High night-to-night variability in ambient temperature is associated with increased sleep timing irregularity

Daily temperature variability is projected to increase in some world regions up to 100% by 2100. This study investigated associations between night-to-night temperature variability with sleep duration timing and regularity.

Data were collected from global users of the Withings Sleep Analyzer (n = 125,295) and ScanWatch (n = 238,550) between January 2020-September 2023. Sleep regularity was assessed using intra-monthly variation in sleep duration and timing (onset, midpoint and offset). Ambient temperature data were extracted from established climate models to calculate night-to-night temperature variability. Fixed-effects models were used to assess the association between night-to-night temperature variability and sleep regularity (duration and timing).

Participants (n = 313,822) were middle-aged (50 ± 15 years), 70% male, with an average 17 months of data. During months with high vs. low night-to-night temperature variability (99th percentile: 4.3°C vs. 50th percentile: 1.9°C), sleep onset variability was higher in southern (mean [95%CI]; 17.9 [16.1, 19.6]min), central (6.5°C vs. 1.0°C; 32.2 [29.8, 34.6]min) and northern locations (5.5°C vs. 2.1°C; 11.4 [11.2, 11.7]min). There was greater variability in sleep midpoint and offset with higher night-to-night temperature variability, with similar effect sizes. High night-to-night temperature variability was associated with <10 minutes difference in sleep duration irregularity.

Our findings highlight that high night-to-night temperature variability is associated with a 20%-50% increase in sleep timing irregularity, with central and southern regions being more affected. Given that sleep irregularity is associated with adverse health outcomes, targeted interventions to mitigate the impact of temperature variability on sleep health is an important public health priority.