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Not medical advice. The Atlas is not a substitute for a clinician who can examine you.

Sauna

Sauna Bathing · Finnish & Infrared Heat

Evidence grade 4 of 5, Strong. Read how the Atlas grades evidence.

3 human trials, about 40 studies, >2,300 participants men in the KIHD cohort; about 1,688 men and women in the 2018 extension. The written rationale for this grade is still being prepared.

FDA
Saunas are sold as general wellness products and are not FDA-cleared to treat, prevent, or cure any disease. No medical device clearance underwrites the heart-health or longevity claims marketed by manufacturers.
WADA
Not a prohibited substance or method. Sauna and heat acclimation are used openly in elite sport for recovery and plasma-volume expansion; nothing in the WADA Prohibited List restricts passive heat exposure.

Reference only. Not medical advice.

What can go wrong

Heat causes vasodilation and fluid loss, so dehydration, lightheadedness, and fainting are the common acute risks. Alcohol before or during a sauna sharply raises the danger of hypotension, arrhythmia, and sudden death; Finnish and Korean forensic series link most sauna deaths to intoxication, and a drunken bather should never be left alone in the heat. People with unstable angina, recent heart attack, severe aortic stenosis, or poorly controlled blood pressure should not sauna without medical clearance. Pregnancy warrants particular caution: obstetric guidance advises against raising core temperature above about 39 C, especially in the first trimester when maternal overheating has been associated with neural-tube defects, so anyone who is pregnant should speak with their obstetric provider before using a sauna. The very young and the elderly need shorter, cooler sessions. Sauna is not a substitute for prescribed cardiac care. Anyone with heart disease, on multiple medications, or who feels unwell should consult a qualified clinician before starting.

The headline evidence comes from the Kuopio Ischaemic Heart Disease (KIHD) cohort in eastern Finland, led by Jari and Tanjaniina Laukkanen. In a 2015 JAMA Internal Medicine analysis of 2,315 middle-aged men followed a median 20.7 years, men using a sauna 4 to 7 times weekly versus once weekly had lower sudden cardiac death (HR 0.37), fatal cardiovascular disease (HR 0.50), and all-cause mortality (HR 0.60), with longer sessions tracking further reductions. Later KIHD papers reported lower incident hypertension (Zaccardi 2017; HR about 0.54) and lower dementia and Alzheimer's risk (Laukkanen 2017, Age and Ageing; roughly 65 to 66 percent lower). A 2018 BMC Medicine extension added women (1,688 participants, 51.4 percent women, median 15 years) and found cardiovascular-mortality HR 0.23 for the most frequent users. These findings are consistent and dose-responsive, and they adjust for fitness and known risk factors. They remain observational, so frequent sauna users are likely healthier and more active in ways no model fully captures, and reverse causation (sick people sauna less) is plausible; causation is not established. The controlled evidence is small and limited to surrogate endpoints, and it is mixed. A 2022 randomized trial found exercise plus post-exercise sauna lowered blood pressure and raised fitness more than exercise alone, while a 2023 randomized trial in stable coronary-artery-disease patients found eight weeks of sauna did not improve vascular markers. Infrared evidence is thinner; the strongest is Japanese Waon therapy at 60 C far-infrared, where the randomized WAON-CHF study in heart-failure patients improved ejection fraction and lowered BNP, a clinical population rather than primary prevention.

The strongest human longevity signal for any heat protocol comes from one Finnish town followed for two decades.

What people take it for

What it is taken for. Approval, where it exists, covers only some of these.

  • Cardiovascular conditioning and blood-pressure support in generally healthy adults
  • Post-exercise recovery and heat acclimation for athletes, including plasma-volume expansion
  • Adjunct comfort and functional improvement in chronic heart failure (Waon far-infrared therapy, under medical supervision)
  • Relaxation, sleep support, and stress reduction
  • Cultural, social, and ritual bathing

What people get wrong

  • Often saidSauna sweats out toxins and detoxifies your body.

    ActuallySweat is roughly 99 percent water plus electrolytes; the liver and kidneys handle the cleansing the body needs. Studies detect only trace heavy metals and BPA in sweat, in amounts too small to be biologically meaningful, and Cleveland Clinic notes there is not enough evidence that sweating through exercise or a sauna purifies the body. Measurable benefits track to cardiovascular and heat-adaptation effects, not toxin removal.

  • Often saidInfrared saunas have the same proven heart benefits as traditional saunas.

    ActuallyThe mortality, dementia, and hypertension data come from hot, humid-capable Finnish saunas. Infrared trials are small and mostly short-term; the best infrared evidence is the randomized WAON-CHF study of 188 heart-failure patients using 60 C far-infrared, which improved ejection fraction and lowered BNP in a sick clinical population, not in healthy prevention. The two should not be treated as interchangeable.

  • Often saidThe Finnish studies prove sauna makes you live longer.

    ActuallyThey show a strong, dose-responsive association, not proof. The KIHD findings are observational and drawn largely from one eastern-Finnish population, so healthier-user bias and reverse causation cannot be excluded, a limitation the study authors and independent statisticians both emphasize. No randomized trial has demonstrated a mortality benefit, and the small controlled trials that exist test only surrogate endpoints and report mixed results.

