Sauna: The Honest Version

Nobody used to talk about saunas...unless they were bathhouses in the 80' and that was a whole different thing. Now half my clients ask me if they should be doing "their protocol" five times a week, like they're following a NASA training schedule. Welcome to wellness in 2026, where a Finnish cultural practice has been repackaged into a $7,000 cedar pod with a chromotherapy panel, a built in red light tower, and a podcast personality assuring you it will fix your inflammation, your insulin resistance, and possibly your divorce.

So is any of this real? Some of it. A surprising amount of it isn't. Let's separate what the evidence actually says from what the wellness industry is selling you.

NOTE: Below are some recent mainstream articles cheerleading the sauna as a near miracle longevity intervention. Read them, then come back. They are largely repeating the same study, often without mentioning that it is a single study.

• Harvard Health: Sauna use linked to longer life, fewer fatal heart problems

• Time Magazine: The Strange Connection Between Saunas and Longevity

• CNN: Red light therapy and saunas may not just be snake oil

• Science Daily: Scientists uncover why sauna bathing is good for your health

What the Evidence Actually Shows

Almost every confident sauna claim you have ever heard traces back to one research group. Dr. Jari Laukkanen, a cardiologist at the University of Eastern Finland, and his team have been mining a long running prospective cohort called the Kuopio Ischemic Heart Disease Study (KIHD), which followed about 2,300 middle aged Finnish men for 20 plus years. Their famous 2015 paper in JAMA Internal Medicine produced the numbers you have been hearing nonstop ever since.

These are the headline figures. Sauna 4 to 7 times per week and you get a 63% reduction in sudden cardiac death, 50% in cardiovascular mortality, and 40% in all cause mortality, compared to people who only sauna once a week. Pause and read that again. A 40% reduction in all cause mortality. From sitting in a hot room. Hmmmm.

For context: Statin therapy in primary prevention populations, an intervention validated by multiple large randomized controlled trials with a well understood biological mechanism and billions of dollars of clinical research behind it, produces about a 9% relative reduction in all cause mortality. A 2022 JAMA Internal Medicine meta-analysis of 21 RCTs (Byrne et al.) found an absolute risk reduction of 0.8% and a relative risk reduction of 9% for statins in primary prevention. The KIHD sauna data is claiming an effect size roughly four times larger than statins, in a passive freely available intervention, on the basis of one observational cohort. That should set off alarms. It does not appear to set off alarms in most of the wellness influencer crowd. It should.

The proposed mechanisms are at least plausible. A 20 minute sauna session raises heart rate into a zone comparable to moderate exercise, transiently lowers blood pressure, improves arterial compliance (measured by pulse wave velocity), and triggers heat shock protein expression. None of this is woo. It's reasonable cardiovascular physiology. The problem is the gap between "produces these acute physiological responses" and "reduces all cause mortality by 40%." That gap is where the wellness industry lives.

If you stop reading here, the case looks airtight. Stop reading here and you'll buy the $7000 cedar pod.

It's Not Just the Finnish Data

In fairness, the KIHD study isn't the only sauna research that exists. The evidence base looks thinner than it actually is because everyone keeps citing the same three Laukkanen papers in a loop. There are other landmark trials, from different countries, on different populations, with different study designs. Three worth knowing:

1. WAON CHF Trial (Tei et al., Japan, 2016). A multicenter randomized controlled trial of "Waon therapy," a specific protocol using a far infrared sauna at 60°C for 15 minutes followed by 30 minutes of warm blanket rest, in patients with chronic heart failure. Published in Circulation Journal. The treatment group showed meaningful improvements in cardiac function, exercise tolerance, and quality of life. Tei Chuwa, the Japanese cardiologist who developed the protocol, has been running this line of research since the 1990s and basically owns this corner of the literature. This is the strongest non Finnish sauna evidence we have, and importantly, it is actually randomized.

2. Scoon et al. (New Zealand, 2007). Six competitive male distance runners did three weeks of post training sauna sessions, about 30 minutes at 90°C, three to four times per week. Result: a 32% increase in time to exhaustion, equivalent to roughly a 2% improvement in 5K performance. The mechanism appears to be plasma volume expansion through heat acclimation. The sample size is six humans, which is roughly the population of a small beer garden, but the finding has been replicated by Stanley et al. in Australia (2015) and several others since. If you train for endurance, this is the most directly useful sauna data in the literature.

