The sleep-friendly bedroom: temperature, light and noise, by the evidence.
Built from a review of thermal-environment sleep studies, laboratory studies of light before and during sleep, and systematic reviews of noise, white noise and earplugs.
There is no proven ideal bedroom temperature. With normal bedding, lab studies found sleep unchanged between 13 and 23°C (55-73°F); heat, especially humid heat, is what cuts deep and REM sleep. Beyond temperature, the evidence points to two more fixes: keep the room dark during sleep and dim in the evening, and block noise rather than masking it.
Most bedroom advice online is a list of twenty tips of equal weight: paint colours, plants, a tidy nightstand, one magic thermostat number. The research is narrower and more useful than that. Three things in a bedroom have measurable effects on sleep or on the body during sleep: heat, light and noise. This guide goes through what the studies found for each, what they did not find, and the practical fix for each one.
| Factor | What the research found | What to do |
|---|---|---|
| Room temperature | With bedding, no difference in sleep from 13 to 23°C (55-73°F); heat and humid heat increase waking and cut deep and REM sleep | Keep the room and the bed from getting hot; lighter, breathable bedding in warm weather |
| Winter cold | With covers, cold did not change sleep stages but did change heart activity during sleep | Keep the bedroom above 10°C (50°F) |
| Evening light | Ordinary room light before bed delayed melatonin onset in 99% of people and shortened melatonin by about 90 minutes | Dim the lights in the hours before bed |
| Light during sleep | One night at 100 lux raised heart rate and next-morning insulin resistance compared with a dim room | Blackout curtains or a sleep mask |
| Noise | Disturbs sleep and causes daytime sleepiness | Reduce it at the source, then block it with earplugs |
| White noise | Evidence that it improves sleep rated very low quality | Optional, at low volume; not a treatment |
Temperature: there is no magic number
Articles on the "ideal sleep temperature" usually quote one number. The research does not support one. A 2012 review of thermal-environment studies found that when people slept with normal bedding and clothing, sleep did not differ significantly across room temperatures from 13 to 23°C (about 55 to 73°F), and in another study from 3 to 17°C.[1] Bedding and clothing do most of the work. What matters is the bed climate: the pocket of air between your skin and the covers.[1]
The same review is clear about what does hurt. With bedding and clothing on, heat increases wakefulness and reduces slow-wave (deep) sleep and REM sleep, and humid heat adds to the load.[1] The 29°C (84°F) "thermoneutral" figure that sometimes gets quoted comes from people sleeping nearly unclothed, not from a normal bedroom.[1]
Cold works differently. With covers, cold did not change sleep stages, but it did change heart activity during sleep without people noticing it, which is why the review's authors say a bedroom in winter should stay above 10°C (50°F).[1]
In practice, the goal is not to hit a number but to stop the room and the bed from getting hot. A fan or air conditioning in warm weather, lighter and more breathable bedding, and a mattress that does not trap heat all work on the same problem. If the room is hot and humid, bringing the humidity down matters as well as the temperature.
Light: the room light you don't notice
In a study of 116 healthy adults aged 18 to 30, spending the eight hours before bed in ordinary room light (under 200 lux) instead of dim light (under 3 lux) delayed the start of melatonin release in 99% of people and shortened the body's melatonin night by about 90 minutes.[2] Room light during the usual hours of sleep suppressed melatonin by more than half in 85% of trials.[2]
Light during sleep itself matters too. In a 2022 laboratory study, healthy adults who slept one night in moderate (100 lux) light had a higher heart rate during the night and more insulin resistance the next morning than when they slept in a dim room.[3]
In practice: dim the lights in the evening, and make the room itself dark while you sleep. Blackout curtains deal with streetlight and early sunrise; a sleep mask does the same job with nothing to install, and travels. If a fully dark room makes mornings hard, a sunrise alarm clock brightens gradually at your wake time.
Noise: block it before you mask it
Environmental noise disturbs sleep and causes daytime sleepiness, and long-term exposure is linked with high blood pressure and heart disease.[4]
The most popular fix, a white noise machine, has weaker support than its sales suggest. A 2021 systematic review of 38 papers rated the quality of evidence that continuous noise improves sleep as very low, and warned that it may also harm sleep and hearing.[5]
Earplugs have somewhat better, though still limited, evidence. In a laboratory study, healthy people exposed to recorded intensive-care noise and light got more REM sleep, fewer arousals and higher melatonin when they wore earplugs and eye masks.[6] A Cochrane review of intensive-care patients found low-quality evidence that earplugs or eye masks increase total sleep time.[7]
In practice: reduce noise at the source where you can, then block what is left with earplugs. If you use a sound machine to cover intermittent noise, keep the volume low and treat it as a comfort rather than a treatment.
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Get the 12 free printables →What the bedroom-tip boards promise that research doesn't
Some of the most shared bedroom advice has no sleep research behind it. We searched PubMed for studies testing bedroom wall colour against sleep and found none. A calming colour may make a room more pleasant to be in, but no study shows it changes how you sleep.
Aromatherapy is a different case: it has a small trial literature of its own, which our aromatherapy guide goes through. It is not covered here because it works on the person, not on the room's temperature, light or noise.
If you have fixed heat, light and noise and still sleep badly, the cause is probably not the room. Caffeine timing is the next thing to check, and it has its own guide on this site.
What actually moves the needle.
Each strategy below is rated by evidence strength, with the specific source and what it does and doesn't solve. Run them in order.
