Direct answer
Regular Finnish-style sauna is a reasonable habit for a healthy adult who already likes heat. It is not a drug. It is not a replacement for walking, lifting or sleep. It has not been shown to prevent heart disease, dementia or early death.
The paper most often quoted — Laukkanen and colleagues in JAMA Internal Medicine, 2015 — is an observational study of middle-aged Finnish men who already used a sauna. More frequent bathing was associated with lower rates of some fatal cardiovascular outcomes over about twenty years. Association is not proof that heat caused the difference.
A small eight-week randomised trial (Lee, 2022) found that adding a short sauna after guideline-based exercise was associated with a further drop in systolic blood pressure compared with exercise alone. The sauna sat on top of training, not instead of it.
Large, long randomised trials of sauna as a health intervention are still missing. Dr Heather Massey said so on BBC News in December 2025 and again on The Guardian’s Science Weekly in April and July 2026.
Key facts
- A traditional Finnish sauna is a hot, relatively dry room, typically around 80–100°C, with water thrown on stones for löyly. Sessions of five to twenty minutes, a few times a week, are ordinary in Finland — a culture, not a medical protocol.
- Laukkanen et al., 2015 (not 2018): 2,315 middle-aged men from eastern Finland; median follow-up 20.7 years. More frequent sauna use was associated with lower sudden cardiac death, fatal coronary heart disease, fatal cardiovascular disease, and all-cause mortality after adjustment. The sample was men. There were almost no non-users. There was no randomised assignment.
- Mayo Clinic Proceedings, 2018: regular Finnish sauna bathing may be linked with lower risk of some vascular outcomes. Most long-term outcome data were still observational. Randomised trials were few and small.
- Lee et al., 2022: 47 sedentary adults, eight weeks. Exercise plus a 15-minute post-exercise sauna, three times a week, was associated with a further mean 8.0 mmHg drop in systolic blood pressure versus exercise alone (95% CI −14.6 to −1.4). Small trial. Short. Adjunct, not replacement.
- Massey, University of Portsmouth: there is not “the sort of gold standard data from large randomized controlled trials that we’d really like to see.”
- Two or three sessions a week is a reasonable habit for a healthy adult who already likes it. That figure is not a medical dose.
- In a UK garden, whether the room still holds heat in January is a construction question: 100 mm SIP walls, floor and ceiling. That is insulation, not a health claim.
Evidence at a glance
| Question | What the evidence actually is | Evidence level |
|---|---|---|
| Does frequent sauna use prevent cardiovascular death? | In Finnish observational follow-up of middle-aged men, more frequent traditional sauna bathing was associated with lower fatal cardiovascular rates. Not a randomised trial. Not women. Not a UK cohort. | Observational |
| Does sauna replace aerobic exercise? | Lee 2022 added a short sauna after guideline-based training. Exercise alone still improved fitness against control. | Small randomised trial (adjunct) |
| Are large trials of sauna as a health intervention available? | Massey (BBC, Dec 2025; Guardian Science Weekly, Apr and 30 Jul 2026): gold-standard large RCTs are not there yet. | Expert advice |
| Mayo 2018 — did it settle the question? | Narrative review: regular Finnish sauna may be linked with some vascular outcomes; uncertainty flagged; more work needed. | Expert advice (narrative review) |
| Sleep, mood, “immune protection,” calorie burn as a jog equivalent | Mechanisms are postulated; much of the consumer copy overstates them. Not established as disease prevention or exercise replacement. | Expert advice / limited trials |
What a Finnish sauna actually is
A traditional Finnish sauna is a hot, relatively dry room, typically around 80–100°C, with water thrown on stones for löyly — a burst of steam. The Finnish Sauna Society has promoted that culture since 1937. Unesco has listed Finnish sauna culture as intangible heritage.
That matters for how we read the science. Almost everyone in the long Finnish studies already uses a sauna. Researchers are usually comparing people who go often with people who go less often — not people who never go at all.
Wellness One builds traditional heat rooms for UK gardens, with 100 mm SIP insulation on walls, floor and ceiling so the room can still be used in January. That is a climate and construction choice. It does not turn the session into a medicine.
The study everyone quotes: Laukkanen, 2015
The paper that still sits under most “sauna is good for your heart” claims is an observational cohort, not a trial.
In 2015, Jari Laukkanen and colleagues published in JAMA Internal Medicine on 2,315 middle-aged men from eastern Finland, drawn from the Kuopio Ischemic Heart Disease Risk Factor Study. Baseline examinations ran from 1984 to 1989. Median follow-up was 20.7 years. Men were grouped by how often they reported sauna bathing at the start: once a week, two to three times, or four to seven times.
After adjustment for a long list of cardiovascular risk factors, more frequent sauna use was associated with lower rates of sudden cardiac death, fatal coronary heart disease, fatal cardiovascular disease, and all-cause mortality. Longer sessions were also associated with lower sudden-cardiac-death rates.