3. Oosterveld et al. (Netherlands, 2009). A small pilot study using infrared sauna twice weekly for four weeks in patients with rheumatoid arthritis and ankylosing spondylitis. Statistically significant short term improvements in pain and stiffness during sessions, no flare ups, well tolerated. Worth knowing if you have inflammatory joint issues.

None of these are bulletproof. WAON CHF is on a specific cardiac patient population using a protocol that isn't quite what the rest of the world calls a sauna. Scoon's N is six person sample size. Oosterveld is a pilot. But together they tell a more complete story than "one Finnish cohort," and they do reasonable work supporting the idea that saunas produce real physiological effects in real people across multiple contexts. The point is just that the big mortality and longevity numbers still come from one cohort, and that is where the strongest claims actually rest.

The Skeptic's Corner

This is where it gets interesting, because the loudest people in the sauna conversation tend to skip this part entirely.

The effect sizes are biologically implausible. This is the most important critique and almost nobody makes it. A 40% all cause mortality reduction is the kind of effect size you expect from a transformative cancer therapy, not from passive heat exposure. Statins, with strong RCT validation, deliver about 9%. Smoking cessation in long term smokers, an intervention with massive epidemiological support, delivers somewhere in the 15 to 30% range depending on age and abstinence duration. Sauna is claiming to outperform both. When an observational study reports effect sizes that dwarf the gold standard RCT evidence for established interventions, the most parsimonious explanation is residual confounding, not "we have discovered an unbelievably powerful intervention that the entire field of cardiology has somehow missed for decades."

Almost everything traces back to one cohort. The KIHD study is real, careful work, but it is one population: middle aged Finnish men from the 1980s, in a country where saunas are so culturally embedded that only about 2% of participants never used one. Look at the chart below. The "reference group" is people who sauna once a week. That is not a control group. That is a comparison between Finns who like saunas a lot and Finns who like saunas slightly less. There are essentially no actual non users in the data. As one statistician put it in a Science Media Centre reaction to the paper, it's hard to know what these findings mean in countries where the lifestyle is anything like the rest of the developed world.

NOTE: Almost every dramatic sauna mortality and longevity number you have ever heard comes from one Finnish dataset: the Kuopio Ischemic Heart Disease (KIHD) study, about 2,300 middle aged men from eastern Finland recruited between 1984 and 1989. The Laukkanen research group has published more than ten papers from this single cohort over the past decade, each reported as if it were an independent finding:

• "Sauna reduces cardiovascular mortality" (Laukkanen et al., 2015, JAMA Internal Medicine)

• "Sauna reduces dementia and Alzheimer's risk" (Laukkanen et al., 2017, Age and Ageing)

• "Sauna reduces incident hypertension" (Zaccardi et al., 2017, American Journal of Hypertension)

• "Sauna reduces inflammation related mortality" (Kunutsor et al., 2022, European Journal of Epidemiology)

• "Sauna improves arterial compliance" (Lee et al., 2018, European Journal of Preventive Cardiology)

• "Sauna with low cardiorespiratory fitness still reduces mortality" (Laukkanen et al., 2018, Annals of Medicine)

• "Sauna interacts with systolic blood pressure to reduce mortality" (Laukkanen et al., 2024, Scandinavian Cardiovascular Journal)

  
  

These are not independent findings. They are the same Finnish men sliced different ways. The authors of the 2024 KIHD paper acknowledge this directly in their own limitations section: "potential for type 1 errors due to multiplicity, given the testing of multiple variables for associations with exposures and mortality outcomes within the KIHD study." The one notable independent replication in this entire literature is Knekt et al. (2020) in Preventive Medicine Reports, which confirmed a dementia protective signal in a separate Finnish cohort of about 14,000 people. The cardiovascular mortality and longevity numbers have no such replication. They rest on KIHD alone.

The same cohort has been mined for over a dozen papers. Laukkanen and collaborators have published findings from KIHD on cardiovascular mortality, sudden cardiac death, dementia, Alzheimer's disease, hypertension, stroke, pneumonia, COPD, and more. That is a lot of endpoints from one dataset. Each paper gets reported as an independent finding, but they are not statistically independent. They are all running tests on the same underlying group of Finnish men. When you test enough endpoints across enough subgroups, some come back significant by chance. The repeated mining of a single cohort to produce a steady stream of "sauna prevents X" headlines is one of the most underappreciated problems in this literature, and it is the engine of the wellness industry's sauna content cycle.

