Short answer
Cooler than hot, yes. Colder is not always better. Heat clearly hurts sleep: in a 2023 study of older adults, sleep was most efficient with the bedroom between 68 and 77 °F and fell 5 to 10% as it warmed from 77 to 86 °F. Under bedding, cool rooms did not change sleep stages in lab studies. We found no trial that proves one number such as 65 °F.
Heat is the proven problem
A 2012 review in the Journal of Physiological Anthropology found that when people sleep with normal bedding and clothing, heat increases wakefulness and cuts deep and REM sleep. Humid heat is worse.
Outside the lab, a 2017 study in Science Advances matched answers from 765,000 US survey respondents, collected from 2002 to 2011, with local nighttime temperatures. Warmer nights meant more reported nights of insufficient sleep. The effect was largest in summer and among lower-income and elderly respondents.
What a home study measured
In 2023, Boston researchers tracked older adults in their own homes with wearable sleep monitors and bedroom sensors. Sleep was most efficient and restful when the nighttime temperature was between 20 and 25 °C (68 to 77 °F). Sleep efficiency dropped by 5 to 10% as the room warmed from 25 to 30 °C (77 to 86 °F).
Two limits. The study was observational and only in older adults. And the authors reported substantial differences between people, which matches what you see at home: the best temperature is personal.
Is colder better?
Not on the evidence so far. The 2012 review reports that in studies where people used bedding, sleep did not differ significantly across room temperatures from 13 to 23 °C (55 to 73 °F). Covers keep the temperature next to your body fairly constant.
It is different without covers. In lightly dressed sleepers, rooms colder or hotter than neutral increased wakefulness. The review also found that cold rooms changed heart-rate patterns during sleep even when sleep stages looked normal, and the authors asked for more research on cold.
Where the 65 °F figure stands
You will see 65 °F quoted widely. We could not find a controlled trial that tested 65 °F against other settings, so we do not state it as a fact.
The official advice is less exact. The American Academy of Sleep Medicine's healthy sleep habits page, updated in August 2020, says to keep the room at a comfortable, cool temperature and gives no number. The National Institute on Aging says comfortable, not too hot or too cold. A reasonable reading: avoid a warm bedroom, then adjust until you sleep through.
Related questions
What is the best bedroom temperature for sleep?
No single number is proven. In one 2023 study of older adults, sleep was most efficient between 68 and 77 °F, with large differences between people.
Can a room be too cold to sleep well?
With enough bedding, lab studies found no significant change in sleep stages in cool rooms. Without covers, cold increased wakefulness.
Does a hot bedroom really cost you sleep?
Yes, that is the best-supported finding. Heat increases wakefulness and reduces deep and REM sleep, according to a 2012 review.
Read next
Sources
- Baniassadi et al., Science of the Total Environment: Nighttime ambient temperature and sleep in community-dwelling older adults (2023)
- Okamoto-Mizuno & Mizuno, Journal of Physiological Anthropology: Effects of thermal environment on sleep and circadian rhythm (2012)
- Obradovich et al., Science Advances: Nighttime temperature and human sleep loss in a changing climate (2017)
- American Academy of Sleep Medicine: Healthy Sleep Habits (updated 2020)
- National Institute on Aging: Sleep Problems and Menopause (reviewed 2021)
Published 2026-10-04 · Last checked 2026-10-04
Educational content, not medical advice. Made for the United States.