Are saunas good for your heart? What the research shows

Sauna bathing has been a tradition in Finland for thousands of years, mainly for pleasure and relaxation, and it is becoming increasingly popular in many other populations. Research from Finland has linked regular sauna use with longer life, fewer deaths from heart disease and a lower risk of dementia.

The results are striking, but they come mostly from a single long-running study of middle-aged Finnish men. They show associations rather than proof that heat itself protects the heart, and trials that test saunas directly are few and small.

What a sauna does to the body

Sitting in a hot sauna raises body temperature and heart rate, and the body responds by sweating. MedlinePlus explains that your body normally cools itself by sweating, and that when heat overwhelms that system, body temperature can rise to dangerous levels.

Researchers have proposed several ways repeated heat might help the heart. A 2018 review in Mayo Clinic Proceedings notes that it has been postulated that regular sauna bathing may improve cardiovascular function. The suggested routes include better widening of blood vessels, less stiff arteries, changes in the nervous system’s control of the heart, improved blood fats and lower blood pressure. These are plausible mechanisms, not proven ones.

What the Finnish sauna study found

The best-known evidence, published in JAMA Internal Medicine in 2015, comes from the Kuopio Ischemic Heart Disease Risk Factor Study, which enrolled 2,315 men aged 42 to 60 in eastern Finland between 1984 and 1989. The men reported how often they used a sauna and for how long, and were then followed for a median of about 21 years.

Of the men, 601 used a sauna once a week, 1,513 two to three times a week and 201 four to seven times a week. Deaths from any cause occurred in 49.1% of the once-a-week group, 37.8% of the middle group and 30.8% of the most frequent users. Sudden cardiac deaths, when the heart stops without warning, followed the same pattern: 10.1%, 7.8% and 5.0%.

After accounting for other heart risk factors, men who used a sauna four to seven times a week had about 63% lower risk of sudden cardiac death than men who used it once a week. The authors concluded that increased frequency of sauna bathing is associated with a reduced risk of sudden cardiac death, fatal heart disease and death from any cause. Longer sessions, of more than 19 minutes, were also linked to fewer sudden cardiac deaths, but not to fewer deaths overall.

What the sauna research shows for dementia

The same men were tracked for dementia. Over about 20 years, 204 were diagnosed with dementia and 123 with Alzheimer’s disease. Men who used a sauna four to seven times a week had about a third of the dementia risk of once-a-week users; two to three sessions a week showed a smaller difference that could have been chance.

The authors concluded that in this male population, moderate to high frequency of sauna bathing was associated with lowered risks of dementia and Alzheimer’s disease, and called for studies of how that might happen.

The 2018 review brought together this and other work. It reports that emerging evidence links sauna bathing to lower risk of high blood pressure, heart disease and brain diseases, and to relief of conditions such as arthritis and headache. The review was written by members of the same research group, and much of the evidence it summarizes is observational.

What health sources say about sauna heat and safety

Government health information on heat focuses on safety. MedlinePlus lists older adults, young children, and people who are sick or overweight as most at risk of heat illness, and notes that taking certain medicines or drinking alcohol can also raise your risk.

Heat stroke, the most serious heat illness, is life-threatening: body temperature can climb above 106 F (41 C) in minutes. Its symptoms include dry skin, a rapid, strong pulse, dizziness, nausea and confusion.

Why the sauna findings are hard to interpret

The Finnish study was observational, so it cannot separate the sauna from the men who used it most. Frequent users may have been healthier, more relaxed or better off to begin with, and men who were already unwell may have avoided saunas, making the heat look protective.

Sauna habits were measured once, in the 1980s. The study included only men, all in Finland, where saunas are part of ordinary life. Only 201 men were in the most frequent group, so the biggest differences rest on relatively few deaths. And most of the headline findings come from a single cohort studied by one research team, which makes independent confirmation especially important.

What the sauna research cannot tell us yet

The studies do not show that starting to use a sauna would lower anyone’s risk of heart disease or dementia. They say little about women, about other types of heat bathing, or about people with existing heart conditions, for whom heat puts extra strain on the body. Trials that assign people to regular sauna use and follow them for heart events would be needed to test cause and effect.

What the sauna evidence adds up to

Frequent sauna use in Finnish men is consistently linked with fewer heart deaths, lower overall mortality and lower dementia risk, and there are plausible biological explanations. But the evidence rests largely on one observational study of men, from one research group, and cannot show that the heat is responsible.

Whether sauna use suits any one person depends on their health, their medicines and how their body handles heat.