The longevity data is all observational. There are no long term randomized controlled trials linking sauna to all cause mortality, and there never will be. The Waon RCT discussed above is randomized, but it's on a specific heart failure population over a much shorter timeframe, not general longevity. You can't blind people to sitting in a 175°F room, and nobody is going to fund a 20 year RCT on a cheap intervention. There is no Mendelian randomization workaround either, because sauna use is not genetically determined. The Mayo Clinic Proceedings review (Laukkanen, Kunutsor, et al., 2018) is admirably honest about this: the entire field is built on cohort data with the usual baggage. Residual confounding. Reverse causation. Regression dilution bias. Inability to prove causation. The whole disclaimer parade.

The free time confounder is doing a lot of work. This is the one nobody wants to talk about. Think about who actually saunas 4 to 7 times per week for 20 plus minutes. That's roughly 2 to 3 hours of pure sauna time, plus changing, showering, and travel if it isn't in your basement. The people doing this are by definition the people who can. These folks are have many privileges the average person does not possess.

Researchers do adjust for income, exercise, BMI, smoking, alcohol. They do not, and cannot, adjust for "has the kind of life where sitting quietly in a hot room five times a week is even an option." The person who can sauna five times a week is also the person who sleeps eight hours, cooks real food, sees friends, trains consistently, and isn't pulling 60 hour weeks while parenting two kids and managing an aging parent. Strip the sauna out of that life and you probably still get most of the outcomes.

The dose response cuts both ways. Defenders point to the dose response curve as evidence of a real causal effect. Fair. But "I have time to sauna seven times a week" also has a dose response with general life stability. The same curve fits both stories. It's not a tiebreaker.

Heat shock proteins are real. The leap to "this is why you live longer" is not. HSP70 goes up after a hot sauna session. That is measured. The translation to mortality benefits in humans is hand waved across the entire literature, including in places where the hand waving has a PhD. Most of the longevity claims for heat shock proteins come from C. elegans (worms) and mouse studies, where you can actually do interventional experiments. Whether the same effects translate to twenty extra years for a middle aged Finnish man who sweats five times a week is a substantial leap that nobody has actually demonstrated.

NOTE: I'm not saying saunas don't do anything. I'm saying the honest version of the claim is "in one Finnish cohort, frequent sauna users had better cardiovascular outcomes through mechanisms that are plausible but unproven, in a study design that can't rule out the possibility that the sauna is partly just a marker for a life that already favors longevity." That's still interesting. It's just not "sauna is the new statin."

The Rhonda Patrick Wellness Influencer Problem

Dr. Rhonda Patrick deserves real credit. She has a legitimate PhD in biomedical science, did real postdoctoral work at the Salk Institute, and she was talking about sauna research years before the wellness influencer crowd discovered it. She also wrote a 2021 review in Experimental Gerontology on sauna use and healthspan, which is more than 99% of people in this space ever do. That said.

She is also a textbook case of how to cherry pick evidence and build a massive platform on a single cohort study. She has cited the KIHD findings on Joe Rogan, Tim Ferriss, Peter Attia, and her own podcast hundreds of times. She rarely emphasizes that it is one observational cohort of Finnish men. She presents the effect sizes (63% reduction in sudden cardiac death, etc.) as if they are settled science, when they are exactly the kind of effect sizes that scream residual confounding to anyone who has spent ten minutes with an epidemiology textbook.

Add the commercial layer. Patrick has partnerships with sauna brands. That doesn't make her wrong, but it does mean the person telling you the evidence is overwhelming is also the person whose business model depends on you believing it.

And to be clear, Patrick is not alone. The credentialed wellness influencer ecosystem is now its own thing. Peter Attia, MD, has built an entire longevity clinic, Early Medical, with reported annual membership fees in the in the high 6 figures, and a podcast empire on largely the same template. His 2023 bestseller Outlive features sauna prominently as part of his "Medicine 3.0" longevity stack. Andrew Huberman, PhD, a Stanford neuroscientist, has done multi hour episodes on deliberate heat exposure that package observational data into confident "protocols" you can follow at home. He routinely cites the Laukkanen numbers without serious skeptical framing. David Sinclair at Harvard does the same maneuver with NAD precursors and resveratrol, where his commercial interest in NMN supplements (he is a co-founder of MetroBiotech) has produced years of running scientific embarrassment, including a public feud with other longevity researchers over the actual human evidence base for his recommendations. The cast rotates but the formula is consistent. None of these are cranks. They are well trained scientists and clinicians with real degrees from real institutions.

