Too Hot To Sleep? Here’s Why

Bushfires are quite appropriately dominating our nation’s concerns during the current Australian heatwave. But for many, the struggle to sleep through soaring temperatures is a personal inferno that dominates conversation around offices and homes across the country. Sleep and body control of temperature (thermoregulation) are intimately connected. Core body temperature follows a 24-hour cycle linked with the sleep-wake rhythm. Body temperature decreases during the night-time sleep phase and rises during the wake phase. Sleep is most likely to occur when core temperature decreases, and much less likely to occur during the rises. Our hands and feet play a key role in facilitating sleep as they permit the heated blood from the central body to lose heat to the environment through the skin surface. The sleep hormone melatonin plays an important part of the complex loss of heat through the peripheral parts of the body. MORE: Heatwave: How To Cope With Australia’s Extreme Summer Temperatures At sleep onset, core body temperature falls but peripheral skin temperature rises. But temperature changes become more complex during sleep as our temperature self-regulation varies according to sleep stage. Research has shown how environmental heat can disturb this delicate balance between sleep and body temperature. An ambient temperature of 22˚ or 23˚ Celsius is ideal. Any major variation in this leads to disturbance of sleep with reduced slow wave sleep (a stage of sleep where the brain’s electrical wave activity slows and the brain “rests”), and also results in less dreaming sleep (rapid eye movement or REM sleep). Indeed during REM sleep, our ability to regulate body temperature is impaired so in a clever sort of...
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