Cool down to bed The importance of body temperature for sleeping and the secret powers of a warm shower

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You’re sitting around a campfire, you’ve finished eating, it’s going dark, conversation is dwindling and it’s cooling down. Your body knows it’s soon time to sleep and you get tried. Pretty soon you’re fast asleep. Bedtime for a caveman was pretty simple. But I don’t live in a cave so how will this help me to sleep easier?

Your body has evolved to recognise many cues to make you tired and ready for sleep. As we’ve discussed, modern life is making many of these cues hard for us to recognise or removing them altogether. However, we know that cooling down before bed is one of these important cues and one you can control relatively easily.

Whilst you’re asleep your body tends to be 1 or 2 degrees cooler than during waking hours. This cool down begins before you fall asleep and continues when you’re asleep. This helps you fall asleep and keeps you asleep. This is why excessive exercise just before bedtime can be very disruptive to sleep as it can heat you up.

So how to cool down

The obvious place to start is with your heating. My suggestion is have your heating go off well before you intend to get into bed. My heating turns itself off an hour and half before I get into bed (two hours before I intend to fall asleep). This gives my flat and importantly my body time to cool down. Don’t underestimate how long this will take. Perhaps trial a few different times and see what works for you.

If you don’t want to start the cooling down process ahead of bedtime then ideally you want a noticeable change in temperature between your bedroom and the rest of your house. Think about trying to get your bedroom as similar to a cave as you can, dark, quiet and cool (but no spiders or bears).

It’s worth paying particular attention to the temperature of your bedroom. Either turning the heating down sooner or having it on a lower heat can help cool your bedroom down quicker.

Controlling a cool down in your home is a lot easier if you live in a cold country. This is very much true for England in the winter (I’m writing this in February with the heating at full blast!).  Lucky enough to live in a hot climate?  Then think about how you can start to reduce the temperature before bed. If this means having your home slightly warmer during the day so you can feel the drop in temperature I’d recommend trying this out. If not, then using the aircon wisely can really help.

Aircon is also the favourite of holiday makers and can be a great tool in sleeping better on holiday. Be careful not to have the air-con on too low during the night time if the day time temperatures are hot. This can play havoc with your body. However, using the aircon to bring your room and body temperature down in a controlled way can really help you sleep.

Warming up for bed

One tip I regularly recommend and something I do for myself is take a hot shower or bath about 30 – 60 minutes before bed.

Hang on. I thought we were trying to cool down?

Having a warm soak before bed is actually a great way of cooling down. When you’re exposed to a hot environment – in this case a shower – your body reacts by pumping blood to your arms, leg and surface of your skin to cool you down. This is called vasodilation and works to remove heat from your core so it can be lost to the environment. This process (and its opposite, vasoconstriction) is a key part of homeostasis.

Through vasodilation your body reduces your core temperature and when you get out of the shower or bath your temperature quickly falls, signalling to your body it’s time to start getting ready for sleep.

Showers and baths of course have the added benefit of being very relaxing and away from other disturbances. I find them almost meditative as you concentrate on running through a well known sequence as your mind relaxes down. Perfect for bed.

Written by
Sam Billington

Sam is our sleep guru. I am fascinated by sleep and I've used my science training to research and learn about sleep. I have been providing sleep advice and personal sleep plans for years. My day job is Head of Workplace Culture in Defra, I live in London with my wife and have a PhD in Ecology and Biology.