The problem is the incentive structure. The podcast and supplement economy rewards certainty, episode length protocols, branded routines, and "the science says" framing. It punishes "the data is mixed and we cannot really tell yet." Nobody downloads three hours of epistemic humility. So even very credentialed people get quietly nudged toward overstating what the evidence actually supports, because that is what the market is paying for. Patrick is the most visible example for sauna specifically. The broader phenomenon is the entire genre, and once you learn to see it, you cannot unsee it.

This is the wellness influencer playbook in three steps:

1. Find a single interesting cohort study.

2. Quote the effect size at every available opportunity, ideally without the limitations.

3. Brand it as "the science" and sell the equipment.

Saunas probably do something. The data is genuinely interesting. The mechanisms are plausible. But "interesting and plausible" is not "settled," and selling certainty where the data warrants caution is exactly how the wellness industry ate the wellness conversation.

NOTE: This is not a Rhonda Patrick takedown. It is a pattern recognition exercise. The same critique applies to most of the longevity podcast circuit. The cherry picking is the feature, not the bug. You don't get a million downloads by presenting nuance and saying "the evidence is interesting but soft, and we can't really tell."

Red Light Saunas and the Infrared Question

Here is where the marketing gets sloppy and you should be precise, because this is where most of the money is being spent.

Infrared sauna uses infrared heaters that warm your body directly, at lower ambient temperatures (110°F to 140°F). The pitch is "sauna benefits without the brutal heat."

Red light therapy is something completely different. Specific wavelengths (usually 660nm and 850nm) delivered by LED panels, with its own much smaller, much more preliminary evidence base for skin and recovery.

A "red light sauna" is typically an infrared sauna with red light panels bolted on. Two different modalities, marketed as one premium thing for about double the price.

Here is the problem.

Almost none of the Laukkanen mortality data applies to infrared saunas. The Finnish studies were done at 80°C in dry traditional saunas. The infrared sauna industry cites that research in their marketing constantly, but the studies were not done on their product. As one sauna review put it, it's a bit like tanning bed companies citing sunshine research.

There is some smaller, shorter term work suggesting infrared can produce similar physiological responses (heart rate, sweat) at lower ambient temperatures, and there's reasonable preliminary evidence for muscle recovery, blood pressure, and inflammation in the short term. Hussain et al. (Complementary Therapies in Medicine, 2022) did a nice randomized crossover trial showing infrared can match some of the acute physiological responses to exercise. That's interesting. It's not 20 year mortality data.

The dramatic claims that infrared sauna companies make (deep cellular detoxification, fat loss, "mitochondrial healing") sail well past what the data supports. If you want what the studies actually studied, you want a hot dry traditional sauna. If you want infrared because it's more tolerable and you'll actually use it, that's a defensible choice. Just don't pretend you're getting the same evidence base. You're buying a different product. The infrared sauna companies know this. That's why the marketing works so hard to obscure it.

NOTE: There is also a category of "near infrared sauna" using halogen incandescent bulbs that emit a broader spectrum, often marketed by alternative health figures. The evidence base here is essentially nonexistent. It is heat plus light plus vibes.

The Bottom Line

If you have access to a sauna and you enjoy it, use it. The downside risk is low assuming no unstable cardiovascular conditions. The acute physiological effects are real. The recovery benefits after training are decent. The relaxation and the ritual alone have value, and "things that get you to sit quietly for 20 minutes" are a vanishingly rare commodity in modern life. As a coach, I have no problem recommending sauna use to most of my clients, most of the time.

What you shouldn't do:

1. Take out a loan for a $7,000 infrared sauna based on Finnish cohort data that does not apply to it.

2. Believe "20 minutes a day adds X years to your life" framing as if it's settled science.

3. Skip training to sit in a hot box. The exercise data is much stronger than the sauna data and they are not substitutes. If you want the gym work that actually moves the needle on cardiovascular health, longevity, and bone density, progressive resistance training is the foundation. The sauna is at best a useful addition.

