Sauna Research & Resources
The Science of Sauna and Heat Exposure
A library of peer-reviewed studies, scientific reviews, and selected expert conversations for people interested in learning more about sauna bathing and heat exposure.
Why Halsa built this page
We make sauna hats, towels, and bench pads, so we spend a lot of time reading the sauna literature. This page is where we keep track of the studies and conversations we find most useful — both the ones that support the popular narrative and the ones that complicate it.
We are not researchers. We are a small brand that thinks the science is interesting enough that it doesn’t need to be exaggerated. Nothing on this page is medical advice, and none of these studies evaluate a Halsa product.
Sauna bathing has been part of Nordic culture for centuries. In recent decades, researchers have also begun investigating how repeated heat exposure affects cardiovascular physiology, thermoregulation, inflammation, exercise adaptation, cognition, and other aspects of human health.
This library brings together peer-reviewed studies, scientific reviews, and selected educational conversations for people interested in learning more about sauna and heat exposure.
An Important Note About the Research
Sauna research is still developing.
Some of the most frequently cited findings come from long-term observational studies conducted in Finland. These studies have identified associations between sauna bathing habits and a number of health outcomes, but observational research cannot establish that sauna use itself caused those outcomes.
Clinical trials and experimental studies provide additional information about how the body responds to heat, but many are relatively small, short in duration, or investigate forms of passive heating that differ from traditional Finnish sauna.
For that reason, we distinguish between association, experimental evidence, and established cause-and-effect throughout this library.
The research discussed on this page concerns sauna bathing and heat exposure generally. It was conducted independently of Halsa, and none of it evaluates any Halsa product or demonstrates that any Halsa product produces a health outcome.
Featured Reviews
Clinical Effects of Regular Dry Sauna Bathing: A Systematic Review
Hussain J, Cohen M. — 2018 · Systematic review · Evidence-Based Complementary and Alternative Medicine
Researchers reviewed 40 clinical studies involving 3,855 participants examining repeated dry-sauna use.
The review identified research investigating possible cardiovascular, respiratory, metabolic, and other physiological effects. However, only 13 of the included studies were randomized controlled trials, and most individual studies were small (fewer than 40 participants).
Why it’s worth reading: One of the better broad overviews of the human sauna literature. The authors also make the limitations of the existing evidence clear.
Important context: The authors concluded that regular dry sauna bathing appears to have potential health benefits while emphasizing the need for larger and higher-quality studies.
PMID: 29849692 · DOI: 10.1155/2018/1857413 · Read on PubMed →
Sauna Use as a Lifestyle Practice to Extend Healthspan
Patrick RP, Johnson TL. — 2021 · Scientific review · Experimental Gerontology
This review examines the physiological response to sauna and heat stress, including thermoregulation, cardiovascular responses, heat-shock proteins, hormesis, and other proposed biological mechanisms. It also reviews observational and experimental research relating sauna use to cardiovascular health, cognition, and healthspan.
Important context: A narrative review rather than a randomized clinical trial. Useful for understanding proposed mechanisms and the broader scientific literature, though a narrative review necessarily reflects the authors’ framing.
PMID: 34363927 · DOI: 10.1016/j.exger.2021.111509 · Read on PubMed →
Non-Acute Effects of Passive Heating Interventions on Cardiometabolic Risk and Vascular Health
Hamaya R, et al. — 2025 · Systematic review and meta-analysis of RCTs · American Journal of Preventive Cardiology
This review analyzed 20 randomized controlled trials of passive heating lasting between two and 15 weeks. The interventions included sauna as well as hot-water bathing, hot yoga, local heating, and other forms of passive heat exposure.
Across the trials, researchers did not find statistically significant pooled improvements in most evaluated outcomes, including flow-mediated dilation, arterial stiffness, resting heart rate, heart-rate variability, fasting glucose, HbA1c, cholesterol, triglycerides, or C-reactive protein.
