As the UK enters the darker months, many people are experiencing disrupted sleep. Shorter days, cold temperatures and end-of-year stress can all interfere with the body’s natural rhythm. New research suggests that sauna bathing may offer relief.
Single sauna session could increase deep sleep by 70%
A study published in Sauna Studies by Putkonen and Elomaa monitored sleep after a 30-minute sauna session at typical Finnish temperatures. Although only five participants were involved, the findings were significant. Deep sleep increased by about 70% within the first two hours of rest and by 45% over six hours. Participants also stayed awake for less time during the night.
The results fit with broader evidence showing that heat therapy can enhance slow-wave sleep, which supports physical recovery and cognitive function.
“While the research on sauna and sleep is still limited, the early findings are incredibly promising,” says Jake Newport, CEO of Finnmark Sauna. “That 70% increase in deep sleep came from a small group, but it supports what we hear from our own customers. They often tell us they fall asleep faster and wake up feeling more refreshed after regular sauna sessions.”
Survey shows 83% of regular sauna users sleep better
Jake adds, “It also aligns with findings from the Global Sauna Survey, which revealed that 83% of regular sauna users reported better sleep quality, with many saying they saw improvements in their sleep for 1–2 days after a sauna session.”
The 2019 Global Sauna Survey, published in Complementary Therapies in Medicine, gathered responses from more than 480 participants in Finland, Australia and the US. It found that relaxation and stress reduction were key motivations for sauna use, and that many users reported sustained improvements in restfulness. The results suggest sauna bathing may be a useful non-pharmacological option for people experiencing insomnia.
How sauna heat supports rest and recovery
When entering a sauna, the body undergoes a series of physiological changes. Endorphins and serotonin increase, promoting relaxation and emotional stability, while cortisol decreases, reducing stress.
Scientific reviews, including a 2023 study in Psychoneuroendocrinology, show that heat stress can raise beta-endorphins to three times baseline levels, a response similar to moderate exercise. Serotonin, which supports sleep onset, also rises. As cortisol drops, the nervous system calms and muscles relax.
The cooling period that follows a sauna is equally important. As core temperature falls, it mirrors the body’s natural preparation for sleep and helps support deeper rest.
Why sauna may help during winter
Winter affects hormone balance, energy and mood. Reduced daylight lowers serotonin, while darker evenings stimulate melatonin. This can cause fatigue during the day and restlessness at night.
In the UK, the NHS estimates that seasonal affective disorder affects around two million people each year, with symptoms intensifying in winter. Low serotonin contributes to low mood, while high melatonin can disrupt circadian cues. A 2023 NHS report states that one in three Britons experiences poorer sleep in colder months.
“The winter months can be hard on both body and mind,” says Jake. “We move less, stress more and spend far too much time indoors. A sauna session can help break that cycle. The heat improves circulation, eases tension and gives the body a cue to slow down, helping you relax and sleep better when you need it most.”
Studies from Finnish cohorts also suggest that regular sauna use may lower risks of winter-related issues such as hypertension and respiratory infections.
6 sauna habits to improve sleep this winter
Making sauna time part of an evening routine can help the body prepare for rest. These practices can enhance the effects.
- Make it an afternoon or evening ritual. Finish your session a few hours before bed to allow for a natural temperature drop that supports sleep onset.
- Focus on breathing. Slow, deep breaths stabilise the nervous system and prepare the body for rest.
- Stretch gently. Light stretching in the warmth helps relieve tension and supports relaxation.
- Use contrast therapy. After the sauna, step into cooler air or take a brief cold shower to reinforce the calming effect.
- Build a wind-down routine. Pair the sauna with quiet activities such as stretching, reading or journaling.
- Be consistent. Regular sauna use helps regulate the sleep cycle and manage stress.
“Good sleep isn’t restricted by what happens in bed, it actually starts with how you unwind,” says Jake. “A sauna session helps the body transition from high alert to deep rest. That shift in temperature and mindset is what makes the difference during the darker months.”