In the Finnish Kuopio Ischemic Heart Disease Risk Factor Study, men who sat in a sauna four to seven times a week had a 63 percent lower risk of sudden cardiac death than men who went only once.
The findings, based on 2,315 middle-aged men tracked for a median of 20.7 years, were published in JAMA Internal Medicine in 2015 and remain one of the strongest datasets on the practice.
A 2025 narrative review in Cureus concludes that the cardiovascular changes triggered by frequent sauna sessions closely resemble those seen with moderate-intensity aerobic exercise.
The mechanism is heat stress. Sitting in a hot room raises core body temperature, expands blood vessels near the skin, and pushes the heart rate to between 100 and 150 beats per minute, according to UCLA Health.
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Repeated over weeks and months, that stress appears to train the cardiovascular system by lowering blood pressure, softening stiff arteries, and improving how much blood the heart moves per beat.
What the Finnish numbers show
The same Kuopio dataset tied other endpoints to frequent sauna use. Men who went four to seven times a week had a 50 percent lower risk of fatal cardiovascular disease and a 40 percent lower risk of death from any cause during follow-up.
Sessions longer than 19 minutes were linked to about half the sudden-death risk of sessions shorter than 11 minutes, the Cureus review notes.
The traditional Finnish saunas in the research were heated to roughly 158 to 212 degrees Fahrenheit and used for around 20 minutes at a time.
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Two to three sessions a week were also associated with meaningfully lower risks, but the biggest reductions turned up at four or more.
Earric Lee, a researcher at the Montreal Heart Institute quoted by Stanford Lifestyle Medicine, likens the effect to strength training, with heat and time acting as gradual stressors that improve blood vessel flexibility over months and years.
Evidence in women is still catching up
Most of the strongest data come from Finnish men. A 2018 cohort study in BMC Medicine of 1,688 middle-aged and older adults, of whom 51 percent were women who used a sauna regularly, showed a similar dose-response pattern.
Fatal cardiovascular events occurred at 2.7 per 1,000 person-years among those who bathed four to seven times a week, compared with 10.1 per 1,000 person-years among once-a-week users.
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The authors of the 2025 Cureus review caution that most sauna studies are observational and that randomized trials have produced "rather mixed conclusions," so a firm cause-and-effect link cannot yet be claimed.
Who should hold off
Recent heart attack and severe aortic stenosis, a narrowing of the heart's main valve, are listed as absolute contraindications in the Cureus review.
Alcohol before or during a session raises the risk of dangerous heart rhythms.
Anyone with a diagnosed heart condition should talk with their doctor before starting a regular sauna routine. The Cureus authors advise newcomers to begin with 10 to 15 minute sessions and build up gradually, keeping alcohol out of the routine.
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This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.