The role of room temperature in quality sleep

Thermoregulation follows a 24-hour cycle linked with the sleep-wake rhythm.

Sleep and body control of temperature (thermoregulation) are intimately connected. This happens because sleep-wake rhythm and core body temperature both follow a 24-hour cycle. Mammals have evolved to sort stuff like this automatically. As a result our 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 (night), and much less likely to occur during the rises (day). No wonder that one of the best biohacks for sleep is cooling down a bedroom before going to sleep. If you get cold you may wear socks but it’s vital to have a lower room temperature in a bedroom for a sound and quality sleep.

Have you ever noticed how your hands and feet get colder in the evening? It’s because they 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. This mechanism is fueled by the sleep hormone melatonin, which plays an important part of the complex loss of heat through the peripheral parts of the body, namely hands and feet. Colder feet and hands signal, therefore, it’s high time to go to sleep.

Role of room temperature

Peripheral skin 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 body temperature and sleep.

Any major variation in ambient temperature 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).

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.

“During REM sleep, our ability to regulate body temperature is impaired so in a clever sort of way the body “avoids” this stage of sleep during extreme cold or heat. A heat wave may cause several nights of fragmented sleep with less slow wave and REM sleep”. 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.

The best temperature for sleep

You may wonder, and rightfuly so, what the best room temperature for sleep is. It seems that the best room temperature for sleep is between 15 and 19 degrees Celsius for adults. That mild drop in body temperature induces sleep. Generally “if you are in a cooler [rather than too-warm] room, it is easier for that to happen.” But if the room becomes uncomfortably hot or cold, you are more likely to wake up, says Ralph Downey III, PhD, Chief of Sleep Medicine at Loma Linda University. He further explains that the comfort level of your bedroom temperature also especially affects the quality of REM (rapid eye movement) sleep, the stage in which you dream.

The ideal temperature range varies slightly with age. The optimal range for seniors and children is a little warmer at 19 to 21 degrees and 18 to 21 degrees, respectively. A lot of this will depend on personal preferences, though, as some people naturally sleep hot while others prefer it cold. Also, it’s perfectly normal to set your room temperatures above or below these recommended temperatures until you feel comfortable. However, the best temperature for sleep is usually cooler.