There was some evidence of reduced systolic blood pressure in subgroups receiving whole-body heat exposure and in populations with underlying cardiovascular risk, but the authors cautioned that the studies were heterogeneous and had important limitations.
Why it’s worth reading: An important counterbalance to observational sauna research. Long-term population studies have reported striking associations, while randomized trials have not yet demonstrated corresponding improvements across many intermediate cardiovascular markers.
PMID: 41049507 · DOI: 10.1016/j.ajpc.2025.101082 · Read on PubMed →
Cardiovascular Research
Association Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality Events
Laukkanen T, Khan H, Zaccardi F, Laukkanen JA. — 2015 · Prospective observational cohort · JAMA Internal Medicine
This influential Finnish study followed 2,315 middle-aged men (aged 42–60) for a median of 20.7 years.
Researchers examined associations between sauna frequency and duration and four outcomes: sudden cardiac death, fatal coronary heart disease, fatal cardiovascular disease, and death from any cause.
More frequent sauna use was associated with lower observed rates of each of these outcomes. Longer sauna sessions were also associated with lower rates of some cardiovascular outcomes. The associations remained after adjustment for multiple cardiovascular risk factors.
Important context: An observational study. It demonstrates an association, not proof that sauna caused the reduction in mortality. Sauna use may also correlate with other lifestyle, socioeconomic, social, or health characteristics that are difficult to completely account for statistically.
PMID: 25705824 · DOI: 10.1001/jamainternmed.2014.8187 · Read on PubMed →
Sauna Bathing and Cardiovascular Mortality in Men and Women
Laukkanen T, et al. — 2018 · Prospective observational cohort · BMC Medicine
Researchers followed 1,688 Finnish adults aged 53–74 (mean age 63; 51% women) for a median of 15 years.
Higher sauna frequency and greater total weekly sauna duration were associated with lower cardiovascular mortality. The study expanded upon previous Finnish research that had focused primarily on men.
Important context: The findings are observational. Although researchers adjusted for many cardiovascular and lifestyle factors, the study cannot establish that sauna exposure itself caused the difference in mortality.
PMID: 30486813 · DOI: 10.1186/s12916-018-1198-0 · Read on PubMed →
Sauna Bathing and Incident Hypertension
Zaccardi F, et al. — 2017 · Prospective observational cohort · American Journal of Hypertension
The study followed 1,621 Finnish men aged 42–60 who did not have hypertension at baseline.
During a median follow-up of 24.7 years, men reporting more frequent sauna use had a lower observed incidence of hypertension. Compared with once-weekly sauna use, the association was strongest among men reporting four to seven sauna sessions per week.
Important context: This does not demonstrate that sauna prevents or treats hypertension. It demonstrates a long-term statistical association in a specific Finnish population.
PMID: 28633297 · DOI: 10.1093/ajh/hpx102 · Read on PubMed →
Sauna Bathing and the Risk of Stroke: A Prospective Cohort Study
Kunutsor SK, et al. — 2018 · Prospective observational cohort · Neurology
Researchers followed 1,628 Finnish men and women aged 53–74 without a previous history of stroke.
During a median follow-up of 14.9 years, people reporting four to seven sauna sessions per week had a lower observed incidence of stroke than people reporting one sauna session per week. The association remained after adjustment for multiple cardiovascular and lifestyle factors.
Important context: This is an observational study. Although the study title uses causal language, cohort research of this type cannot establish that sauna use itself prevents stroke. Additional randomized research would be needed to demonstrate cause and effect.
PMID: 29720543 · DOI: 10.1212/WNL.0000000000005606 · Read on PubMed →
Acute Effects of Sauna Bathing on Cardiovascular Function
Laukkanen T, et al. — 2018 · Experimental study · Journal of Human Hypertension
Researchers studied 102 adults with at least one cardiovascular risk factor before and after a single 30-minute sauna session at approximately 73°C / 163°F.
