duration and their underlying mechanisms remain unclear. This study aimed to evaluate the overall effects of residential built environment mixtures on longitudinal changes in sleep duration, and to explore potential mediation through air pollution.

We analyzed data from 18,891 adults in Yinzhou cohort in China, with baseline (2015-2017) and follow-up (2021-2023) assessments. Sleep duration was self-reported via questionnaires. Linear mixed models and quantile g-computation were employed to evaluate the associations between built environment mixture (green and blue space, light at night [LAN], walkability, road proximity, and population density) and longitudinal change of sleep duration. Structural equation modeling was utilized to assess mediation by air pollutants (PM₁₀, PM_2.5, and NO₂).

Each quartile increase in the built environment mixture index was associated with a 0.057 h/year (95%CI: 0.039, 0.075) increase in sleep duration. Walkability (37.4%), green space (28.4%), and blue space (26.5%) drove the protective effects, whereas population density (63.3%) and LAN (36.7%) contributed negatively. Furthermore, interquartile range (IQR) increases in PM₁₀, PM_2.5, and NO₂ were significantly associated with shorter sleep duration (β=-0.027 h, -0.048 h, and - 0.071 h, respectively). Air pollutants partially mediated the associations, with mediation proportions varying across exposures; notably, lower NO₂ and PM_2.5 explained up to 45.3% and 21.5% of the protective effects of walkability and green space on sleep duration, respectively.

Built environment features were significantly associated with sleep duration changes, partially through air pollution. Optimizing urban planning while mitigating air pollution may support sleep health.