Can a Sauna Help You Sleep?

The strongest evidence for heat before bed is not about saunas at all. A 2019 systematic review of 17 studies found that a bath or shower at 40 to 42.5°C, taken one to two hours before bed, was associated with shorter sleep onset latency and better self-rated sleep quality, with the authors' own university putting the average at roughly ten minutes faster to sleep. No controlled trial has put people in a sauna cabin and measured their sleep. Sauna users report the effect consistently, but that is survey data rather than trial data. The most defensible conclusion is that evening heat may help sleep, but the sauna-specific evidence is still limited.

What does the research say about heat before bed and sleep?

The anchor study is a systematic review and meta-analysis published in Sleep Medicine Reviews in 2019. Its authors screened 5,322 articles, included 17 and pooled data from 13. Their finding was that passive body heating with water at 40 to 42.5°C was associated with improved self-rated sleep quality and sleep efficiency. When the heating was scheduled one to two hours before bedtime for as little as ten minutes, it was also associated with a significant shortening of sleep onset latency. The University of Texas at Austin, where the lead author was based, summarised the pooled effect as falling asleep roughly ten minutes faster.

A Japanese crossover experiment published in the Journal of Physiological Anthropology in 2023 gives the same general result with the numbers on the surface. Twenty-three healthy adults, with a mean age of 39, bathed at home on separate nights under three conditions, all at roughly 40°C and all one and a half to two hours before bed: a shower only, a five-minute bath and a sixteen-minute bath. Time to fall asleep was 20.3 minutes after the shower, 16.1 minutes after the short bath and 12.3 minutes after the long bath. Subjective ratings of falling asleep and sleep quality were also significantly better after the long bath. Sleep efficiency and wake after sleep onset moved in the same direction, but neither reached statistical significance at that sample size.

Is there any research on saunas specifically and sleep?

This is where the evidence becomes much thinner.

The evidence I found does not include a controlled trial putting participants in a sauna cabin, traditional or infrared, and measuring subsequent sleep with a diary, actigraphy or polysomnography. What does exist is a substantial self-report survey of people who already use saunas.

The Global Sauna Survey, published in Complementary Therapies in Medicine in 2019, collected 482 valid responses, mainly from Finland, Australia and the United States. Of those respondents, 83.5 per cent reported sleep benefits after sauna use.

That is a striking number, but it needs to be read for what it is. These were people who already used saunas, answering a questionnaire about a habit they had chosen, with no comparison group and no objective measurement of sleep. The survey records what sauna users believe about their sleep, which is useful information about the experience, without establishing that sauna bathing caused the improvement.

Study	Participants	Heat used	Sleep result
Haghayegh et al 2019, meta-analysis	17 studies, 13 pooled	Water at 40 to 42.5°C, 1 to 2 hours before bed	Shorter sleep onset latency, better self-rated quality and sleep efficiency
Maeda et al 2023, randomised crossover	23 healthy adults	Bath at about 40°C for 16 minutes	Time to fall asleep 20.3 down to 12.3 minutes versus showering
Global Sauna Survey 2019, cross-sectional	482 sauna users	Sauna bathing, self-reported	83.5 per cent reported sleep benefits

Why might heat before bed affect sleep?

The useful part may be what happens after the heating rather than the heating itself. Body temperature normally falls as sleep approaches. One way the body manages that is by moving blood towards the hands and feet and releasing heat through the skin.

Researchers can measure this using the distal-to-proximal skin temperature gradient. A wider gradient indicates that heat is being transferred away from the body's core towards the skin and extremities.

The 2023 crossover study measured changes in body temperature directly. A sixteen-minute bath at 40°C raised sublingual temperature by 0.91°C, compared with 0.31°C for the short bath and 0.10°C for the shower. It was then followed by a significantly steeper fall in temperature between bathing and bedtime and a significantly wider skin temperature gradient before sleep.

The authors were careful about the mechanism, however. The subsequent fall in temperature is a result of heat loss and is not necessarily the direct cause of drowsiness. The wider temperature gradient appears to be the more relevant part of the process.

That gives us a plausible explanation for why evening heat may help sleep, but it still does not turn bath research into sauna research. A sauna heats the body in a different way and to a different extent, so the evidence should not be stretched further than it allows.

When should you use a sauna before bed?

No study has tested a sauna schedule specifically for sleep, so any timing advice here is necessarily read across from the bathing literature and the underlying mechanism.

Both point towards heating the body around one to two hours before bed, followed by enough time for a proper cool-down.

For an 11pm bedtime, that could mean finishing an evening sauna session at around 9.30pm rather than getting out at 10.30pm and going straight to bed. The point is not that 9.30pm is a magic time. It is that the body needs time to lose the heat generated by the session.

In practical terms, allow yourself to cool down properly before bed rather than getting straight into pyjamas while you are still hot. A cool shower, sitting outside or simply spending some time in a cooler room can all form part of that transition.

The important qualification is that this timing comes from research into warm bathing, not controlled sauna trials. It is therefore a reasonable starting point rather than a proven sauna prescription.

Is a sauna worth buying specifically to improve sleep?

If sleep is the only reason you are considering a sauna, the sensible first experiment is much cheaper.

The intervention with the strongest evidence behind it is a warm bath or shower. You can test that tonight without buying any equipment, and you can repeat it for a couple of weeks to see whether the timing and heat make a noticeable difference to your own sleep.