Immediately following the sauna session, average systolic blood pressure decreased, average diastolic blood pressure decreased, and a measure of arterial stiffness decreased. Some effects persisted during the 30-minute recovery period.
Why this matters: Unlike long-term epidemiological studies, this experiment directly measured physiological responses before and after sauna exposure.
Important context: An acute physiological response does not establish that repeated sauna use prevents cardiovascular disease.
PMID: 29269746 · DOI: 10.1038/s41371-017-0008-z · Read on PubMed →
Eight Weeks of Finnish Sauna in Adults With Coronary Artery Disease
Debray A, et al. — 2023 · Randomized controlled trial · Journal of Applied Physiology
Forty-one adults with stable coronary artery disease were randomized either to maintain their usual lifestyle or to use a Finnish sauna four times per week for eight weeks. Sauna sessions lasted 20–30 minutes at approximately 79°C / 174°F.
Researchers found evidence that participants became more heat acclimated, including increased sweating capacity.
However, the sauna intervention did not significantly improve the primary measures of endothelial function, microvascular function, arterial stiffness, or systolic and diastolic blood pressure relative to the control group.
Why we include it: Good science includes studies that do not confirm a hypothesis. This randomized trial provides an important limitation on the idea that the strong cardiovascular associations seen in Finnish population studies necessarily translate into measurable short-term improvements in conventional vascular markers.
PMID: 37650138 · DOI: 10.1152/japplphysiol.00322.2023 · Read on PubMed →
Brain & Cognitive Health
Sauna Bathing Is Inversely Associated with Dementia and Alzheimer’s Disease in Middle-Aged Finnish Men
Laukkanen T, et al. — 2017 · Prospective observational cohort · Age and Ageing
Researchers evaluated sauna habits in 2,315 middle-aged Finnish men and followed them for a median of 20.7 years.
More frequent sauna use was associated with lower observed rates of both dementia and Alzheimer’s disease. The strongest association occurred among men reporting four to seven sauna sessions per week.
Important context: These findings are observational. The study does not establish that sauna prevents dementia or Alzheimer’s disease, nor does it establish a treatment for either condition.
PMID: 27932366 · DOI: 10.1093/ageing/afw212 · Read on PubMed →
Does Sauna Bathing Protect Against Dementia?
Knekt P, et al. — 2020 · Prospective observational cohort · Preventive Medicine Reports
Researchers studied 13,994 Finnish men and women aged 30–69 who were free from dementia at baseline.
Over a follow-up lasting as long as 39 years, certain sauna-use patterns were associated with a lower observed risk of dementia.
Why this study is useful: It examined a much larger and more diverse population than the earlier male-only Finnish cohort.
Important context: The authors themselves emphasized that additional studies are needed to verify the potential relationship, and the association was not consistent across all follow-up windows.
PMID: 33088678 · DOI: 10.1016/j.pmedr.2020.101221 · Read on PubMed →
Inflammation & Respiratory Research
Sauna Bathing and Systemic Inflammation
Laukkanen JA, Laukkanen T. — 2018 · Cross-sectional analysis · European Journal of Epidemiology
Researchers evaluated sauna habits and C-reactive protein (a common marker of systemic inflammation) in 2,084 Finnish men aged 42–60 without acute or chronic inflammation.
More frequent sauna use was associated with lower average C-reactive protein levels. The association remained after adjustment for several health and lifestyle factors.
Important context: This is a cross-sectional/observational association. It does not establish that sauna directly lowers chronic inflammation or treats inflammatory disease.
PMID: 29209938 · DOI: 10.1007/s10654-017-0335-y · Read on PubMed →
Sauna Bathing and the Risk of Respiratory Diseases: A Long-Term Prospective Cohort Study
Kunutsor SK, Laukkanen T, Laukkanen JA. — 2017 · Prospective observational cohort · European Journal of Epidemiology
Researchers followed 1,935 Finnish men aged 42–61 for a median of 25.6 years. More frequent sauna use was associated with a lower observed rate of hospital-diagnosed respiratory diseases, including pneumonia.
