Sauna Extends Life by Decades: Scientists Question a Popular Myth

Regular sauna use has long been associated with a substantial reduction in the risk of heart disease, dementia, and premature death. However, new scientific data suggest the benefits of high temperatures may have been overestimated, and that people who visit saunas frequently may simply be healthier to begin with.

This is reported by Xataka.

Saunas are increasingly becoming part of a healthy lifestyle. They are offered not only by specialized wellness centers but also by ordinary gyms expanding their list of services.

The popularity of saunas is largely linked to scientific studies that for years pointed to their possible positive effects on the heart, blood vessels, and lifespan. However, researchers have pointed out a significant problem in interpreting such results.

Most of the striking figures about sauna benefits come from the Finnish KIHD study. Within it, scientists followed the health of 2315 men aged 42 to 60 for more than two decades.

The results were extremely convincing at first glance. Among men who used the sauna four to seven times a week, the risk of sudden cardiac death was 63% lower than among those who went only once a week.

Other studies also found associations between regular sauna use and lower risk of certain diseases. In particular, a reduction in dementia risk by 65%, stroke by 61%, and hypertension by 47% was reported.

These figures became the basis for the notion that the sauna might be one of the simplest ways to extend life. However, such results do not prove that exposure to high temperatures itself protects against disease.

The main problem lies in a phenomenon scientists call reverse causation. It occurs when cause and effect are mistakenly swapped.

In the case of the sauna, another explanation of the statistics is possible. Frequent sauna visits do not necessarily make people healthier — it is quite likely that people who are already healthier are able to regularly tolerate high temperatures.

Being in a room heated to 80°C places a significant strain on the body. The cardiovascular system has to work harder to help cool the body.

A person with early heart failure or other health problems may feel discomfort during such procedures. As a result, they are likely to visit the sauna less often or avoid it altogether.

Accordingly, among people who go to the sauna four to seven times a week there may be more individuals who were healthier to begin with. This characteristic can influence the results of long-term observations.

To test the direct effect of saunas on the body, scientists began using clinical trials. Unlike observational studies, trials allow more precise assessment of changes related to a specific procedure.

In 2022 researchers conducted a small experiment involving 47 adults leading sedentary lifestyles. Participants combined physical exercise with 15-minute sauna sessions.

Results showed that adding a sauna after training helped lower elevated blood pressure by an additional 8 mmHg compared with exercise alone. At the same time, researchers did not find a similar positive effect on heart rate variability.

Another trial took place in 2023 at the Montreal Heart Institute. It involved 41 patient with stable ischemic heart disease.

For two months participants visited the sauna four times a week at 79°C. However, after the experiment researchers did not record improvements in endothelial function, reductions in arterial stiffness, or decreases in blood pressure.

Despite mixed results, sauna exposure does produce certain physiological changes. Under high temperature, blood vessels dilate and the heart begins to pump more blood.

This mechanism helps the body shed excess heat. In terms of cardiovascular load, it partially resembles low- or moderate-intensity physical exercise.

Some studies also point to a possible short-term effect of saunas on the immune system. In particular, one 30-minute session can cause temporary mobilization of immune cells.

However, this does not mean that regular sauna use necessarily strengthens immunity or prevents disease. The observed changes mainly concern the short-term response of the body to heat stress.

Besides potential benefits, researchers have found adverse effects of frequent exposure to high temperatures. In particular, prolonged heating can affect male reproductive function.

In one experiment healthy volunteers visited the sauna twice a week for three months. Afterwards scientists recorded a decrease in sperm count and worsening of sperm motility.

At the same time, the observed changes were not permanent. After several months without sauna use, sperm parameters recovered.