How to hack your body temperature for deeper sleep

by Dr Eidn

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In this article we'll tell you about the top 3 ways you can manipulate your body’s temperature in order to consistently get a better night of deeper sleep. 

Have you ever noticed in the summer, or when you’re on holiday in a hot country, you often spend all night tossing and turning in bed, struggling to sleep? That’s because we all need to drop our core body temperature by around 1℃ ( or 2℉) in order to get a sound night of sleep, and this is much more difficult when our surroundings are too warm. Studies in fact have shown that our sleep quality is much worse when we are too warm at night. We end up with both less deep sleep (which helps us feel restored and well rested), and with less REM or dream sleep (which helps us with regulating our emotions amongst many other things).

Our body’s natural 24-hour circadian rhythm will help us to lose heat through our skin in the evening, which helps us to fall asleep at night. But there’s a few things that we can do ourselves to really kick-start this temperature change. These tips will help us get to sleep faster, and have a deeper and more restorative night’s sleep. 

What temperature should my bedroom be at night?

The first tip is simple - make your bedroom cooler. Not only will this help you save on your energy bills, but it also gets you a better night’s sleep. Most people have their bedroom too warm which impairs your body’s ability to lose heat and leads to worse quality sleep. These days most sleep experts recommend a bedroom temperature of 16-18℃ (that’s 62 -65℉). This is the optimum ambient temperature for most people which keeps your body at just the right temperature through the night, to give you the deepest most restorative sleep.

Too cold a bedroom can also have a negative effect on your sleep, as well as potential impacts on other areas of health, so 16-18℃ (or 62 -65℉) is just right for most people.

Does having a bath or shower help with sleep?

The second tip is to take a hot bath or shower before bed. But hang on a second, didn’t I just say we need our bodies to cool down in order to fall asleep? Isn’t having a hot bath going to have the opposite effect?

Well, yes and no. You’d be right that having a hot bath or shower will warm you up, yes of course. But it’s what happens when you get out of the bath or shower that makes the difference here. You see when you’re all nice and toasty in your hot bath, your body realises that it’s too warm, so all the tiny little blood vessels in your skin get bigger and more blood is drawn from your body’s core to the surface of the skin, which helps it to lose heat and stop you from overheating.

This is why people look flushed when exercising, or on a hot summer’s day - it’s our body’s own way of losing heat if we’re getting too hot. And this is exactly what happens in a hot bath or shower too. But it's what happens after the bath or shower that's important. When we get out, there is still lots of blood circulating close to the surface of our skin, and so this leads to rapid loss of heat which cools down our core and helps us to fall asleep quicker. This effect has been clinically proven in a number of studies (see references).

Do cold feet stop you sleeping?

The third tip is another simple one - wear socks to bed. I know, I know… it's really not very sexy is it? But did you know there’s actually nothing sexier than a good sleeper - they are generally healthier, subjectively more attractive to others, and just much nicer to be around. So I think your other half will forgive you for wearing socks to bed if you tell them this - and if you show them the study linked in references below, which found that wearing bed socks helped people fall asleep quicker and have better quality sleep too.

How does this work? Well, if you have cold feet, this sends a signal to your brain that your body is cold. And so your body keeps as much blood as it can away from your skin and extremities in order to preserve heat. This keeps your core body temperature warm but it impairs your ability to sleep, as we’ve learned that your core body temperature needs to drop by 1℃ in order to promote sleep.

Now if we wear bed socks to keep our feet warm at night, this sends the signal to our brain that we are warm enough already. This in turn means more blood circulates near the skin, and so we lose core body heat which helps us to fall asleep faster - and to stay asleep through the night. Just remember to tell your partner that it’ll be worth it as you’ll look more attractive in the morning!

References

Ambient temperature and human sleep. Muzet, J. P. Libert, and V. Candas. Experientia, 40(5):425–429, May 1984

Effects of thermal environment on sleep and circadian rhythm. Kazue Okamoto-Mizuno, Koh Mizuno. Journal of Physiological Anthropology, 31(1):14, December 2012

The effects of increased bedroom air temperature on sleep and next-day mental performance. Peter Strøm-Tejsen, Sigrid Mathiasen, Marlene Bach, Steffen Petersen. Indoor Air, Volume26, Issue5, October 2016

Before-bedtime passive body heating by warm shower or bath to improve sleep: A systematic review and meta-analysis. Shahab Haghayegh, Sepideh Khoshnevis, Michael H Smolensky, Kenneth R Diller, Richard J Castriotta. Sleep Med Re v. 2019 Aug;46:124-135

Effects of feet warming using bed socks on sleep quality and thermoregulatory responses in a cool environment. Yelin Ko, Joo-Young Lee. J Physiol Anthropol, 2018 Apr 24;37(1):13