Sauna benefits: what the evidence actually shows
This is the strongest evidence in the whole hot-and-cold category. It is also observational, it studied 2,315 Finnish men, and its comparison group was one sauna a week — not zero.
Last verified · Ice & Cedar editorial
We spend most of this site being sceptical, so let us start by conceding the point: the sauna literature is genuinely better than the cold plunge literature. There is a large prospective cohort with about twenty years of follow-up behind it. Cold has nothing comparable. Now here is what that cohort did and did not show.
Health information, not medical advice. Cleveland Clinic says to skip the sauna if you have recently had a heart attack or stroke, or if you have been drinking alcohol, and to check with a healthcare provider first if you are over 65 or under 16, pregnant or trying to conceive, have heart or neurologic conditions or high or low blood pressure, or take medications. Ask your doctor, not a gear site.
What the Finnish study found
The Kuopio study (Laukkanen et al., JAMA Internal Medicine, 2015) followed a “population-based sample of 2315 middle-aged (age range, 42-60 years) men from Eastern Finland”. It is a prospective cohort study — the researchers watched what men already did, over roughly two decades. Nobody was assigned to a sauna.
The headline numbers, for sudden cardiac death:
| Sauna frequency | Hazard ratio (SCD) | 95% CI |
|---|---|---|
| 1 session / week | reference | — |
| 2–3 sessions / week | 0.78 | 0.57–1.07 — crosses 1.0 |
| 4–7 sessions / week | 0.37 | 0.18–0.75 |
The authors’ own conclusion: “Increased frequency of sauna bathing is associated with a reduced risk of SCD, CHD, CVD, and all-cause mortality.” Note the verb. They also write that “further studies are warranted to establish the potential mechanism that links sauna bathing and cardiovascular health” — which is a research team saying, in print, that they have not shown why.
The caveat nobody carries with the headline
You have seen “saunas cut your risk of dying by 40%.” Look at the first row of that table again. The comparison group is one sauna a week. It is not zero.
This is a Finnish cohort, where sauna use is close to universal — there was no large never-used-a-sauna group to compare against. So the study cannot tell you what a sauna does versus no sauna. It tells you what moresauna is associated with, among men who all already use one. Every headline framed as “sauna users versus non-users” is describing a comparison that was never made.
And notice the middle row while you are here. At two to three sessions a week — which is what most people with a home sauna would realistically do — the confidence interval runs from 0.57 to 1.07. It crosses 1.0. That result is compatible with no effect at all. The dose that produced the famous number is four to seven sessions a week, which is close to a daily habit.
Association, and the argument about it
The obvious rival explanation is not exotic: a man who saunas five times a week is a man with the health, the leisure and the income to sauna five times a week. Sick men sauna less. That is called healthy-user confounding, and an observational study cannot rule it out — it can only adjust for the confounders it thought to measure.
This is not our objection. It was a live argument in the journal: a commentary titled “The Link Between Sauna Bathing and Mortality May Be Noncausal” was published in JAMA Internal Medicinein 2015, with a reply from the original authors. We link both below. We are not going to characterise arguments we could not read in full — the paywall is real — but the existence of a titled, published challenge is itself worth knowing.
How thin the trial evidence is
Beyond that one cohort, the field gets sparse fast. A systematic review of regular dry sauna bathing found that “only 13 studies were randomized controlled trials and most studies were small (n < 40)”, and that only three of the studies reviewed were assessed as having a low overall risk of bias.
That is the honest map of the territory: one good cohort that cannot prove causation, a handful of small trials, and an enormous volume of confident internet writing built on top of both.
What we think you should take from this
Do not buy a sauna because of a hazard ratio. Buy one if you will actually use it — the most consistent thing in the data is frequency, and frequency is a behaviour, not a purchase. A sauna you use four times a week is the thing that was studied. A sauna you use twice a month is a shed.
Which turns the useful questions into ones we can actually answer with arithmetic rather than epidemiology: what circuit it needs, what it costs to run, and whether the version you can afford to run is the version you would use often enough to matter. Those we can do, and we show our working.
Frequently asked questions
Does using a sauna actually reduce your risk of dying?
