The famous sauna longevity study used Finnish saunas, not infrared cabins

Key takeaways

• A 2015 Finnish study linked sauna use four to seven times a week with a 40% lower risk of death in men than once-weekly use, but it studied traditional saunas, and its authors said the results can’t be applied directly to other types.
• Infrared saunas warm your skin with radiant energy rather than mainly with hot air; Japan’s medical Waon therapy, tested in hospital trials, holds its cabin at 60°C (140°F).
• A 2016 randomized trial of infrared Waon therapy in 149 heart failure patients at 19 Japanese hospitals found better walking distance after two weeks but missed its main goal.
• Sweat is mostly water, and your liver and kidneys do the real clearing; the FDA and FTC have warned sauna sellers over toxin, disease and COVID-19 claims.
• Skip alcohol, keep sessions short, replace the fluid you sweat, stand up slowly, and ask a clinician first if you have heart disease, faint easily or are pregnant.

In 1984, researchers in eastern Finland began asking middle-aged men a simple question: how often do you take a sauna? Then they followed the men for about 20 years and tracked who died, and from what¹.

The answer made headlines in 2015. Among 2,315 men, those who used a sauna four to seven times a week had a 40% lower risk of dying from any cause than men who went once a week¹². Their risk of sudden cardiac death was 63% lower².

That work, from the Kuopio Ischemic Heart Disease Risk Factor Study, supplies most of the evidence behind claims that saunas help you live longer⁵. But it measured one specific thing: the traditional Finnish sauna, with dry air typically heated to 80–100°C (176–212°F) at face level¹.

The authors wrote that their results “cannot be directly applied” to other kinds of saunas¹. That includes the infrared cabins now sold for homes, gyms and spas.

So what do we know about infrared saunas themselves? Less than the ads suggest, more than nothing, and enough to use one wisely.

The Finnish study showed a strong link, not proof

The Kuopio study is a cohort study. Researchers watch a group of people over time and look for patterns. That design can show that two things travel together, but it can’t show that one causes the other.

The men described their sauna habits once, on a questionnaire, sometime between 1984 and 1989¹⁵. Nobody checked whether those habits held for the next two decades.

Almost everyone used a sauna. Only 12 men had no regular sauna habit, so the study compared once a week with more often, not sauna with no sauna³. The groups also weren’t alike. Frequent users differed from weekly users in age, drinking, smoking and exercise⁵.

The researchers did adjust for many factors, including fitness, blood pressure, alcohol and socioeconomic status¹. Even so, Rita Redberg, in an editor’s note published alongside the study, wrote that no one knows why the frequent users lived longer⁴. She listed the heat itself, relaxation, a life with more leisure, and friendship in the sauna as possibilities⁴.

Everyone in the study was a man aged 42 to 60¹. And the team has published many papers from this one group of men, twelve in 2018 alone, according to McGill University’s Office for Science and Society⁵. More papers from the same men don’t add up to new, independent evidence.

None of this means the finding is wrong. It means the finding is a strong lead for traditional saunas. It says nothing direct about infrared ones.

Infrared heats you more than the air around you

A Finnish sauna is a hot room filled with dry air, with humidity around 10%–20%¹. In the Kuopio study, the men reported an average sauna temperature of about 79°C (174°F)¹.

That heat works the body hard. Heart rate can climb to about 100 beats a minute in a moderate session and near 150 in a hot one, similar to light or moderate exercise¹. Blood flow to the skin jumps from about 5%–10% of the heart’s output to 50%–70%⁵. Most bathers lose about half a kilogram of sweat per session, a little over a pound¹⁵.

An infrared sauna works differently. Its panels give off infrared energy that warms your skin directly, instead of relying mainly on hot air. The FDA’s category for these devices describes products that emit infrared energy, at wavelengths of roughly 700 to 50,000 nanometers, to provide topical heating⁷.

Because the heat reaches you as radiation, the air can stay cooler. Japan’s Waon therapy, the infrared routine tested in hospital trials, uses a cabin held at 60°C (140°F)⁶. That is well below the 80–100°C range recommended for a Finnish sauna¹.

Cooler air does not mean no strain. In the Waon routine, 15 minutes in the cabin raises core body temperature by about 1.0–1.2°C⁶. That is enough to make your heart and blood vessels work to shed heat.

Infrared’s key evidence comes from Japanese heart clinics

“Waon” means soothing or comfortable warmth in Japanese⁶. By 2016, the trial’s authors wrote, it had been used in Japan to treat advanced heart failure for more than 20 years⁶.

The routine is precise. A patient sits in a far-infrared dry sauna at 60°C for 15 minutes, then lies under a warm blanket for 30 more⁶. Staff weigh the patient before and after and give cold water to replace the sweat⁶.

The key test is the WAON-CHF trial, published in 2016 in Circulation Journal⁶. It was a randomized controlled trial, meaning patients were assigned by chance to Waon or to usual care. Researchers at 19 Japanese centers enrolled people admitted to the hospital with heart failure, and 149 patients were analyzed⁶.

