The Finnish Sauna Study Everyone Quotes Is Real, and It Is Weaker Than the Wellness Industry Wants It to Be
Men who used a sauna four to seven times a week had far fewer sudden cardiac deaths over twenty years than men who went once. That finding launched an industry. What the study can and cannot support, and who should be careful.
Sunday, September 6, 2026/4 min read
Every sauna brochure, infrared cabin advert and longevity podcast eventually cites the same paper: a Finnish study showing that frequent sauna use is associated with a large reduction in cardiovascular death. The paper exists, it was published in a serious journal, and its findings are roughly as reported. Whether they mean what the brochures say is a different question.
The study
The Kuopio Ischaemic Heart Disease Risk Factor Study enrolled 2,315 men aged 42 to 60 from eastern Finland between 1984 and 1989 and asked them, among many other things, how often they used a sauna and for how long. Tanjaniina and Jari Laukkanen and colleagues then followed them for a median of nearly twenty-one years and published the mortality results in JAMA Internal Medicine in 2015.
The raw numbers are striking. Among men who used a sauna once a week, 10.1 per cent died a sudden cardiac death over the follow-up. Among those who went two or three times a week it was 7.8 per cent, and among those who went four to seven times a week it was 5.0 per cent. All-cause mortality followed the same pattern: 49.1 per cent, 37.8 per cent and 30.8 per cent. After adjustment for cardiovascular risk factors, the men in the most frequent group had a hazard ratio for sudden cardiac death of 0.37 compared with the once-a-week men, which is to say roughly a third of the risk. Longer sessions, over nineteen minutes, were also associated with fewer sudden cardiac deaths than sessions under eleven.
It is a good study, from a well-run cohort, and the associations held up to the adjustments the authors could make.
Why it is not proof
It is observational, and the direction of causation is the whole problem. Men who feel well go to the sauna more often. Men with early heart failure, undiagnosed angina or chronic illness find a hot room at ninety degrees unpleasant and go less. Some of what looks like the sauna protecting the heart is the heart's condition deciding how often a man sits in the sauna. The authors acknowledged this. The adjustments reduce the problem but cannot remove it, because the things that make a man avoid the sauna are not all measured.
There is also the question of what sauna use is a marker for in a Finnish town in the 1980s. It is a social activity. Frequent users may have had more friends, more leisure, more money, a lakeside cottage. Each of those predicts a longer life independently. A single letter in the same journal made exactly this point under the title that the link may be non-causal, and nothing since has settled it.
Finally, it is a study of middle-aged Finnish men using a traditional Finnish sauna: a dry room at 80 to 100 degrees Celsius with periodic steam from water on the stones, sessions of ten to twenty minutes, often followed by a cold plunge or a walk outside. That is a specific practice. An infrared cabin at fifty degrees, a hotel steam room or a hot tub is not the same exposure, and the study says nothing about them.
What is plausible
There are mechanisms. A hot sauna raises heart rate to the level of moderate exercise, dilates blood vessels, lowers blood pressure for hours afterwards and improves measures of arterial stiffness in small trials. Repeated heat exposure is a mild stress the body adapts to. None of this is controversial, and it is consistent with a real, modest benefit. It is not consistent with the size of the effect in the raw numbers, which is why most cardiologists who have looked at the data assume the truth is somewhere between a small benefit and a large confounder.
Who should be careful
- Anyone with unstable angina, a recent heart attack or severe aortic stenosis. The heat is a cardiovascular load.
- Anyone who has been drinking. Alcohol and sauna together account for a large share of the sauna deaths that do occur in Finland.
- People on blood pressure medication who are prone to dizziness on standing; the drop in pressure on leaving the sauna can be steep.
- Pregnant women, for whom the guidance is to keep core temperature down and sessions short or skipped.
- Anyone dehydrated, which in a Gulf summer is a great many people by mid-afternoon.
For a healthy adult, a traditional sauna two or three times a week is pleasant, safe, and possibly good for the heart. That is a fair summary of the evidence, and it is less than a 63 per cent reduction in sudden death. The difference between those two sentences is the difference between a study and a sales pitch, a distinction our health desk has drawn before in the piece on what detox actually means and in the evidence review on zone 2 training. Sauna deserves the same treatment: a real finding, honestly sized.
Published in The Outspoken Digest
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Outspoken Digest Health DeskMedicine, public health and the research behind the headlines, read carefully.
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