The Finnish Sauna Study Everyone Cites, and What It Can't Tell You

Sauna culture has spread well beyond Scandinavia. Gyms across Rhode Island now advertise infrared cabins, backyard barrel saunas have become a common home project, and contrast therapy studios pair hot rooms with cold plunges. The health claims attached to all of this usually trace back to a single study from eastern Finland.

That study is real, carefully done and genuinely interesting. It also answers a narrower question than most people assume.

What the Finnish researchers found

Researchers at the University of Eastern Finland drew on the Kuopio Ischemic Heart Disease Risk Factor Study, which enrolled men ages 42 to 60 between 1984 and 1989. In a 2015 paper in JAMA Internal Medicine¹, they analyzed 2,315 of those men, grouped by how often they used a sauna, and followed them for a median of about 20.7 years.

During that time there were 190 sudden cardiac deaths, 281 deaths from coronary heart disease, 407 cardiovascular deaths and 929 deaths from any cause.

The pattern was consistent. Compared with men who used a sauna once a week², those who went two to three times had a 22 percent lower risk of sudden cardiac death, and those who went four to seven times had a 63 percent lower risk. Death from cardiovascular disease was 27 and 50 percent lower in the same groups. Death from any cause was 24 and 40 percent lower.

Time mattered too. Sessions longer than about 19 minutes were linked with lower risk of fatal heart events than sessions under 11 minutes, though session length was not tied to overall mortality.

The authors adjusted for conventional risk factors such as blood pressure, cholesterol and smoking, and the associations held.

Why the comparison group matters

Here is the detail that rarely makes it into marketing copy. The study did not compare sauna users with people who never use a sauna. In Finland, sauna bathing is close to universal, and the lead investigator told NEJM Journal Watch⁴ that only 12 men in the cohort had no regular sauna use, too few to analyze.

So the finding is about dose among people who already use saunas. It says that in a population where nearly everyone goes once a week, going more often tracked with better outcomes. It does not directly say that an American who has never used a sauna will lower heart risk by starting.

The confounding problem

Observational studies can show associations but struggle to prove cause. Cardiologists commenting on the study raised the obvious alternative explanation. A man who can spend time in a sauna most days may have more leisure time, more money and less stress than one who cannot, and those factors independently predict better heart health.

Rita Redberg, the journal's editor, made a version of that point in an accompanying note, observing that it was impossible to say whether the benefit came from the heat, the relaxation, a life that allowed more leisure or the social time spent in the sauna.

There is also the question of who stays healthy enough to keep going. Men who were already developing heart problems might have cut back on sauna use, which would make frequent users look healthier for reasons unrelated to the heat itself.

Why heat could plausibly help

None of that means the association is meaningless. There are reasonable biological reasons to think heat exposure could benefit blood vessels. During a sauna session, skin blood flow rises sharply and heart rate climbs to levels similar to light or moderate exercise. Research summarized in Nature Reviews Cardiology³ notes that long-term sauna use has been linked with lower blood pressure and improvements in how blood vessels and the heart's main pumping chamber function.

Those are the same kinds of changes produced by regular exercise, which may explain part of the effect.

What the study did not cover

Every participant was a man. Women were not included, and the authors themselves called for studies in women and in people who are not lifelong sauna users.

The study also examined traditional Finnish saunas, which use dry heat around 80 to 100 degrees Celsius with water thrown on hot rocks. Infrared cabins run much cooler and heat the body differently. Steam rooms are humid. Results from one type do not automatically transfer to the others.

Using a sauna sensibly

For most healthy adults, a sauna is a low-risk habit. The Finnish researchers reported no harm from more frequent use in their cohort. Still, heat places real demands on the heart and circulation.

People with unstable chest pain, a recent heart attack, severe aortic stenosis or very low blood pressure should talk with a clinician first, and so should anyone on medications that cause dizziness on standing. Drinking water before and after helps, and alcohol should stay out of the sauna entirely, since it is a well-documented factor in sauna-related deaths. Stand up slowly when you finish.

If you enjoy the heat, the Finnish data give no reason to stop and some reason to think regular sessions fit well alongside aerobic fitness and sleep. If you are deciding whether to spend several thousand dollars on a home sauna specifically to prevent a heart attack, the evidence is not strong enough to carry that decision on its own.