Bedroom Temperature

Research summary

• Sleep onset and maintenance are physiologically coupled to a decline in core body temperature and a rise in distal (hand/foot) skin temperature, a mechanism laid out in detail across several reviews of sleep thermoregulation and linked to insomnia, restless legs syndrome, and other sleep disorders when disrupted.
• Real-world monitoring data point to a fairly consistent optimal range: a longitudinal wearable-sensor study of community-dwelling older adults found sleep was most efficient between roughly 20-25°C, with a clinically meaningful 5-10% drop in sleep efficiency as bedroom temperature rose from 25°C to 30°C, and a study of children found a similar curvilinear pattern in which both overly hot and overly cold bedrooms degraded sleep, with lower-income families more likely to experience extreme bedroom temperatures.
• Two systematic reviews converge on the same conclusion from a climate-change angle: rising ambient and indoor temperatures are consistently associated with worse sleep quality and quantity globally, concentrated in the hottest months and among the most vulnerable populations.
• On the intervention side, a meta-analysis of randomized trials found that passive body heating via a warm bath or shower 1-2 hours before bed measurably shortens sleep onset latency and improves sleep efficiency, plausibly by amplifying the same distal skin-warming, heat-dissipation mechanism, and a small randomized trial confirmed a related periocular-warming manipulation accelerates sleep onset.
• The underlying mechanism and observational associations are well established, but large randomized trials directly manipulating ambient bedroom temperature itself remain sparse.