Abstract
OBJECTIVE: Sleep is a crucial behavioral determinant of physical and psychological well-being. With the rapid urbanization of China, noise pollution has become a growing concern, and its impact on sleep has raised substantial public health attention. This study aims to investigate the potential non-linear relationship between environmental noise and individual sleep duration, and the moderating roles of urban green space and city size. METHODS: We conducted a longitudinal analysis using data from the China Health and Retirement Longitudinal Study. City-level noise exposure was quantified using the Baidu Noise Index, a novel approach in this context. Data on urban population and green space coverage were obtained from the National Bureau of Statistics of China. Fixed-effects regression models were employed to estimate the impact of noise on sleep duration, and moderation analysis was applied to explore the roles of green space and city size. RESULTS: An inverted U-shaped association was observed between noise levels and sleep duration (linear β = 0.746, P < 0.001; quadratic β = -0.955, P < 0.001), with an inflection point at 0.391 [95% confidence interval (CI): [0.320, 0.566]]. Moreover, this inverted U-shaped pattern was attenuated in cities with higher green space coverage (quadratic interaction β = 0.822, P < 0.05) and larger population (quadratic interaction β = 1.072, P < 0.001). CONCLUSION: This study underscores the multifaceted relationship between noise exposure and sleep duration, providing a theoretical foundation for urban planning and health policy formulation, particularly in optimizing urban sound environments and promoting green space development.