The National Sleep Foundation recommends somewhere between 60 and 67 degrees Fahrenheit (15.5 and 19.4 degrees Celsius), although it can vary for each person.1 A general rule of thumb is that a cooler room helps you sleep better. Two hours before falling asleep, your body temperature starts to decrease to help prepare you for sleep.2 It's part of your circadian sleep-wake cycle.2 A lower temperature signals your body that it's time to sleep, and an increase in temperature signals that it's time to wake up.2
When your room is too hot, you might sleep less deeply, dream less, and wake up more frequently.3 This is because your body can cope with the increase in temperature when you are awake but struggles to regulate when you're asleep.3
However, going too cold can be bad for sleep too. Extra cold room temperatures can cause your body to work harder to maintain your internal temperature, and your heart rate to increase during sleep.3 This could actually be why heart attack rates are higher in the winter.4
How to Create a Cooler Sleep Environment
How do you cool your room down to create those ideal sleeping conditions? Well, be aware that opening a window or using air-conditioners might not be the answer. A study has shown that airflow directly blowing on you, even if it's very low, might cause you to wake up more frequently and sleep less deeply.5 Keep drafts to a minimum if you can and try these tips:
- Use blackout curtains to keep your room from getting too hot and wear lighter, breathable fabrics while you sleep
- Don't exercise close to bedtime, as this can raise your body temperature for several hours and keep you more alert
- Take a shower or bath before bed
- Look for sheets and pillowcases made of material that stays cooler longer
You can even get a mattress topper filled with water that is cooled before you go to bed, sometimes to 60 degrees Fahrenheit (15.5 degrees Celsius) or lower. Some even come with a feature that warms the mattress topper slightly in the morning, to help you wake up.
As you can see, sleep temperatures can have a surprising impact on the quality of your sleep and it can be a balancing act to get the temperature just right. But even if your partner doesn't want the room as cool as you do, there are plenty of workarounds you can use to help cool down your body. You don’t need to wait until the seasons change to get a good night’s sleep.
1 National Sleep Foundation. The Ideal Temperature for Sleep. Online. https://www.sleep.org/temperature-for-sleep/ Last accessed Nov 13, 2020.
2 Okamoto-Mizuno, Kazue, and Koh Mizuno. “Effects of thermal environment on sleep and circadian rhythm.” Journal of physiological anthropology vol. 31,1 14. 31 May. 2012, doi:10.1186/1880-6805-31-14
3 Okamoto-Mizuno, Kazue, and Koh Mizuno. “Effects of thermal environment on sleep and circadian rhythm.” Journal of physiological anthropology vol. 31,1 14. 31 May. 2012, doi:10.1186/1880-6805-31-14
4 Okamoto-Mizuno, K., Tsuzuki, K., Mizuno, K. et al. Effects of low ambient temperature on heart rate variability during sleep in humans. Eur J Appl Physiol 105, 191 (2009). https://doi.org/10.1007/s00421-008-0889-1
5 Naomi Morito, Kazuyo Tsuzuki, Ikue Mori, Hajime Nishimiya, Effects of two kinds of air conditioner airflow on human sleep and thermoregulation, Energy and Buildings, Volume 138, 2017, Pages 490-498, ISSN 0378-7788, https://doi.org/10.1016/j.enbuild.2016.12.066.