The Waon group had 10 sessions over two weeks⁶. Here is what the researchers found:

• The main goal was missed. BNP, a blood marker of heart strain, fell in the Waon group, but the gap between groups wasn’t statistically significant⁶.
• Walking improved. Six-minute walking distance rose by about 45 meters with Waon, compared with about 13 meters in the usual-care group⁶.
• Some heart measures improved. Heart size on chest X-ray shrank slightly, and patients’ heart failure class, a doctor’s rating of symptoms, got better⁶.
• Pumping strength didn’t change. The heart’s ejection fraction, the share of blood pumped out with each beat, was no different between groups⁶.

Nobody died, and there were no serious side effects⁶. Minor problems included low blood pressure in two patients and low blood volume in two others⁶. One Waon patient with a history of atrial fibrillation, an irregular heart rhythm, had a short bout of it⁶.

The authors listed clear limits. The treatment couldn’t be hidden from patients, so the trial wasn’t blinded; it lasted only two weeks; and it didn’t track survival⁶. They also note that the 2010 Japanese Circulation Society heart failure guideline gave Waon its top recommendation level, Class I⁶.

The lesson: this is a supervised medical treatment with weigh-ins and fluid replacement. It is not evidence that a home session helps, or is safe for, someone with heart failure.

The trial’s reference list also points to small early studies of heat therapy in Japan for peripheral artery disease, the lung disease COPD, chronic fatigue syndrome and fibromyalgia, some led by the same team⁶. These are early signals, not settled answers.

An evidence map for infrared sauna claims

This table uses four levels: strong evidence, promising but early, not enough evidence, and evidence says no (or unsafe).

Claim	Evidence level	What the research shows
Regular Finnish-style sauna use helps you live longer	Promising but early	Large Finnish study of men found strong links, but it was observational, used one questionnaire and had almost no non-users135
Supervised infrared (Waon) therapy helps heart failure	Promising but early	One randomized trial of 149 hospital patients: better walking and symptom class, main blood-marker goal missed, two weeks only6
Infrared heat helps artery disease, fatigue or fibromyalgia	Promising but early	Small early studies from Japan, cited by the WAON-CHF team6
Infrared heat briefly eases minor muscle and joint aches	Promising but early	Some infrared saunas are FDA-cleared as heat lamps for this narrow use; a clearance is not a large sauna trial7
Sweating in a sauna detoxes heavy metals or chemicals	Evidence says no	Sweat is mostly water; the liver and kidneys clear most compounds; sweat holds too little fat to remove long-lasting pollutants510
Infrared saunas treat or prevent cancer, kidney disease or COVID-19	Not enough evidence	FDA and FTC warned sellers who made these claims; the FTC said no scientific evidence showed such products could prevent or treat COVID-19789

Sweat is mostly water, and your liver and kidneys do the detox

“Detox” is the claim you’ll meet most often in sauna ads. The idea is that heat flushes heavy metals and chemicals out through your pores. Some infrared sellers add that their heat reaches deeper, so it pulls out more.

The chemistry doesn’t back this up. Sweat is almost all water. It also carries a bit of mineral content and tiny traces of other compounds¹⁰. Your liver and kidneys handle most of the substances your body needs to get rid of¹⁰.

Joe Schwarcz of McGill University’s Office for Science and Society writes that there is “zero evidence” that infrared heat releases more toxins¹⁰.

Persistent organic pollutants, long-lasting chemicals that build up in body fat, are a favorite target of detox ads. Canadian researchers calculated that sweat carries far too little fat to clear them in meaningful amounts⁵.

Regulators have pushed back. In 2022, the FDA sent a warning letter to a Kansas company whose website said its far-infrared sauna helped the body get rid of toxins and helped prevent kidney failure, among other disease claims⁷.

During the pandemic, the FTC warned two infrared sauna sellers, Enlighten Sauna and Celebration Saunas, to stop claiming their saunas could fight COVID-19⁸⁹. Enlighten’s website had linked infrared sessions to a stronger immune system against the coronavirus, and the FTC gave it 48 hours to respond⁸. The agency said there was no scientific evidence for such claims⁹.

Sweating does have real effects. It cools you. But extreme sweating can dehydrate you and make your kidneys’ job harder¹⁰. The thing detox ads celebrate is the thing you need to manage.

What “FDA-cleared” means on a sauna

Some infrared saunas carry an FDA clearance. The one named in that 2022 warning letter shows how narrow a clearance can be. It was cleared as an infrared heating lamp under the federal rule 21 CFR 890.5500⁷.

Its cleared uses were short-term relief of minor muscle and joint pain and stiffness, arthritis joint pain, a temporary rise in circulation where the heat is applied, and muscle relaxation⁷. The clearance also covered saying it may help with muscle spasms, minor sprains and strains, and minor back pain⁷.

That was the whole list. The seller’s website went further, with claims about cancer, kidney function, heart disease, chronic illness and skin conditions such as eczema and psoriasis⁷. FDA said those claims were major changes to the device’s intended use, which made it adulterated and misbranded under federal law⁷.