A 2018 paper in the same research line is a review, not the original 20-year follow-up.
This is serious epidemiology. It is also, still, a photograph of Finnish men who already sauna, already live in a sauna culture, and who may differ in ways no questionnaire fully captures. There was no randomised assignment. There were almost no non-users. The sample was men.
We will not recast it as a prescription.
What the 2018 Mayo review actually reviewed
In August 2018, Laukkanen, Tanjaniina Laukkanen and Setor Kunutsor summarised the evidence in Mayo Clinic Proceedings. They wrote that regular Finnish sauna bathing may be linked with lower risk of some vascular outcomes, and they set out postulated mechanisms. They also flagged uncertainty. Most of the long-term outcome data were still observational. Randomised trials were few and small.
That review is often cited as if it settled the question. It did not. It organised what existed and said, politely, that more work was needed.
The small trial that actually randomised people: Lee, 2022
The trial people mean when they talk about blood pressure is Earric Lee and colleagues, 2022, in the American Journal of Physiology. Forty-seven sedentary adults, mean age 49, with at least one traditional cardiovascular risk factor, were randomised for eight weeks to guideline-based exercise plus a 15-minute post-exercise sauna three times a week; to the same exercise without sauna; or to a control group.
Exercise alone improved fitness against control. Adding the sauna was associated with a further mean reduction in systolic blood pressure of 8.0 mmHg compared with exercise alone (95% CI −14.6 to −1.4).
Read that slowly. It is a small randomised trial. Eight weeks. Forty-seven people. The sauna sat on top of exercise, not instead of it. Sauna is an adjunct. It is not a replacement for walking, lifting, or sleep.
What Massey has been saying in public
On 30 July 2026, The Guardian’s Science Weekly podcast re-aired a conversation that had first gone out on 2 April. Madeleine Finlay sat with Ian Sample and Dr Heather Massey, associate professor at the University of Portsmouth’s Extreme Environments Laboratory.
Massey’s answer was not a sales line. There is not, she said, “the sort of gold standard data from large randomized controlled trials that we’d really like to see” for health benefits of saunas or cold-water immersion.
On 30 December 2025 she told BBC News: “There are a lot of people who swear by hot and cold exposure, but we don’t yet have sufficient evidence to say it’s categorically good for you.” And: “We’ve never really done a proper sauna trial. I suspect we’ll find benefits in the future, but we’re not there yet.”
She advises easing in gradually, and speaking to a GP first if you have an underlying condition or are pregnant. Heat is a cardiovascular load. People have come to harm — rarely, and often with alcohol or existing disease in the picture.
None of that makes sauna reckless for a healthy adult who builds up slowly, stays hydrated, and leaves alcohol outside the door. It does make “clinically proven longevity protocol” a phrase we will not use.
Recovery, sleep, mood, immune claims — what we will not stretch
Heat can make muscles feel looser. Many people sleep well after a session, perhaps because core temperature rises and then falls. Many people feel calmer. Those are ordinary human reports. They are not the same as “shown to increase white blood cells and prevent colds,” and they are not a reason to print 50% fewer infections as a fact.
If you want heat as a recovery tool after sport, treat it as one tool among several, and do not use it as a licence to train harder than you should.
A reasonable habit, not a drug
A fair reading of the evidence, as of 26 August 2026:
- In Finnish observational studies of middle-aged men, more frequent traditional sauna bathing has been associated with lower rates of some fatal cardiovascular outcomes over decades. That is a signal, not a prescription.
- A small eight-week randomised trial found that adding short post-exercise sauna sessions to training was associated with a further drop in systolic blood pressure compared with exercise alone.
- Large, long randomised trials of sauna as a health intervention are still missing. Massey said so on the BBC in December 2025 and again on Science Weekly in April and July 2026.
- Enjoyment, ritual, and the social pause may be doing as much work as the thermometer.
Two or three sessions a week is a reasonable habit for a healthy adult who already likes it. Four to seven times a week was a reporting group in the Finnish cohort, not a dose we will sell.
If you want the habit to survive a UK winter, the unglamorous variable is whether the room still holds heat when it is 2°C and raining. 100 mm SIP walls, floor and ceiling are how a properly insulated outdoor sauna is built for this climate. That is construction. It is not evidence that insulation prevents heart disease.
Commercial “best garden sauna” round-ups exist. Treat pieces like that as paid or commercially positioned ranking, not as independent clinical evidence.
The evidence, such as it is, is about a hot room used often, without drama, as part of a life that already includes movement and sleep. That is a ritual worth protecting. It is not a drug.
A working pattern (healthy adults who already like it)
This is a starting pattern, not a prescription.
- Heat: about 8–15 minutes, around 80–90°C to begin with. Leave sooner if you feel light-headed, sick or not yourself.
- Sit, breathe, throw a little water on the stones if you want löyly.