Important context: The study title uses causal language, but the study itself is observational. The findings should not be interpreted to mean that sauna prevents or treats respiratory infections, asthma, COPD, or pneumonia.
PMID: 28905164 · DOI: 10.1007/s10654-017-0311-6 · Read on PubMed →
Exercise, Performance & Recovery
Effect of Post-Exercise Sauna Bathing on the Endurance Performance of Competitive Male Runners
Scoon GSM, Hopkins WG, Mayhew S, Cotter JD. — 2007 · Small crossover intervention · Journal of Science and Medicine in Sport
Six competitive male distance runners completed three weeks of post-training sauna sessions and three weeks of a control training period. The researchers reported improvements in endurance performance following the sauna intervention, potentially related to increased blood volume.
Important context: This study involved only six athletes. The findings are interesting but far too small to establish a general performance recommendation.
PMID: 16877041 · DOI: 10.1016/j.jsams.2006.06.009 · Read on PubMed →
A Note for Competitive Athletes
The following study is most relevant to athletes training at a competitive level. For most sauna users, session timing around exercise is a lower-stakes decision.
Effects of Post-Exercise Sauna Bathing on Recovery of Swim Performance
Skorski S, et al. — 2019 · Randomized crossover study · International Journal of Sports Physiology and Performance
Twenty competitive swimmers and triathletes (national level or higher) completed an intensive training session followed by either sauna exposure or a placebo recovery condition. Swimming performance the following morning was measurably worse following the sauna condition.
Why we include it: Sauna is physiological stress, and more stress is not automatically better. Timing, hydration, training demands, and recovery requirements matter for competitive athletes with next-day performance obligations. For recreational sauna users not chasing a race the next morning, this study is less directly applicable.
PMID: 31869820 · DOI: 10.1123/ijspp.2019-0333 · Read on PubMed →
Effects of Post-Exercise Heat Exposure on Acute Recovery and Training Adaptations
Ahokas EK, et al. — 2025 · Systematic review · Sports Medicine — Open
This systematic review examined controlled trials involving whole-body heat exposure after exercise, including sauna and hot-water immersion. The review investigated both immediate recovery and longer-term training adaptations.
Why it’s useful: Provides a more comprehensive view than individual athlete studies and shows that the effects of post-exercise heat exposure depend on the protocol, timing, and outcome being evaluated.
PMID: 41032138 · DOI: 10.1186/s40798-025-00910-0 · Read on PubMed →
Safety & Tradeoffs
Sauna creates genuine physiological stress.
Heart rate rises, circulation changes, sweating increases, and fluid is lost. For most healthy adults, sauna bathing is generally well tolerated when used sensibly, but hotter and longer is not automatically better.
- Exit the sauna if you become dizzy, lightheaded, nauseated, weak, or otherwise feel unwell.
- Maintain appropriate hydration.
- Avoid sauna use while intoxicated or after substantial alcohol consumption.
- People with medical conditions, cardiovascular problems, abnormal blood pressure, impaired temperature regulation, or medications that affect circulation, hydration, or sweating should discuss heat exposure with an appropriate healthcare professional.
- Pregnant individuals, children, and people with specific health concerns should obtain individualized medical guidance rather than relying on general sauna protocols.
Seminal and Molecular Evidence That Sauna Exposure Affects Human Spermatogenesis
Garolla A, et al. — 2013 · Small longitudinal study · Human Reproduction
Ten healthy men used a Finnish sauna twice per week for three months at 80–90°C / 176–194°F for 15 minutes per session.
Researchers observed reductions in sperm count and motility and changes in other sperm-related measures after the sauna-exposure period. Importantly, the measured effects were reversible after sauna use stopped.
Important context: An extremely small study involving only ten men. Still, because testicular temperature can influence sperm production, men actively trying to conceive may wish to discuss frequent high-heat exposure with a qualified healthcare professional.
