Scientists Seek Rigorous Evidence for Sauna and Heat Therapy at Norway Meeting

The organizers said the effort is meant to move heat therapy beyond a niche or fringe area and toward a recognized field of research. Ashley Mason, a clinical psychologist at the University of California, San Francisco, and an associate professor of psychiatry and behavioral science, said, "We want to introduce this as an actual field of research, not something fringy, or woo-woo." Mason is running trials on heat therapy for depression, sleep and other aspects of mental health.

Public interest in sauna and other heat practices has grown through social sauna meetups and the broader wellness and optimization movement. Dr. Hans Hägglund, a hematologist and stem-cell researcher at Karolinska University Hospital in Stockholm, said, "It's really booming." But Hägglund, who has been called the "sauna doctor" in his home country after writing a popular book on the subject, added, "Unfortunately, there is still not very much evidence out there."

The scientific understanding of heat's acute effects on the body is well established. Faced with extreme temperatures, blood vessels dilate, heart rate speeds up and blood is pushed to the skin where it is cooled as people sweat. The body releases hormones and activates heat shock proteins that protect cells. That knowledge has shaped medical care for heat-related illness, but modern medical science has paid considerably less attention to the possible therapeutic benefits of heat exposure.

Interest in those benefits dates back centuries. In the late 1700s, British scientists ran bold experiments on thermoregulation, subjecting themselves and a dog to a piping hot room and observing that their own bodies did not cook, unlike the steak and eggs accompanying them.

Much of the existing sauna research remains difficult to compare. Studies are small, methods vary significantly, and key measurements are sometimes missing, according to NPR News. Mason said, "We're all over the place. If we want to be taken seriously, we need to have consistent terms, so that people understand how to refer to and talk about our work."

Earric Lee, a postdoctoral researcher at the Montreal Heart Institute who is spearheading the initiative, said scientists first need to agree on standards. That process involves dozens of other experts and is intended to set the stage for larger, multisite trials. The questions include what the actual benefits are, how often people need to go, what the risks are and how hot it needs to be. "People want information. I know 'listen to your body' doesn't cut it," Lee said, "but I really can't give you recommendations, and that's the honest truth of it."

Early evidence suggests sauna exposure may hold promise. Passive heat therapy, as it is known in the scientific literature, works the cardiovascular system in ways similar to light physical activity and delivers some of the same benefit, according to NPR News.