Who profits, and who pushes back

  • Rhonda Patrick

    Promotes itBiochemist and science communicator who popularized the KIHD sauna data

    Unincentivized academic-style communicator; cites the Laukkanen papers directly. Verify her summaries against the primary studies, which she generally represents fairly.

  • Jari Laukkanen

    Promotes itCardiologist and lead KIHD investigator

    Primary researcher behind most of the human evidence; presents findings with appropriate observational caveats in the source papers.

  • Infrared sauna brands (Sunlighten, Clearlight)

    Sells this. Has a commercial interest in a product sold as this compound, as of July 2026.

    Promotes itConsumer infrared sauna manufacturers

    PAID commercial sellers. They frequently borrow the traditional-sauna Finnish mortality data to market infrared units, an evidence transfer the studies do not support.

  • Prof Kausik Ray

    Pushes backProfessor of Public Health, Imperial College London

    This is a 15 year observational study (so it cannot prove causation). People who adopt health behaviours e.g. sauna use may have other favourable characteristics, diet or lifestyle adherence to therapies not captured in the study, so we cannot be certain unmeasured confounders did not account for the findings.

  • Prof Kevin McConway

    Pushes backEmeritus Professor of Applied Statistics, The Open University

    It remains possible that there are other differences between frequent and less frequent sauna users that are the real cause of the difference in death rates, rather than the actual sauna use.

Where the research comes from

Share of published research by country of origin.
PlaceShare of published research
Northern Europe (Finland, Baltics, Scandinavia)46%
East Asia (Japan, Korea)22%
North America16%
Russia and Eastern Europe10%
Rest of world6%

Research published from: Finland (core cohort evidence); Japan (Waon therapy trials).

How we got here

Heat bathing is one of humanity's oldest and most globally distributed health practices, and its lineage is far more non-Western than the modern Finnish sauna branding suggests. In Finland the earliest form was the savusauna, a smoke sauna: an earthen dugout or log room where a large stone pile (kiuas) was heated by burning wood for hours, the smoke vented, and water thrown on the stones for steam (loyly). It served for bathing, childbirth, healing, and even preparing the dead. In parallel and entirely independently, Indigenous peoples across North America built sweat lodges, dome frames covered with hides or earth where water is poured over fire-heated stones, used as sacred purification ceremonies rather than mere hygiene. In Mesoamerica the temazcal (from Nahuatl temazcalli, house of heat) was used by Maya, Aztec, and Toltec cultures for ritual cleansing, healing, and postpartum recovery, and survives in Mexico today. The Russian banya, of Finno-Ugric roots and recorded in Novgorod by the 11th century, paired intense steam with birch-branch whisking (venik). Across the Islamic world the hammam grew from Roman and Byzantine bathing into a central social and spiritual institution from North Africa to Anatolia. Roman thermae industrialized heat bathing with hypocaust underfloor heating and graded hot, warm, and cold rooms. In East Asia, Japanese onsen and sento bathing and Korean kiln saunas, the ancestors of today's jjimjilbang, built their own deep heat-bathing cultures. The thread connecting all of them, steam and fire-heated stone for cleansing, healing, and community, long predates any clinical study.

  1. c. 2000 BCEFinnish savusauna and Mesoamerican temazcal traditions trace back roughly this far; heat bathing already ancient
  2. 100 CERoman thermae with hypocaust underfloor heating spread across the empire
  3. 1112Russian banya documented in Novgorod chronicles, of Finno-Ugric origin
  4. 1400Korean kiln saunas, forerunners of the jjimjilbang, in use by healers and monks
  5. 1500Ottoman hammam culture flourishes from Anatolia to North Africa
  6. 1936Finnish sauna showcased internationally; the word sauna enters global use
  7. 1990sTei and colleagues in Japan develop far-infrared Waon therapy for cardiac patients
  8. 2008Miyata, Tei and colleagues publish the multicenter Waon-therapy heart-failure study
  9. 2015Laukkanen et al. publish KIHD sauna-mortality findings in JAMA Internal Medicine
  10. 2016Randomized WAON-CHF trial (188 patients) reports improved ejection fraction and lower BNP
  11. 2017KIHD papers link frequent sauna to lower incident hypertension and lower dementia risk
  12. 2018BMC Medicine extension adds women, confirming the inverse cardiovascular-mortality association
  13. 2022-2023Small surrogate-endpoint RCTs report mixed results: benefit when sauna is combined with exercise, no vascular improvement in stable coronary-artery-disease patients

At a glance

Sudden cardiac death (4-7x/week vs 1x)
HR 0.37 (95% CI 0.18 to 0.75), Laukkanen 2015
All-cause mortality (4-7x/week vs 1x)
HR 0.60 (95% CI 0.46 to 0.80), Laukkanen 2015
Dementia / Alzheimer's (4-7x/week vs 1x)
about 66% and 65% lower risk, Laukkanen 2017
Typical Finnish protocol
79 to 100 C, 5 to 20 min/session, 4 to 7 sessions/week

What this entry does not yet cover

What follows is unfinished work on our side, not a finding about Sauna. A short entry is not a safe entry.

  • Cost and market. We have not documented what it sells for or who sells it.
  • Supply chain. We have not mapped where it is made.
  • Who uses it. We have not documented the user groups.
  • What could change. No forward-looking summary yet.
  • How it compares. We have not set it against the alternatives.
  • Children and teenagers. We have not checked what is known about younger people.

Sources