How do we sleep while our beds are burning? High ambient temperatures are associated with substantial sleep loss.

Abstract

Study objectives: High ambient temperatures are associated with negative health outcomes, including heat stress, injuries and accidents, and poor mental health. Sleep loss may contribute to these adverse impacts. However, robust supporting evidence is lacking.

Methods: Data from a global sample of sleep tracker users (N = 317 758; Withings Sleep Analyzer [WSA]: n = 116 879; Withings ScanWatch: n = 200 879) between January 2020 and September 2023 (~165 million nights) were analyzed. Ambient temperatures (24 hour average) were extracted from a climate model for each nightly observation based on the users' location. We used the case-time-series design with participant-year-week intercept and spline functions to derive exposure-response curves between temperature and short sleep (<6 hours/night) prevalence, adjusting for other time-varying factors and meteorological variables.

Results: High temperatures (99th vs 50th percentile of the observed global distribution; 27.3°C vs 12.2°C) were associated with (mean [95%CI]) -15.2 [-15.6, -14.9] and -16.9 [-17.4, -16.4] minute sleep loss in the users of the smartwatch and under-mattress sensors, respectively. Similarly, high temperatures were associated with an approximately 40% relative increase in the probability of short sleep on the same night (WSA: Risk Ratio: RR [95%CI]; 1.40 [1.38, 1.41]; ScanWatch: 1.43 [1.41, 1.44]). Estimates ranged between 10% and 75% depending on the country. Sleep loss to high temperatures was higher in participants residing in Europe and countries with lower national gross domestic product per capita.

Conclusions: High temperatures negatively impact sleep duration and increase the probability of short sleep globally. Our findings suggest that rising temperatures may increase the health impacts of short sleep. Statement of Significance High ambient temperatures are linked to negative health outcomes, with sleep loss potentially contributing to these effects. This study analyzed data from 317 758 global sleep tracker users to examine the relationship between temperature and short sleep. Results showed an approximately 40% relative increase in the probability of short sleep at high temperatures (99th vs 50th percentile; 27.3°C vs 12.2°C) globally. Sleep loss to high temperatures was higher in participants residing in countries with lower national gross domestic product per capita and older adults. These results suggest that sleep inadequacy from rising temperature due to climate change may further amplify global inequalities. Our findings also highlight the urgent need for targeted strategies to mitigate temperature-induced sleep loss.