The honest answer is: it is associated with a lower risk in one long-running Finnish cohort, and association is not causation. The 2015 JAMA Internal Medicine study of 2,315 middle-aged Finnish men found that men who used a sauna 4-7 times a week had a hazard ratio of 0.37 for sudden cardiac death compared with men who used one once a week. The authors' own conclusion uses the word 'associated', and they add that 'further studies are warranted to establish the potential mechanism'. Nobody was randomised to a sauna. A man who saunas five times a week is also a man with the health, time and money to do so.
Is the sauna evidence better than the cold plunge evidence?
Yes, and it is worth saying plainly because we spend most of this site being sceptical. The sauna side has a large prospective cohort with a median follow-up of about 20 years behind it. The cold side does not have anything comparable. That is a real asymmetry — but 'better than the other observational literature' is a low bar, not a clean bill of health.
What does '40% lower risk' actually mean?
It is the single most misreported number in this category, and the error is in the comparison group. The Finnish hazard ratios are 4-7 sessions per week measured against ONE session per week — not against people who never use a sauna. In a Finnish cohort, sauna use is close to universal; there was no meaningful never-user group to compare against. So any headline of the form 'saunas cut your death risk versus not saunaing' is describing a comparison the study did not make.
How many high-quality trials are there?
Few, and small. A systematic review of regular dry sauna bathing found that 'only 13 studies were randomized controlled trials and most studies were small (n < 40)', and that only three of the reviewed studies were assessed as having a low overall risk of bias. That is the state of the field: one strong cohort, a thin trial literature, and a lot of confident blog posts.
Is it the heat, or is it the lifestyle?
Nobody has established that, and the study authors say so themselves. This is the central unresolved question, and it is serious enough that a commentary titled 'The Link Between Sauna Bathing and Mortality May Be Noncausal' was published in JAMA Internal Medicine alongside the original work. The mechanism is plausible — sustained heat raises heart rate in a way that resembles moderate exercise — but plausible is not demonstrated.
So should I buy one?
Not on the strength of a mortality claim we cannot stand behind. Buy one if you will use it — the observational data's most consistent signal is frequency, which is a behaviour, not a purchase. The useful questions are the ones we can answer with arithmetic: what circuit it needs, what it costs to run, and whether it fits. Those we do.
What are the actual risks?
Cleveland Clinic flags dehydration as a major one — 'thirst, headaches, muscle cramps and confusion' — and says to skip the sauna entirely if you have recently had a heart attack or stroke, or if you have been drinking alcohol. Check with a healthcare provider first if you are over 65 or under 16, pregnant or trying to conceive, have heart or neurologic conditions or high or low blood pressure, or take medications. The alcohol point is not a throwaway: the systematic review notes that half or more of sauna-associated deaths involve alcohol.
Related
Sources
- Laukkanen T, Khan H, Zaccardi F, Laukkanen JA. Association between sauna bathing and fatal cardiovascular and all-cause mortality events. JAMA Intern Med. 2015;175(4):542-8. — Source of the cohort description (2,315 middle-aged men, ages 42-60, Eastern Finland), the hazard ratios and confidence intervals in the table, the one-session-per-week reference group, and the authors' own 'associated with' conclusion. (accessed 2026-07-16)
- JAMA Internal Medicine — full article (Laukkanen et al., 2015) — Full text of the study above. (accessed 2026-07-16)
- Kivimäki M, Virtanen M, Ferrie JE. The Link Between Sauna Bathing and Mortality May Be Noncausal. JAMA Intern Med. 2015;175(10):1718. — A published commentary challenging the causal reading. We cite the title and citation only — the full text is paywalled and we have not read the argument, so we do not characterise it. (accessed 2026-07-16)
- Laukkanen T, Khan H, Zaccardi F. The Link Between Sauna Bathing and Mortality May Be Noncausal — Reply. JAMA Intern Med. 2015;175(10):1719-20. — The original authors' reply to the commentary above. Cited for completeness; also paywalled. (accessed 2026-07-16)
- Hussain J, Cohen M. Clinical Effects of Regular Dry Sauna Bathing: A Systematic Review. Evid Based Complement Alternat Med. 2018. — Source of "only 13 studies were randomized controlled trials and most studies were small (n < 40)", the low-risk-of-bias count, and the note that half or more of sauna-associated deaths involve alcohol. (accessed 2026-07-16)
- Cleveland Clinic — Sauna benefits — Source of the dehydration risk, the alcohol and recent heart attack/stroke exclusions, and the consult-your-provider list. (accessed 2026-07-16)