A cardiologist in Finland spent 20 years measuring what weekly sauna use does to the heart. The findings have reshaped how longevity researchers and wellness hotels think about heat.
There are approximately 3.3 million saunas in Finland — one for every 1.7 residents, which works out to a sauna in nearly every home, most workplaces, and all lakeside cottages, according to UNESCO. The word itself is one of the very few Finnish words to have entered English unchanged. Finns conduct business in saunas, negotiate contracts, and welcome guests; historically, saunas were used for childbirth, the logic being that the sauna — kept meticulously clean, reliably hot — was the most hygienic space in the household. None of this is new. What is new is what happened when Dr. Jari Laukkanen, a cardiologist at the University of Eastern Finland, decided in the early 2000s to actually measure what decades of habitual sauna use were doing to the cardiovascular systems of middle-aged Finnish men.
The answer, published in JAMA Internal Medicine in 2015, was striking enough that it has reshaped how cardiologists, longevity researchers, and eventually wellness hotels think about heat. Men who used the sauna four to seven times a week had a 63 percent lower risk of sudden cardiac death and a 50 percent lower risk of fatal cardiovascular disease than those who went once a week. The effect was dose-dependent: the more frequent the use, the larger the protection. Laukkanen’s team subsequently found that regular sauna use was also associated with reduced risk of stroke and lower incidence of both dementia and Alzheimer’s disease.
What the heat is actually doing
The sauna mechanism runs through several pathways simultaneously. Core body temperature during a Finnish sauna session — between 80°C and 100°C (176°F to 212°F), with humidity introduced by pouring water over hot stones — rises by one to two degrees, triggering the same systemic responses as moderate aerobic exercise: heart rate increases, cardiac output rises, blood vessels dilate. Heat shock proteins, produced in response to the thermal stress, repair damaged cellular proteins and are associated with reduced inflammation markers. A 2024 study in the Journal of Applied Physiology specifically examined Finnish sauna bathing in patients with coronary artery disease and found significant improvements in vascular function and blood pressure following a controlled protocol of regular sessions. The parasympathetic nervous system — which governs rest and recovery — becomes dominant in the cooling phase after a session, the period most practitioners consider as important as the heat itself.
Rhonda Patrick, a biochemist who has spent several years translating this research for general audiences through her FoundMyFitness platform, has published a thorough lay syntheses of the sauna literature, covering the cardiovascular, cognitive, and hormonal effects across the full body of published research. One standout data point: growth hormone output can increase by up to 200 percent following a single sauna session, depending on duration and temperature — a finding that has made the practice particularly interesting to athletic recovery specialists. The cardiovascular findings are what the cardiologists have noticed. In a 2024 paper in Scandinavian Cardiovascular Journal, Laukkanen noted that blood pressure reduction from regular sauna use was comparable in magnitude to what is typically achieved through pharmaceutical intervention in mild hypertension cases.
From Nordic bathhouse to American market
Lady Gaga, who manages fibromyalgia, has said that infrared sauna is among the most effective tools in her daily protocol: “I still deal with bone inflammation from my injury two years ago. But I keep control of pain with an infrared sauna. A great investment for everyone; I use mine every day,” she said in an Instagram post. LeBron James has made it a post-game recovery staple. Gwyneth Paltrow keeps one at home. The commercial market has followed: the U.S. infrared sauna market was valued at approximately $290 million in 2025 and is projected to reach nearly $400 million by 2030, driven largely by home installations and spa adoption in cities where bathhouse culture has taken hold — New York, Los Angeles, Austin, and Portland among the most established.
How well does an infrared sauna compare to a Finnish sauna for anyone trying to apply Laukkanen’s research to their own practice? Traditional saunas heat the air around the body; infrared saunas use light waves to heat body tissue directly, at lower ambient temperatures — typically 50 to 60°C. The Laukkanen studies, and the broader Finnish literature, were conducted entirely on traditional Finnish sauna. Whether infrared produces equivalent cardiovascular outcomes remains an open question in the peer-reviewed literature, with some studies suggesting comparable parasympathetic activation and others finding the lower thermal dose insufficient to reproduce the full protective effect. “The key variable is the thermal load,” Laukkanen noted in his 2024 follow-up paper. “Duration and temperature together determine dose.”
For the documented version — the one the cardiologists are actually writing about — the experience is most faithfully reproduced at traditional Finnish-style spas, Nordic wellness hotels, and the growing number of bathhouse-style facilities in American cities that have imported the full Finnish protocol, including the alternating heat-and-cold contrast that the research treats as essential. The Laukkanen data was built on a habit of four to seven sessions a week. What it does not support is the idea that occasional sauna use produces the same outcomes. What it does suggest is that Finland built its entire civic wellness infrastructure around something that was, all along, working.
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