4. Trust anyone selling you certainty on this question. The honest version of the pitch is "probably good, evidence is interesting but soft, and the people who do it consistently are also doing a lot of other things right."

The sauna might genuinely be helping. It might also just be a comfortable marker for a life you'd want anyway. Both of those are reasonable hypotheses given the current data. Anyone telling you the answer is settled is selling you something. Usually a sauna.

Practical Tips

• Use what you have access to. A traditional gym sauna at 175°F is closer to the studied product than a $5,000 home infrared unit.

• Aim for 15 to 20 minutes per session if you tolerate it. The mortality data is built on session durations in that range. Going longer doesn't appear to add benefit and significantly raises dehydration risk.

• Hydrate before, during, and after. Sweat losses in a hot sauna can be 0.5 to 1 liter per session.

• Don't sauna before training. Pre exercise heat stress reduces performance. Save it for after, or on rest days.

• Be careful combining alcohol and sauna. This combination has been implicated in a meaningful percentage of sauna related deaths in Finland. Yes really.

• Skip it if you have unstable cardiovascular disease, recent heart attack, very low blood pressure, or are pregnant. Talk to your doctor first.

• Don't trust the dramatic claims. Detoxification, fat loss, cellular healing. The data does not support these. The acute relaxation and recovery benefits, plus probably some cardiovascular adaptation, are enough on their own.

References:

• Laukkanen, T., Khan, H., Zaccardi, F., & Laukkanen, J. A. (2015). Association between sauna bathing and fatal cardiovascular and all cause mortality events. JAMA Internal Medicine, 175(4), 542 to 548.

• Laukkanen, T., Kunutsor, S. K., Khan, H., Willeit, P., Zaccardi, F., & Laukkanen, J. A. (2018). Sauna bathing is associated with reduced cardiovascular mortality and improves risk prediction in men and women: a prospective cohort study. BMC Medicine, 16(1), 219.

• Laukkanen, J. A., Laukkanen, T., & Kunutsor, S. K. (2018). Cardiovascular and other health benefits of sauna bathing: a review of the evidence. Mayo Clinic Proceedings, 93(8), 1111 to 1121.

• Kunutsor, S. K., Laukkanen, T., & Laukkanen, J. A. (2023). Does the combination of Finnish sauna bathing and other lifestyle factors confer additional health benefits? A review of the evidence. Mayo Clinic Proceedings, 98(6), 915 to 926.

• Hussain, J. N., Cohen, M. M., Mantri, N., O'Malley, C. J., & Greaves, R. F. (2022). Infrared sauna as exercise mimetic? Physiological responses to infrared sauna versus exercise in healthy women: a randomized controlled crossover trial. Complementary Therapies in Medicine, 64, 102798.

• Patrick, R. P., & Johnson, T. L. (2021). Sauna use as a lifestyle practice to extend healthspan. Experimental Gerontology, 154, 111509.

• Tei, C., Imamura, T., Kinugawa, K., et al. (2016). Waon therapy for managing chronic heart failure: results from the multicenter prospective randomized WAON CHF study. Circulation Journal, 80(4), 827 to 834.

• Scoon, G. S. M., Hopkins, W. G., Mayhew, S., & Cotter, J. D. (2007). Effect of post exercise sauna bathing on the endurance performance of competitive male runners. Journal of Science and Medicine in Sport, 10(4), 259 to 262.

• Oosterveld, F. G. J., Rasker, J. J., Floors, M., et al. (2009). Infrared sauna in patients with rheumatoid arthritis and ankylosing spondylitis: a pilot study showing good tolerance, short term improvement of pain and stiffness, and a trend towards long term beneficial effects. Clinical Rheumatology, 28(1), 29 to 34.

• Byrne, P., Demasi, M., Jones, M., Smith, S. M., O'Brien, K. K., & DuBroff, R. (2022). Evaluating the association between low density lipoprotein cholesterol reduction and relative and absolute effects of statin treatment: a systematic review and meta-analysis. JAMA Internal Medicine, 182(5), 474 to 481.

• Science Media Centre (2018). Expert reaction to study looking at sauna use and cardiovascular death risk. sciencemediacentre.org.

Want more evidence based fitness content without the nonsense? Visit the Joachim's Training blog for more on separating science from supplement marketing and bro science from actual biology.

Tags: sauna, recovery, longevity, heart health, wellness industry, fitness