Achieve thermoneutrality for better sleep

Intro

It is summer. The day is so beautiful you wish it would never end, but night follows the sun as inevitable as life to amino acids in water. And what started as a nice comforting invitation to the beach, the forest or a nearby café turns into a humid sweatfest in the confines of the bedroom.

No turning, or opening of the window can put an end to the feeling of “It’s too damn hot!”.

If you too have suffered under the brute force of heat when trying to sleep, then open a window and put on some tea while you join us on our little dip into the…

Influence of hot and cold temperatures on sleep

Sleep and temperature

When it comes to sleep and temperature, our common body behaves a little diva’ish.
^{Only the best thermoneutrality for this body.}

Only the best thermoneutrality is good enough to allow proper sleeping conditions [Bach 1994, Caddick 2018, Candas 1982, Haskell 1981, Togo 2007].

Where is the thermoneutral zone?

What it means is that the ambient temperature (meaning the room) should be 28ºC (82.4 ºF for those imperials among our dear readers) in naked conditions to maintain a core temperature of 36-38˚C (96.8-100.4˚F) or skin temperature of 32˚C (89.6˚F) [Kingma 2014].

When we snuggle into bed and wear comfy pajamas, the ambient temperature to achieve thermoneutrality falls of course. For men 17ºC (62.6 ºF) and women typically 23ºC (73.4 ºF) [Pan 2012].

And the common sleeper, motivated by hours of keen activity, does well to aim for that thermoneutral zone. If they don’t disaster looms in the darkness.

How does temperature do?

High or low temperatures worsen our ability to fall asleep. If we are too hot or too cold, our bodies have a thing or two to say about our mood, behaviour, thoughts and general abilities, such as our ability to rest [Bach 1994, Caddick 2018, Candas 1982, Haskell 1981, Togo 2007].

And even if we do fall asleep, temperature can rip us out of it like an over jealous sibling.
^{Don’t we love those?}

As we pointed out in [[« Article – REM Sleep]], REMS doesn’t take the greatest care to regulate our body temperature [Parmeggiani 2011]. So, if the skin temperature is already at the edge of the thermoneutral zone, it could fully fall out of it once REMS takes over and lessens sleep’s gentle thermocontrols.

Partly caused by the release of [[§ Melatonin|melatonin]], over the course of sleep our body temperature also continuesly decreases [Cagnacci 1997, Dijk 2002, Krauchi 1994, Senses 2013]. A fact that our bodies make good use of since [[§ NREM3|NREMS3]] improves when the skin temperature falls over the course of sleeping [Togo 2007].

Outro

Therefore listen to your body and either set the room-temperature to adequate levels or adjust your personal thermal shield with pillows, blankets and night-wear to keep the forces of heat and cold at bay.

Sources

Key	Citation
Bach 1994	Bach, V., Maingourd, Y., Libert, J. P., Oudart, H., Muzet, A., Lenzi, P., & Johnson, L. C. (1994). Effect of continuous heat exposure on sleep during partial sleep deprivation. Sleep, 17(1), 1-10.
Cagnacci 1997	Cagnacci, A., Kräuchi, K., Wirz-Justice, A., & Volpe, A. (1997). Homeostatic versus circadian effects of melatonin on core body temperature in humans. Journal of biological rhythms, 12(6), 509-517.
Candas 1982	Candas, V., Libert, J. P., & Muzet, A. (1982). Heating and cooling stimulations during SWS and REM sleep in man. Journal of Thermal Biology, 7(3), 155-158.
Dijk 2002	Dijk, D. J., & Lockley, S. W. (2002). Invited Review: Integration of human sleep-wake regulation and circadian rhythmicity. Journal of applied physiology, 92(2), 852-862.
Haskell 1981	Haskell, E. H., Palca, J. W., Walker, J. M., Berger, R. J., & Heller, H. C. (1981). The effects of high and low ambient temperatures on human sleep stages. Electroencephalography and clinical neurophysiology, 51(5), 494-501.
Kingma 2014	Kingma, B. R., Frijns, A. J., Schellen, L., & van Marken Lichtenbelt, W. D. (2014). Beyond the classic thermoneutral zone: including thermal comfort. Temperature, 1(2), 142-149.
Krauchi 1994	Krauchi, K., & Wirz-Justice, A. N. N. A. (1994). Circadian rhythm of heat production, heart rate, and skin and core temperature under unmasking conditions in men. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology, 267(3), R819-R829.
Pan 2012	Pan, L., Lian, Z., & Lan, L. (2012). Investigation of gender differences in sleeping comfort at different environmental temperatures. Indoor and Built Environment, 21(6), 811-820.
Parmeggiani 2011	Parmeggiani, P. L. (2011). Systemic homeostasis and poikilostasis in sleep: Is REM sleep a physiological paradox?. World Scientific.
Senses 2013	Senses, H. (2013). The Human Ear-Hearing, Sound Intensity and Loudness Levels.
Togo 2007	Togo, F., Aizawa, S., Arai, J. I., Yoshikawa, S., Ishiwata, T., Shephard, R. J., & Aoyagi, Y. (2007). Influence on human sleep patterns of lowering and delaying the minimum core body temperature by slow changes in the thermal environment. Sleep, 30(6), 797-802.