So when a sauna is “FDA-cleared,” ask a follow-up question: cleared for what? For the difference between registered, cleared and approved, see our buyer’s map to wellness devices.

A safer infrared session, step by step

This routine borrows from the hospital Waon protocol and from what Finnish research shows about heat and blood pressure. It’s a starting point for healthy adults, not a medical prescription.

1. Check yourself first. Skip the session if you feel sick, feverish, dizzy or already dehydrated.
2. Stay sober. In Finland, 230 people died of overheating from 1970 to 1986, mostly in saunas and often after drinking⁵. Alcohol was also a major factor in the rare sudden deaths that follow sauna use¹.
3. Weigh in and drink. Waon patients are weighed before and after and given water to replace their sweat⁶. Any drop on the scale is water, not fat. Drink to replace it.
4. Keep it short, and set a timer. The medical Waon routine uses 15 minutes at 60°C⁶. If you’re new, start with less, and don’t assume longer is better.
5. Stand up slowly. Blood pressure often drops right after a session, so people prone to dizziness on standing should take care¹. Sit for a minute before you walk out.
6. Rest afterward. Waon patients lie quietly for 30 minutes after the cabin⁶. Give yourself a calm cool-down before you drive or exercise.
7. Leave at the first warning sign. Get out if you feel faint, confused, sick to your stomach, or have a pounding headache or chest discomfort.

Talk with a clinician before you start if any of these apply:

• You have heart failure, a heart rhythm problem or other heart disease. Infrared heat for heart failure was tested only in hospitals, with monitoring⁶.
• You faint easily or take medicine that lowers blood pressure, since heat can drop it further¹⁶.
• You are pregnant, have kidney disease, have an implanted medical device, or are thinking about a session for a child. The research in this article involves only adults, mostly men and hospital patients¹⁶.

When to get help. If someone faints, becomes confused, or has chest pain or trouble breathing in or after a sauna, get them out, cool them down and call 911. Report a sauna that burns, shocks or injures you to the FDA’s MedWatch program, and report misleading health claims to the FTC at ReportFraud.ftc.gov.

Warmth is an old comfort. Let the evidence keep it a good one

Natural health has always valued rest, warmth and time with people you care about. Read carefully, the sauna research points the same way.

Redberg’s list of reasons Finnish sauna users might live longer reads like a description of a good life: heat, relaxation, leisure and friends⁴. Japanese doctors named their treatment for soothing warmth, not for purging toxins⁶.

Those are better reasons to sit in a sauna than detox. Your body already has a cleanup system in your liver and kidneys, working every day¹⁰. A sauna can be a pleasant way to unwind and care for yourself. Be wary of anyone who sells it as a cure.

Questions readers ask

The bottom line

Infrared saunas offer real, gentle heat and a modest research record: one mid-sized trial in heart failure patients in the hospital, a few small early studies, and a narrow FDA clearance for minor aches. The famous longevity findings belong to Finnish saunas, and even those show a link, not proof.

If you enjoy the warmth, use it for relaxation. Keep sessions short and sober, replace what you sweat, and leave detox promises at the door. If you have a heart or blood pressure condition, take daily medicines or are pregnant, talk with a clinician before you start.

Related reading

• “FDA registered” isn’t “FDA approved”: a buyer’s map to wellness devices
• Most health products aren’t scams, but many just haven’t been proven
• How miracle-cure scams borrow the language you trust
• A cold plunge eases soreness but can shrink your muscle gains
• Six questions to ask before you buy anything for your health

Sources

1. Laukkanen T, Khan H, Zaccardi F, Laukkanen JA. “Association Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality Events.” JAMA Internal Medicine, 2015. pubmed.ncbi.nlm.nih.gov
2. American College of Cardiology. “Is Sauna Use Associated With Reduced Risk of CV Events?” ACC, 2015.
3. NEJM Journal Watch CardioExchange. “Study Links Sauna Use to Better Health.” Massachusetts Medical Society, 2015. blogs.nejm.org
4. Redberg RF. “Editor’s Note: Health Benefits of Sauna Bathing.” JAMA Internal Medicine, 2015. jamanetwork.com
5. Jarry J. “Sweating Out the Hype Over the Finnish Sauna.” McGill University Office for Science and Society, 2021. mcgill.ca
6. Tei C, Imamura T, Kinugawa K, et al. “Waon Therapy for Managing Chronic Heart Failure: Results From a Multicenter Prospective Randomized WAON-CHF Study.” Circulation Journal, 2016. jstage.jst.go.jp
7. U.S. Food and Drug Administration. “Warning Letter: Living Foods LLC, CMS #622648.” FDA, 2022. fda.gov
8. Federal Trade Commission. “Warning Letter to Enlighten Sauna.” FTC, 2020. ftc.gov
9. Federal Trade Commission. “The FTC Directed 30 More Marketers to Stop Making Unsupported Claims That Their Products and Therapies Can Effectively Prevent or Treat COVID-19.” FTC, 2021. ftc.gov
10. Schwarcz J. “Sweating Like a Pig.” McGill University Office for Science and Society, 2018. mcgill.ca