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Modern life offers us a lot of control over temperature. We push the thermostat up or down, put on layers, take them off. We avoid extreme temperatures when we can help it. But some scientists believe that putting people in a hot spot in a controlled way could be good for them. NPR's Will Stone recently traveled to Norway to speak with researchers who are interested in sauna and other forms of heat.
WILL STONE, BYLINE: The study of how heat affects our body isn't new. In the late 1700s, a British doctor ran a bold set of experiments. He brought steak and eggs into a piping-hot room and observed that, unlike the food, his own body did not cook. Our acute response to heat and how our body keeps cool is now well understood. Faced with extreme temperatures, blood vessels dilate, heart rate speeds up, and blood is pushed to the skin where it cools down as we sweat. Our body releases hormones and activates heat shock proteins that protect our cells. This knowledge has shaped medical care, for example, with heat-related illness. But how to use heat to improve health...
HANS HAGGLUND: Unfortunately, that question is easy to answer. There is not very much evidence out there.
STONE: Dr. Hans Hagglund is a hematologist at the Karolinska University Hospital in Stockholm, though he was here in Norway, where I interviewed him in a sauna for a symposium on heat therapy.
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STONE: He even wrote a popular book on the topic, earning him a title from the Swedish Sauna Academy.
HAGGLUND: After that, I was named the Sauna Doctor.
STONE: Hagglund is thrilled the practice is attracting more followers. It's become a social outlet and a staple of the broader wellness movement.
HAGGLUND: It's really booming, and it's here to stay, I think.
STONE: Meanwhile, most of the claims floating around online are not based on the kind of well-controlled human studies that medicine relies on to establish the benefits and risks of a given therapy. This is what Hagglund and others are hoping to change.
EARRIC LEE: Give it prominence. Let people understand that, you know, this is not some woo-woo or, you know, some kind of snake oil.
STONE: Earric Lee is a postdoctoral researcher at the Montreal Heart Institute and lead scientist at a nonprofit called the Sauna Research Foundation. And he spends a lot of time explaining to friends and other scientists what he does.
LEE: When I tell them heat therapy, they're like, heat therapy - what do you mean heat therapy? I'm like, well, you use heat to improve your health. Is that a thing?
STONE: It is, and Lee's pushing for the field to gain more legitimacy. That's why his organization recently convened scientists from around the world at a trendy sauna resort outside Oslo so they could hash out how to rigorously study heat therapy and to form an organizing scientific body to steer the field. Ultimately, the goal is to answer some pretty basic questions. What's it good for? How hot should it be? What are the risks?
LEE: How much do I do and all that kind of stuff. And I have a hard time answering that question, and I know listen to your body doesn't cut it. People want information.
STONE: There are certainly reasons to believe heat, delivered as a strong stimulus in a time-limited manner, holds promise for health. It works our cardiovascular system similar to light exercise and delivers some of the same benefits. Plus, influential research, mostly from Finland, suggests people who spend more time in the sauna live longer and have lower rates of cardiovascular disease and even Alzheimer's. While these findings are encouraging, Lee says they are observational studies, so you can only conclude so much about safety or how effective it is.
LEE: To change policy, we have to do the not-so-sexy stuff. We need to test it out in a trial.
STONE: All of this could lay the foundation for medical societies or governments to one day recommend heat therapy alongside other lifestyle interventions, like exercise. And the research is starting to pick up. For example, Lee has run one of the only randomized controlled trials on sauna bathing, showing that adding it to exercise offered extra benefits for people at risk of cardiovascular disease. Others are focusing on mental health. In her research, Ashley Mason, a clinical psychologist at the University of California, San Francisco, is looking at different forms of heat therapy - infrared machines, Finnish sauna and heated blankets.
ASHLEY MASON: Scientists around the world are getting interested in this and figuring out ways to study heat therapies, but we're all over the place. We need to establish - how do we write about our work? What are the standards? What are the norms? What are the terms? What are the definitions? Do we agree about them?
STONE: These are the growing pains for a new field of scientific study, even one built on age-old practices.
Will Stone, NPR News, Oslo.
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