A sauna makes a different proposition. It gives you a repeatable evening routine built around heat, time away from everyday distractions and a deliberate period of cooling afterwards. Better sleep may be part of the experience for some people, but the current evidence does not justify treating a sauna as a remedy for insomnia.

That distinction matters when you are considering spending several thousand pounds on a cabin. Buy a sauna because you want the sauna and expect to use it regularly. Treat better sleep as a plausible and commonly reported benefit rather than the sole justification for the purchase.

Who should be cautious, and when should you speak to a GP?

Poor sleep is a symptom rather than a diagnosis. The NHS defines long-term insomnia as trouble sleeping that lasts three months or more and advises speaking to a GP if changing your sleep habits has not helped, if the problem has lasted for months or if it is affecting your daily life.

The NHS identifies cognitive behavioural therapy as a treatment for insomnia and notes that sleeping pills are generally prescribed only for short periods. If your sleep has been poor for months, it makes more sense to investigate the problem properly than to assume a sauna will solve it.

On sauna bathing itself, a 2018 prospective cohort study of 1,688 Finnish adults reported that people with a previous myocardial infarction, stable angina or heart failure can usually enjoy sauna bathing without significant adverse cardiovascular effects when their condition is stable. The same research advises caution for older people prone to orthostatic hypotension and notes the importance of adequate hydration.

Sauna bathing also places a cardiovascular demand on the body. The study recorded heart rates during sauna bathing of around 120 to 150 beats per minute, comparable with light to moderate exercise.

Pregnancy requires particular caution. The NHS notes that there is limited research on sauna use during pregnancy and that overheating can raise core temperature, with particular concern during the first twelve weeks. Increased blood flow to the skin can also contribute to faintness.

If you have a heart condition, are pregnant, take regular medication or have concerns about whether sauna bathing is appropriate for you, speak to your GP before starting.

What this means when choosing a sauna

If evenings are the use case, one of the most useful specifications is heat-up time rather than maximum temperature.

A cabin that takes 45 minutes to reach its operating temperature has to be switched on well before the session itself begins. For an evening routine, a heater with a suitable timer or remote-start function may therefore be more useful than simply choosing a higher-powered heater.

Ask for the manufacturer's published heat-up time rather than assuming that the stated maximum temperature tells you how quickly the cabin will reach it.

Siting is the second consideration. A cabin at the bottom of a long garden may be less convenient in winter than one close to the house, particularly when you want to cool down afterwards. Somewhere near the back door, with a suitable path and a sheltered place to cool down, may make the routine easier to maintain.

Our Plan your space page covers the practical questions around siting.

On sauna type, the evidence gives no basis for saying that traditional or infrared is better for sleep. Neither has been tested in a controlled sleep study that would allow that conclusion.

The sleep research used water at 40 to 42.5°C, so it is not directly comparable with either sauna type. Choose on the factors you can actually establish: how the heat feels, how long the room takes to warm, the electrical requirements and what it costs to operate.

A 6 kW heater in a family-sized cabin uses roughly 7 to 9 kWh across a two-hour session under Harvia's published consumption example. Heater sizing also follows published calculations rather than simply choosing a heater because its maximum output sounds impressive. Our guide to sauna heater sizing works through the calculation.

For the broader choice between appliance types, see our comparison of wood-fired and electric saunas. For the wider evidence around sauna use, see what the research shows about saunas and health and our article on saunas and back pain.

The range is in our sauna collection.

So, can a sauna help you sleep?

Possibly, but the evidence is not as straightforward as the marketing often suggests.

There is good evidence that passive heating through a warm bath or shower before bed can shorten the time it takes to fall asleep and may improve aspects of perceived sleep quality. The strongest evidence points towards heating the body around one to two hours before bedtime and allowing enough time afterwards for cooling.

There is also a large survey in which 83.5 per cent of sauna users reported sleep benefits. But that is self-reported observational evidence, not a controlled trial.

So the honest answer is that a sauna may help some people sleep, and the mechanism is plausible, but we do not yet have strong controlled evidence showing that sauna bathing itself improves sleep.

If sleep is your primary concern, test the simpler intervention first. If you want a sauna anyway, build it into an evening routine that gives you time to cool down afterwards and judge the experience for yourself.

Sources

• Haghayegh S, Khoshnevis S, Smolensky MH, Diller KR, Castriotta RJ. Before-bedtime passive body heating by warm shower or bath to improve sleep: a systematic review and meta-analysis. Sleep Medicine Reviews, 2019. doi:10.1016/j.smrv.2019.04.008
• University of Texas at Austin. Take a warm bath 1-2 hours before bedtime to get better sleep, researchers find, 19 July 2019.
• Maeda T, Koga H, Nonaka T, Higuchi S. Effects of bathing-induced changes in body temperature on sleep. Journal of Physiological Anthropology, 2023;42:20.
• Hussain JN, Greaves RF, Cohen MM. A hot topic for health: results of the Global Sauna Survey. Complementary Therapies in Medicine, 2019;44:223-234. Record at RMIT University research repository.
• Laukkanen T, et al. Sauna bathing is associated with reduced cardiovascular mortality and improves risk prediction in men and women. BMC Medicine, 2018.
• An international multidisciplinary Delphi-based consensus on heat therapy in musculoskeletal pain. Pain and Therapy, 2023.
• NHS. Insomnia.
• NHS. Is it safe to use a sauna or jacuzzi if I am pregnant?
• Harvia. FAQ about the energy consumption of sauna bathing.