Sauna researchers want harder evidence

Sauna is having a moment. Social sauna clubs are opening, and heat has become part of the longevity routine for a lot of people. The science hasn't kept up, and some of the researchers who study it say so openly.

In late September, about 15 of them met near Oslo for what NPR describes as the first International Heat Therapy Research Symposium. The goal was to agree on how to study heat properly and to set up a scientific body to steer the field. Heat therapy here covers Finnish sauna, infrared, hot water immersion and similar practices.

What the evidence says so far

Much of the interest goes back to Finland. In 2015, a team at the University of Eastern Finland published a study in JAMA Internal Medicine that followed 2,315 middle-aged men for a median of about 21 years. After adjusting for cardiovascular risk factors, men who used a sauna four to seven times a week had a lower risk of sudden cardiac death than men who went once a week. Fatal heart disease and death from any cause followed the same pattern.

That study was observational. It relied on what the men reported at the start, and other differences between frequent and occasional sauna users could explain part of the gap. The authors called for more studies to find a mechanism.

Controlled trials are rare. One of the few, published in 2022 by Earric Lee and colleagues, randomized 47 sedentary adults with at least one cardiovascular risk factor. For eight weeks, one group exercised, one group exercised and then sat in a sauna for 15 minutes, and one group changed nothing. Compared with exercise alone, the exercise and sauna group had a larger gain in cardiorespiratory fitness, lower systolic blood pressure and lower total cholesterol. It was a small trial, and its authors said the right dose and frequency are still unknown.

Why the field wants standards

The researchers NPR spoke to were candid about the gaps. Studies are small, methods vary a lot and key measurements are sometimes missing. Lee, now a postdoctoral researcher at the Montreal Heart Institute, is leading the effort to agree on standards first, including how to measure humidity and body temperature and how to define heat therapy at all.

Only then, he says, can the field run the larger multisite trials that would answer the basic questions. What are the benefits? How often, how hot and for how long? What are the risks? For now, he told NPR, he can't give people recommendations.

Ant Shepherd, a physiologist at the University of Portsmouth, put it in terms of what it would take to change public guidance: governments will want large randomized trials, not more small ones.

What it means for you

None of this says sauna is useless, and none of it says it works. The large Finnish associations are a reason to study it, not proof of benefit. If you enjoy the sauna, the honest summary is that the research is promising and unfinished. If you have a heart condition or another health concern, a clinician is the right person to ask about heat.

Where Soma fits

The point that stood out to us is the one about measurement. A result is hard to trust when every lab measures heat, temperature and outcomes in its own way. We think the same is true for a single person. A reading only means something next to earlier readings taken the same way.

That's why Soma Axon is being designed as one closed pod with the same light, cameras and stance every week. Soma is a general wellness product, it doesn't diagnose and it won't tell you whether the sauna is good for you. What we want it to offer is a consistent weekly record, so a change in the number is more likely to be a change in you. The same instrument, every week explains the idea.

Sources, as of October 11, 2026: NPR, Sweating the details: Sauna's potential health benefits draw scientists' interest (October 11, 2026); Laukkanen and colleagues, Association between sauna bathing and fatal cardiovascular and all-cause mortality events, JAMA Internal Medicine (2015); Lee and colleagues, Effects of regular sauna bathing in conjunction with exercise on cardiovascular function: a multi-arm, randomized controlled trial, American Journal of Physiology (2022). This post describes research and isn't medical advice.