- Cool in air or a lukewarm shower. Cold water is a separate load — see a GP first if you have heart or blood-pressure issues, and do not plunge alone.
- Two or three sessions a week is plenty for a habit. Daily use is not a proven “more is better” protocol.
- Water in. Alcohol out. Eat before you are empty, not immediately after a heavy meal.
Beginners can start cooler and shorter (70–80°C, five to ten minutes) and build up.
Who should see a GP
Speak to your GP before you heat the room if any of the following apply. This is not a complete list.
- Heart disease, a recent heart attack, arrhythmia, or unstable or untreated high blood pressure
- You are pregnant, or think you might be. NHS-style wording still reproduced on GP practice sites in 2026: there is little research; people may choose to avoid saunas, jacuzzis and steam rooms because of overheating, dehydration and fainting; a significant rise in core temperature could be harmful, particularly in the first 12 weeks.
- You take medicines that affect heart rate, blood pressure or fluid balance
- You have epilepsy, or you faint easily
- You are unsure
Children under three should not be in a hot sauna. Older children need an adult, a cooler bench, and a short stay.
Do not use a sauna after alcohol. Heat plus alcohol is how ordinary sessions turn into emergency ones.
This page is not medical advice.
What we are not claiming
We are not claiming that sauna prevents heart disease, dementia, stroke, cancer or early death. We are not claiming that Laukkanen 2015 proves causation. We are not claiming that Lee 2022 generalises beyond a small, short trial in people who were also exercising. We are not claiming sauna replaces exercise, “detoxes” the body, or is safe in pregnancy. We are not printing 50% or 40% mortality reductions as proven facts. We are not offering medical advice.
Frequently asked questions
What does the evidence actually say about sauna and heart health?
In an observational study of 2,315 middle-aged Finnish men (Laukkanen et al., JAMA Internal Medicine, 2015), more frequent traditional sauna bathing was associated with lower fatal cardiovascular rates over about twenty years. That is not a randomised trial, not a UK sample, and not proof that sauna prevents heart disease. The 2018 Mayo review said regular Finnish sauna may be linked with some vascular outcomes and asked for better trials.
How often should you use a sauna?
Two or three sessions a week is a reasonable habit for a healthy adult who already likes it. Four to seven times a week was a group in the Finnish cohort, not a medical dose. Start shorter and cooler if you are new to heat.
Does sauna replace exercise?
No. Lee 2022 added a 15-minute sauna after exercise. The training still did the fitness work. Use sauna as a habit alongside movement and sleep, not instead of them.
Is sauna use “clinically proven”?
Not in the sense people mean when they say that. Large randomised trials are still missing (Massey, BBC 30 Dec 2025; Guardian Science Weekly 30 Jul 2026). Observational findings and one small blood-pressure trial are not a licence to call sauna a treatment.
Is this medical advice?
No. If you have heart disease, unstable blood pressure, are pregnant, or are unsure, speak to your GP before you heat the room.
References
- Laukkanen T, Khan H, Zaccardi F, Laukkanen JA. Association between sauna bathing and fatal cardiovascular and all-cause mortality events. JAMA Internal Medicine. 2015;175(4):542–548. https://doi.org/10.1001/jamainternmed.2014.8187
- Laukkanen JA, Laukkanen T, Kunutsor SK. Cardiovascular and other health benefits of sauna bathing: a review of the evidence. Mayo Clinic Proceedings. 2018;93(8):1111–1121. https://www.mayoclinicproceedings.org/article/S0025-6196(18)30275-1/fulltext — https://doi.org/10.1016/j.mayocp.2018.04.008
- Lee E, Kolunsarka I, Kostensalo J, et al. Effects of regular sauna bathing in conjunction with exercise on cardiovascular function: a multi-arm randomized controlled trial. American Journal of Physiology – Regulatory, Integrative and Comparative Physiology. 2022. https://doi.org/10.1152/ajpregu.00076.2022
- Massey H, interviewed by Finlay M and Sample I. Revisited: saunas, cold plunges — where does the evidence stand? The Guardian Science Weekly, 30 July 2026 (re-air of 2 April 2026). https://www.theguardian.com/science/audio/2026/jul/30/revisited-saunas-cold-plunges-where-does-evidence-stand-podcast
- Rufo Y. Saunas and cold plunges: what does the science say? BBC News, 30 December 2025. https://www.bbc.com/news/articles/c5yj3g0p26ro
- Syndicated NHS-style pregnancy wording (confirm live `nhs.uk` before publish): Collingwood Surgery. https://collingwoodsurgery.nhs.uk/collingwood/common-questions/pregnancyis-it-safe-to-use-a-sauna-or-jacuzzi-if-i-am-pregnant
By the Wellness One specialist team, Wellness One Healthstyle Ltd (Co. No. 14514433). Last updated 26 August 2026. This page is not medical advice.