Sauna and Cardiovascular Health: Association Is Not Proof

Finnish cohort studies link four to seven sauna sessions a week with a 61% lower stroke rate and a 63% lower rate of sudden cardiac death. They are observational, and a randomized trial in heart patients found no vascular improvement.

Long-term Finnish studies report lower rates of stroke, cardiovascular death and high blood pressure among people who used a sauna most days of the week. The numbers are large, and the study design matters: these are observational cohorts that recorded people's existing habits, not trials that assigned anyone a sauna schedule. Where researchers have assigned sauna in a trial, the results are smaller and narrower.

What the stroke study found

A 2018 prospective cohort study from the Kuopio Ischemic Heart Disease study followed 1,628 Finnish men and women, ages 53 to 74, who had no known history of stroke. Over a median 14.9 years, 155 strokes occurred. Compared with people who reported one sauna session a week, those who reported four to seven had a 61% lower rate of stroke after adjustment for cardiovascular risk factors (hazard ratio 0.39). The figure barely moved after further adjustment for physical activity and socioeconomic status (0.38). The link was similar for ischemic stroke; with only 34 hemorrhagic strokes, the study could say little about them.

The result is an association. Sauna habits were reported once, at baseline. Participants were not randomly assigned, and frequent sauna users may differ in ways statistical adjustment cannot fully capture. The study does not show that adding sauna sessions will prevent a stroke, and it excluded people who had already had one.

What the mortality studies found

The 2015 Kuopio study followed 2,315 Finnish men aged 42 to 60 for a median 20.7 years. Compared with men who reported one session a week, men who reported four to seven had a 63% lower rate of sudden cardiac death (hazard ratio 0.37), with similar trends for fatal coronary heart disease, fatal cardiovascular disease and death from any cause. Session length followed the same pattern: men whose sessions lasted more than 19 minutes had a 52% lower rate of sudden cardiac death than men whose sessions lasted under 11 minutes (0.48). Only 201 of the 2,315 men were in the most frequent group, and the study included no women.

A 2018 analysis that added women followed 1,688 adults, 51% of them women, for a median 15 years. Four to seven sessions a week was linked to lower cardiovascular mortality (hazard ratio 0.23), but that estimate rests on 8 deaths in the most frequent group, and the association was not statistically significant in women analyzed on their own, largely because few women in the frequent-sauna groups died. In that cohort the typical session lasted about 13 minutes in a room averaging about 169°F.

The same cohort has linked four to seven sessions a week with a 47% lower rate of developing high blood pressure among 1,621 men who did not have it at baseline (hazard ratio 0.53 over a median 24.7 years). Outside Finland, a Japanese cohort of 30,076 adults aged 40 to 59 found a similar pattern for hot-tub bathing: people who bathed almost every day had a 28% lower rate of cardiovascular disease and a 26% lower rate of stroke than people who bathed two or fewer times a week, with no difference in sudden cardiac death.

What trials found when sauna was assigned

When researchers at the Montreal Heart Institute randomly assigned 41 adults with stable coronary artery disease to eight weeks of Finnish sauna (four sessions a week, 20 to 30 minutes at about 174°F) or to their usual routine, the sauna group adapted to the heat, with a lower resting core temperature and more sweating. Flow-mediated dilation, arterial stiffness and blood pressure changed no more than in the control group.

In a 2022 Finnish trial , 47 inactive adults with at least one cardiovascular risk factor were assigned to exercise, exercise followed by a 15-minute sauna, or no change for eight weeks. Adding the sauna lowered systolic blood pressure by 8 mmHg more than exercise alone and raised fitness slightly more. The sauna was always paired with exercise, and the trial was small and short.

Frequent sauna also does not cancel out high blood pressure. Among Kuopio men followed for a median 27.8 years , those with systolic pressure of 140 mmHg or higher still had a higher rate of cardiovascular death than men with normal pressure, even when they used the sauna three to seven times a week (hazard ratio 1.52). None of these studies makes sauna a replacement for blood-pressure care, cholesterol treatment, exercise, sleep, smoking cessation, or other medical advice. Much of the evidence comes from Finnish populations accustomed to traditional sauna, so it should not be generalized to every heat device or every patient.

What happens during one session

Sauna increases heat load, skin blood flow, sweating, and heart rate . Blood pressure can move in both directions. In a study of 19 healthy adults , blood pressure and heart rate rose steadily during 25 minutes at 199°F, a cardiac load the authors compared to cycling at 60 to 100 watts, then fell below the starting level during recovery. In a study of 102 adults with at least one cardiovascular risk factor , average systolic pressure was lower right after 30 minutes at 163°F (137 to 130 mmHg) and arterial stiffness fell. A session is a cardiovascular stressor, not a home blood-pressure treatment.

Who should be careful

A review in the American Journal of Medicine lists unstable angina, a recent heart attack and severe aortic stenosis as reasons not to use a sauna, and describes sauna as safe for most people with stable angina or an old heart attack. Alcohol is the risk that shows up most: half of the people who died in Finnish saunas from 1990 to 2002 were under the influence of alcohol , and in a trial of 10 healthy men , sauna after heavy drinking dropped systolic pressure from 136 to 113 mmHg while sauna alone did not.

Leave immediately for chest pain, faintness, unusual shortness of breath, confusion, severe headache, or weakness. Skip alcohol, arrive hydrated, and cool down before standing or driving. Ask your clinician before sauna if you have heart disease, poorly controlled blood pressure, a fainting history, are pregnant, or take medicine that changes sweating, heat tolerance, or blood pressure.

For the room conditions used in many studies, see our sauna temperature guide . It explains why study temperatures are not a prescription.

SaunaShare is a JavaScript application. Enable JavaScript for the full experience, or use the links below to browse the directory.