Sauna and sleep: How heat exposure improves your sleep quality
Many people sleep deeper and better after time in the sauna. But what actually causes this calming effect? Science points to sauna bathing not only being relaxing for the mind, it also triggers a series of physiological processes that directly support better night-time sleep. In this article we look at the research behind sauna and sleep quality, and how you can use heat to optimise your rest.
The most important things to know
- 83.5% of regular sauna users report improved sleep after sauna bathing.
- Heat from the sauna raises body temperature, which is followed by a drop that signals to the body that it is time to sleep.
- Sauna bathing in the evening, 1-2 hours before bedtime, is thought to be most effective for sleep quality.
- Sauna can reduce stress and muscle tension, which further promotes deep, calm sleep.
The scientific link between sauna and sleep
Research into the health benefits of the sauna has grown significantly in recent years. One of the most notable findings is the positive effect on sleep. In a large global survey of sauna users, the "Global Sauna Survey", researchers found that 83.5% of respondents experienced sleep benefits after using the sauna [1]. The survey also showed that users primarily used the sauna for relaxation and stress reduction, which are important factors for a good night's sleep.
But why does it work? Much of the explanation lies in the body's temperature regulation and the natural circadian rhythm.
Body temperature and the natural circadian rhythm
Our sleep-wake rhythm is closely linked to core body temperature. During normal sleep, core temperature falls, and it rises again when we wake. Sleep starts most easily when body temperature is dropping [2].
When you spend time in a hot sauna, your body temperature rises markedly. The body responds by increasing blood flow to the skin to release heat. When you then leave the sauna and cool down, the body experiences a relatively rapid fall in core temperature. This drop mimics the natural process that happens just before we fall asleep, and works as a strong signal to the brain that it is time to rest.
This mechanism is reinforced by increased blood flow to the skin, especially hands and feet, which helps shed heat from the body's core. Research has shown that warming the skin, for example with a warm bath or a session in the sauna, can speed up sleepiness and improve sleep quality [3].
Sauna as a stress reducer
Beyond the direct effect on body temperature, the sauna's ability to reduce stress plays a crucial role for sleep. Stress and anxiety are among the most common causes of sleep problems.
When we are stressed, the body produces increased amounts of the hormone cortisol, which keeps us awake and on high alert. Sauna bathing has been shown to reduce cortisol levels and promote the release of endorphins, the body's natural "feel-good" hormones. This shift in hormonal balance creates a state of deep relaxation, which makes it easier to fall asleep and stay in deep sleep for longer.
Timing: When is sauna best for sleep?
To get the maximum sleep-promoting effect of sauna bathing, timing matters. If you go to the sauna right before you plan to sleep, the elevated body temperature and increased heart rate can actually be stimulating and make it harder to drift off.
Experts generally recommend finishing sauna bathing 1-2 hours before bedtime. This gives the body enough time to cool down and experience the helpful drop in core temperature that signals to the brain that it is time to sleep.
| Timing of sauna bathing | Expected effect on sleep |
|---|---|
| Morning / Late morning | Invigorating, increased energy during the day. Less direct effect on night-time sleep. |
| Afternoon | Relaxing, but body temperature has a long time to stabilise before bedtime. |
| 1-2 hours before bedtime | Optimal for sleep. The body experiences the necessary temperature drop just as you go to sleep. |
| Right before bedtime | May be too stimulating. Body temperature is still too high to promote sleep. |
Cold therapy combined with sauna
Many prefer to combine sauna bathing with cold therapy, for example a cold dip or an ice bath. This practice, often called contrast therapy, can also have a positive impact on sleep.
The cold shock after the hot sauna causes a rapid constriction of blood vessels, which helps flush waste products from muscles and reduce inflammation. Although an ice bath on its own can be very invigorating, the subsequent relaxation and marked fall in body temperature can contribute to even deeper sleep. If your primary aim is to improve sleep, it can be helpful to finish your contrast therapy with heat, or at least give your body plenty of time to return to a neutral temperature before bedtime.
More sleep-related benefits: Melatonin and muscle recovery
Another important factor in the link between sauna and sleep is the hormone melatonin. Melatonin is known as the "sleep hormone" and plays a central role in regulating our circadian rhythm. Some studies suggest that the deep relaxation and temperature effects from the sauna can support the body's natural evening melatonin production. As darkness falls and body temperature begins to drop after sauna bathing, the ideal conditions are created for melatonin levels to rise, which makes it easier to fall asleep and improves sleep quality.
In addition, the sauna's effect on muscle recovery is worth noting. After a long day or physical exertion, muscle tension and soreness can make it hard to find a comfortable sleeping position. The intense heat in the sauna increases blood circulation to the muscles, which speeds the removal of lactic acid and other waste products. This results in a noticeable reduction in muscle tension. When the body is physically relaxed and free from pain, there are fewer disturbances to interrupt sleep during the night, leading to more continuous and deep sleep.
Conclusion
There is strong scientific support for the old folk belief that time in the sauna brings a good night's sleep. Through a combination of temperature regulation, stress reduction and muscle relaxation, sauna bathing creates the optimal physiological and mental conditions for deep, restorative sleep. By incorporating regular sauna visits into your evening routine, you can naturally and effectively improve your sleep quality and, with it, your overall wellbeing.
Sources with links
[1] Hussain, J. N., Greaves, R. F., & Cohen, M. M. (2019). A hot topic for health: Results of the Global Sauna Survey. Complementary Therapies in Medicine, 44, 223-234. https://pubmed.ncbi.nlm.nih.gov/31126560/
[2] Okamoto-Mizuno, K., & Mizuno, K. (2012). Effects of thermal environment on sleep and circadian rhythm. Journal of Physiological Anthropology, 31(1), 14. https://pmc.ncbi.nlm.nih.gov/articles/PMC3427038/
[3] Haghayegh, S., Khoshnevis, S., Smolensky, M. H., Diller, K. R., & Castriotta, R. J. (2019). Before-bedtime passive body heating by warm shower or bath to improve sleep: A systematic review and meta-analysis. Sleep Medicine Reviews, 46, 124-135. https://pubmed.ncbi.nlm.nih.gov/31102877/
