Exposure to high temperature and sleep in preadolescents from two European birth cohorts

Introduction: Hot temperatures disrupt sleep in adults, but the impact on younger populations, despite the essential role of sleep in their health and development, remain underexplored. Aim: We assessed the relationship between ambient nocturnal temperature and physiological sleep characteristics and self-reported daytime sleepiness in preadolescents from two European birth cohorts. Methods: We evaluated preadolescents from the Dutch Generation R Study (3,340 (mean age 13.5 years) and the Spanish INMA Project (587 (mean age 14.3 years)). Ambient nocturnal temperature at participants’ residences was estimated with the UrbClim model at a 100x100m resolution. Physiological sleep characteristics (total sleep time, sleep onset latency, wake after sleep onset, sleep efficiency) were measured with a wrist-accelerometer up to nine nights. Self-reported daytime sleepiness was assessed using the Paediatric Daytime Sleepiness Scale or the Sleep Disturbances Scale for Children. We ran linear mixed models for each physiological sleep characteristic and distributed lag models for daytime sleepiness. Results: Nocturnal temperatures ranged from −7.0–31.0 °C (Generation R) and 1.3–30.3 °C (INMA). In Generation R, higher nocturnal temperatures were associated with a shorter total sleep time (−3.7 min per 5 °C [95 % CI −5.4; −1.9]) and poorer sleep efficiency (−0.3 % per 5 °C [95 % CI −0.5; −0.1]), especially in warmer months and low socioeconomic status level neighbourhoods. No associations were found for physiological sleep characteristics in INMA or for daytime sleepiness scores in either cohort. Conclusion: Warmer temperatures were associated with shortened sleep duration and poorer sleep efficiency in adolescents in the Netherlands, but not in Spain. These results suggest potential cross-country differences in the relationship between ambient temperature and adolescent sleep, though comparisons should be made cautiously due to differences in climate, acclimatization, population characteristics, and sample size. Climate change may worsen preadolescents sleep, underscoring the need for strategies to protect sleep and promote long-term health.