Keep the bed from getting hot
Aim to stop the room and the bed from overheating rather than to hit one number. Use a fan or air conditioning in warm weather, lighter and more breathable bedding, and lower the humidity if the room is humid. In winter, keep the room above 10°C (50°F).
- +Waking hot or sweaty
- +Restless sleep on warm nights
- −A racing mind at bedtime
- −Waking from light or noise
Dim the evening, darken the night
Lower the lights in the hours before bed, and make the room dark while you sleep with blackout curtains or a sleep mask.
- +Streetlight or early sunrise in the room
- +Bright lamps and overhead lights in the evening
- −Waking from noise or heat
Block noise first, mask it second
Reduce noise at the source where you can, then block what is left with earplugs. A sound machine is optional; if you use one, keep the volume low.
- +Traffic, neighbours, a snoring partner
- −Waking from heat or light
If you have fixed heat, light and noise and still have trouble falling or staying asleep at least three nights a week for three months, that pattern matches chronic insomnia, which is worth raising with a doctor. If a partner notices loud snoring, gasping or pauses in your breathing, ask about sleep apnea; no bedroom change treats it.
Related tools
People also ask
Is it better to sleep in a cold room?
Cooler is better than hot, but colder is not better without limit. With bedding, lab studies found no difference in sleep between 13 and 23°C (55-73°F). Colder than that, cold changed heart activity during sleep without disturbing sleep stages, and the review's authors advise keeping a bedroom in winter above 10°C (50°F).
Should you sleep with a light on?
The evidence says no. In a 2022 laboratory study, one night sleeping in 100 lux light raised healthy adults' heart rate during the night and their insulin resistance the next morning, compared with a dim room. If you need a light, keep it as dim as you can.
Do blackout curtains help you sleep?
They remove something shown to affect the body during sleep: light in the room. No trial has tested blackout curtains themselves; the evidence is for darkness, which blackout curtains or a sleep mask provide.
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FAQ
What is the ideal temperature for sleep?
No single temperature has been shown to be ideal. In a 2012 review of the research, people sleeping with normal bedding showed no significant difference in sleep across room temperatures from 13 to 23°C (55-73°F). What the studies do show is that heat, especially humid heat, increases waking and reduces deep and REM sleep. Aim to keep the room from getting hot, and in winter keep it above 10°C (50°F).
Is humidity bad for sleep?
Humid heat is worse than dry heat. The 2012 thermal-environment review found that humid heat adds to the load on the body during sleep and affects sleep stages and body-temperature regulation. If your bedroom is hot and humid, lowering the humidity helps as well as lowering the temperature.
Is white noise good for sleep?
The evidence is weak. A 2021 systematic review of 38 papers rated the quality of evidence that continuous noise improves sleep as very low, and noted it may also harm sleep and hearing. It can be worth trying to cover intermittent noise, at a low volume, but blocking noise with earplugs has better support.
Do earplugs help you sleep?
The evidence is limited but positive. In a laboratory study, people exposed to recorded intensive-care noise and light got more REM sleep and fewer arousals when they wore earplugs and eye masks. A Cochrane review of intensive-care patients found low-quality evidence that earplugs or eye masks increase total sleep time.
Does bedroom colour affect sleep?
There is no research showing it does. We searched PubMed for studies testing bedroom wall colour against sleep and found none. Choose a colour you like; spend the effort on temperature, light and noise instead.
This guide is a synthesis of published research: a 2012 review of thermal-environment sleep studies, laboratory studies of light before and during sleep, a Lancet review of noise and health, and systematic reviews of white noise and of earplugs and eye masks. Figures are taken from each paper's abstract or open full text. We did not test any product or bedroom setup ourselves. Where evidence is weak or missing, as for white noise and paint colours, the guide says so.
- [1]Okamoto-Mizuno K, Mizuno K. 'Effects of thermal environment on sleep and circadian rhythm.' Journal of Physiological Anthropology, 2012.
- [2]Gooley JJ, Chamberlain K, Smith KA, et al. 'Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans.' Journal of Clinical Endocrinology & Metabolism, 2011.
- [3]Mason IC, Grimaldi D, Reid KJ, et al. 'Light exposure during sleep impairs cardiometabolic function.' Proceedings of the National Academy of Sciences, 2022.
- [4]Basner M, Babisch W, Davis A, et al. 'Auditory and non-auditory effects of noise on health.' The Lancet, 2014.
- [5]Riedy SM, Smith MG, Rocha S, Basner M. 'Noise as a sleep aid: A systematic review.' Sleep Medicine Reviews, 2021.
- [6]Hu RF, Jiang XY, Zeng YM, et al. 'Effects of earplugs and eye masks on nocturnal sleep, melatonin and cortisol in a simulated intensive care unit environment.' Critical Care, 2010.
- [7]Hu RF, Jiang XY, Chen J, et al. 'Non-pharmacological interventions for sleep promotion in the intensive care unit.' Cochrane Database of Systematic Reviews, 2015.
Dr. Logan Foley, CSSC
Certified Sleep Science Coach (CSSC) trained through the Spencer Institute. Edits SleepyHero's adult-sleep tools, gear reviews, and articles.
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SleepyHero independently researches every article. We do not accept payment from supplement brands, sleep tracker manufacturers, or pharmaceutical companies for editorial coverage. Affiliate links to recommended tools support the site at no cost to you.
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A bedroom add-on with a small trial literature of its own.
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