Nighttime temperature and sleep duration in the Chinese population

Background Ambient temperature influences sleep by modulating circadian thermoregulation. However, limited evidence exists regarding how extreme nighttime temperatures affect sleep in Chinese real-world settings. Methods We collected 1,245,817 sleep records from 7,682 participants between 2017 and 2019 using wearable devices. Hourly temperature data were obtained from the land component of the fifth generation of European Re-Analysis. We employed mixed-effects models to assess the impact of extreme hot nighttime temperatures during the hot season and extreme cold nighttime temperatures during the cold season on sleep. We applied a distributed lag non-linear model to adjust for lagged effects of daytime temperature. Subgroup analyses were conducted to identify susceptible populations. Results During the hot season, a 5°C increase in hot night excess was associated with a 0.81-minute reduction in total sleep duration (95% CI: -1.32, -0.31), primarily driven by a decrease in light sleep (-0.77, 95% CI: -1.22, -0.31). Conversely, during the cold season, a 5°C decrease in cold night excess was linked to a 0.81-minute increase in total sleep (95% CI: 0.05, 1.17), with both light sleep (0.44, 95% CI: 0.12, 0.76) and deep sleep (0.35, 95% CI: 0.17, 0.53). These effects generally remained consistent after adjusting for the lagged effects of daytime temperatures. Elderly and obese individuals were more vulnerable to heat-related sleep disruptions. Conclusions This study highlights the potential impact of climate change-induced nighttime warming on sleep and underscores the importance of optimizing thermal environments, particularly for the elderly and obese individuals, to enhance sleep duration during the hot season.