The Temperature Dependence of Sleep

Abstract

Mammals have evolved a range of behavioural and neurological mechanisms that coordinate cycles of thermoregulation and sleep. Whether diurnal or nocturnal, sleep onset and a reduction in core temperature occur together. Non-rapid eye movement (NREM) sleep episodes are also accompanied by core and brain cooling. Thermoregulatory behaviours, like nest building and curling up, accompany this circadian temperature decline in preparation for sleeping. This could be a matter of simply comfort as animals seek warmth to compensate for lower temperatures. However, in both humans and other mammals, direct skin warming can shorten sleep-latency and promote NREM sleep. We discuss the evidence that body cooling and sleep are more fundamentally connected and that thermoregulatory behaviours, prior to sleep, form warm microclimates that accelerate NREM directly through neuronal circuits. Paradoxically, this warmth might also induce vasodilation and body cooling. In this way, warmth seeking and nesting behaviour might enhance the circadian cycle by activating specific circuits that link NREM initiation to body cooling. We suggest that these circuits explain why NREM onset is most likely when core temperature is at its steepest rate of decline and why transitions to NREM are accompanied by a decrease in brain temperature. This connection may have implications for energy homeostasis and the function of sleep.

Sleep deprivation triggers somatostatin neurons in prefrontal cortex to initiate nesting and sleep via the preoptic and lateral hypothalamus

“…Usually mammals undertake specific behaviors before sleep or as they become drowsy [1][2][3][4][5][6] . We humans put on bed clothes, lie down and tend to curl up in bed.…”

“…In other mammals sleep preparatory behaviors, such as building a nest, and going to a nest in a burrow, seem innate. Nesting serves both as a protective environment in which predators can be avoided while sleeping, and provides a thermal microclimate, promoting skin warming that in turn induces NREM sleep 3,7 . In mice, nest building prior to sleep can be initiated by decreasing the activity of dopamine neurons in the midbrain ventral tegmental area 1 .…”

Sleep Environment and Non-Rapid Eye Movement-Related Parasomnia Among Children: 42 Case Series

“…This difference in subjective thermal perceptions between children and mothers may have made the mother act to warm the thermal environment. The exposure of heat or cold is one of the critical factors that can affect sleep stages [14]. Too much heat exposure by thermoregulatory behavior such as bedding or clothing can increase wakefulness and decrease slow wave sleep and REM sleep, but cold exposure did not impact the sleep stage [15].…”

Fundamental Concepts of Human Thermoregulation and Adaptation to Heat: A Review in the Context of Global Warming

“…The weather condition is ubiquitous with human existence, behavior, and functions [35]. For example, the type of dressing, design of homes and buildings, sleep-wake cycles, and the profile of daily activities are influence by seasonal changes in weather conditions [36][37][38]. Global warming would have even greater impact on those who engage in physical work in the outdoors, such as laborers, farmers, military personnel, and fire-fighters [39][40][41][42][43][44][45].…”