What does the research say about saunas and your health?

01

These are the studies behind the health claims

Each row is a study we cite below, with the people it followed and what kind of study it was. Most are observational, which means the researchers recorded people's habits and counted who got sick, and three are trials that assigned the heat.

02

Most of the evidence comes from one study in Kuopio

Most of the big sauna findings we read trace back to the Kuopio Ischemic Heart Disease Risk Factor Study. It recruited middle-aged men around Kuopio in eastern Finland in the 1980s, asked how often they took a sauna, and followed them for two decades and more. A later wave added older adults, about half of them women.

In its best-known paper, men who took a sauna four to seven times a week had about a third the risk of sudden cardiac death of men who went once a week, after allowing for other heart risk factors. About half the once-a-week men had died of some cause by the end of follow-up, against just under a third of the most frequent bathers. Men who usually stayed in for more than 19 minutes also had a lower risk of sudden cardiac death than men who left before 11.

03

The same Finnish data tie frequent sauna to several other diseases

The Kuopio researchers went on to publish papers on dementia, high blood pressure, stroke and pneumonia, and each found lower risk among the people who took a sauna most days. The stroke paper and a later one on heart deaths drew on the older group with women in it, and the pattern held for both sexes.

The pneumonia result shows how these numbers move. Frequent bathers had close to half the risk at first. Once the researchers allowed for diet, social standing, exercise and inflammation, the gap shrank to one that sat right at the edge of chance. Read the table's percentages as a pattern in one population of Finns.

04

These studies can't show that the sauna caused the difference

Every Kuopio paper is observational. People chose how often they bathed, the researchers asked once at the start, and then they counted who got sick over the years. Men well enough to take a sauna most days may have been healthier in ways the questionnaires missed, and adjusting for the risk factors you measured can't account for the ones you didn't.

None of these studies can tell you that taking a sauna lowered anyone's risk. One research group, led by Jari Laukkanen at the University of Eastern Finland, wrote most of the papers, and its own review in Mayo Clinic Proceedings30275-1/fulltext) sets out the uncertainties that remain.

05

Fit men who also took saunas did best

One Kuopio paper measured fitness in an exercise test alongside sauna habits. Fit men who bathed three or more times a week had the lowest risk of sudden cardiac death, around a third that of unfit men who rarely bathed. Unfit men who bathed often came out only a little ahead of unfit men who didn't, and that gap wasn't statistically clear.

We'd read it as a reason to keep training and add the sauna on top.

06

A single hot session works your heart a little

In a University of Iowa lab, 25 young adults sat for half an hour in a chamber heated to 73°C (163°F). Their core temperature rose almost a degree and their heart rates climbed steadily while their blood pressure fell. Their blood also carried more of a heat shock protein, one of the ways cells cope with stress, and the authors note that exercise sets off some of the same responses.

The Kuopio researchers point to changes like these as a likely link to the heart findings. The same strain is why some heart patients should ask their doctor first.

07

Infrared cabins have far less evidence behind them

The Kuopio studies followed people who used traditional Finnish saunas, so their results don't carry over to an infrared cabin, which runs cooler. The best Canadian summary we found is a review in Canadian Family Physician by Richard Beever of BC's Northern Health. He found nine relevant studies and judged the evidence limited but moderate for blood pressure and heart failure. Single studies offered fair support on chronic pain and weak support on fatigue and weight, and fair, consistent evidence refuted claims that infrared lowers cholesterol. Beever also noted that makers claimed many more benefits than the published evidence could support.

A larger trial since then comes from Japan, where doctors use a far-infrared treatment called Waon therapy. Patients in hospital with advanced heart failure took a short daily session at 60°C (140°F) and rested under a blanket afterwards for ten days. They improved on symptoms and walking distance, though the blood marker the trial chose as its main measure didn't move by a significant margin. Those were supervised hospital patients, and the trial says little about a cabin at home.

08

Six runners got faster in a three-week trial

In New Zealand, six male distance runners sat in a hot, humid sauna for about half an hour after training, a dozen or so times over three weeks. Compared with three weeks without it, they ran about a third longer before exhaustion, which the authors equate to roughly 2% in a race. Their plasma volume rose as well, which the authors give as the likely reason.

Six runners make a tiny sample, and we wouldn't plan a season around it.

09

Cold plunges have the least research of all

Danish researchers compared eight young men who swim in winter00266-4) and use a sauna two or three times a week with eight similar men who don't. In the cold, the swimmers' bodies produced more heat, and the researchers saw signs of adaptation to both heat and cold. They also wrote that their design can't show winter swimming caused the difference.

A study this small describes how a body adapts. We found no long-term study of home cold plunges to set beside the Kuopio work, so a health claim about a plunge runs ahead of the evidence.

10

Ask your doctor first if you have heart trouble

A review in The American Journal of Medicine00671-9/fulltext) concluded that most healthy adults and children handle a sauna without trouble. It named unstable angina, a recent heart attack and severe aortic stenosis as reasons to stay out, and found sauna safe for most people with stable heart disease. Its firmest warning is about drinking, since alcohol in the sauna raises the risk of dangerously low blood pressure, an irregular heartbeat and sudden death.

The same review called sauna safe in an uncomplicated pregnancy. A later systematic review found one small study in which men's sperm production dropped with regular sauna use and recovered once they stopped. If you're pregnant or living with a heart condition, ask your doctor how hot and how long suits you.

11

Buy the sauna you'll use most days

If health is part of why you're buying, the Finnish data point to frequency. The lower risks showed up in people who bathed four or more times a week in a hot, traditional room, so a sauna close to the back door that you'll fire up on a Tuesday night in January does more for you than a grander one at the far end of the lot. Our running-cost calculator prices four sessions a week at your province's electricity rate, and our barrel guide compares the Canadian barrels we list.

If you'd pick an infrared cabin for convenience or a gentler heat, those are good reasons. The heart research above comes from hot traditional rooms, so it doesn't follow you into the cabin.

12

How did we read the research?

We read the published abstract of each study in the table on PubMed on Oct 11, 2026, and the full text of the winter-swimming study, which is free to read. The percentages are our conversions of each paper's hazard ratios after its adjustment for other risk factors, and they compare the most frequent bathers with people who took one sauna a week or fewer. We didn't interview the researchers, and nothing here replaces advice from your own doctor.