PMID: 23411620 · DOI: 10.1093/humrep/det020 · Read on PubMed →
Watch & Listen
Peer-reviewed research and expert commentary are not the same thing.
The following conversations can be useful for understanding the subject, but speakers may discuss theories, preliminary research, personal protocols, or interpretations that go beyond what has been firmly established in clinical trials. Halsa provides these resources for educational purposes and does not necessarily endorse every statement, recommendation, or interpretation made by the speakers.
Dr. Jari Laukkanen on Sauna Use and Long-Term Health Outcomes
FoundMyFitness with Dr. Rhonda Patrick — Episode #37
Dr. Jari Laukkanen is one of the principal researchers behind many of the long-running Finnish sauna cohort studies. In this conversation, Laukkanen and Patrick discuss the cardiovascular mortality research, blood pressure, sauna frequency and duration, dementia research, proposed biological mechanisms, sauna and exercise, heat exposure and heart rate, and practical limitations of the research.
Recommended because: It lets listeners hear directly from one of the researchers responsible for much of the sauna epidemiology discussed above.
Essentials: Benefits of Sauna & Deliberate Heat Exposure
Huberman Lab Essentials — Dr. Andrew Huberman
This episode provides a concise overview of deliberate heat exposure, including thermoregulation, heat-shock proteins, sauna frequency and duration, hormonal responses, mood, hydration, and sauna safety.
Important context: An educational podcast rather than a peer-reviewed scientific review. Some proposed mechanisms and protocol recommendations discussed in the episode are supported more strongly than others in the underlying research.
The Science & Health Benefits of Deliberate Heat Exposure
Huberman Lab — Dr. Andrew Huberman
A longer discussion of deliberate heat exposure covering cardiovascular physiology, hormones, heat-shock responses, mood, metabolism, sauna protocols, and safety.
Important context: Mechanistic plausibility does not necessarily establish long-term clinical benefit. Listeners interested in particular claims should consult the underlying research referenced in the episode.
AMA #16: Exploring Hot and Cold Therapy
The Peter Attia Drive — Dr. Peter Attia with Bob Kaplan
Peter Attia and Bob Kaplan examine the quality of evidence surrounding heat and cold exposure, including sauna.
The discussion is useful because it focuses heavily on distinguishing observational evidence from causal evidence and considers both possible benefits and limitations.
Common Questions About Sauna Research
Does research prove that sauna makes people live longer?
No.
Several long-term Finnish studies have found that people who used saunas more frequently had lower observed cardiovascular and all-cause mortality. Those findings are compelling, but they come primarily from observational studies. Observational research cannot prove that sauna exposure itself caused participants to live longer.
Randomized trials capable of directly testing decades-long mortality outcomes would be extremely difficult to conduct.
Does sauna prevent cardiovascular disease?
That has not been established.
Long-term Finnish cohort studies have found associations between frequent sauna bathing and lower cardiovascular mortality, hypertension, and stroke. Experimental studies also show that sauna causes measurable acute cardiovascular changes.
However, randomized evidence remains limited. A 2023 randomized trial of adults with stable coronary artery disease found heat acclimation but no significant improvement in several measures of vascular function or blood pressure after eight weeks of Finnish sauna use.
Does sauna prevent Alzheimer’s disease or dementia?
No clinical trial has established sauna as a way to prevent or treat Alzheimer’s disease or dementia.
Long-term Finnish observational studies have reported lower rates of dementia among certain groups of frequent sauna users. These findings are scientifically interesting and warrant additional research, but they should not be interpreted as proof of prevention.
What happens to the body in a sauna?
Heat exposure activates the body’s thermoregulatory systems. Common physiological responses include:
- increased skin blood flow
- increased sweating
- increased heart rate
- redistribution of circulation toward the skin
- changes in vascular tone
- fluid loss
- activation of cellular heat-stress responses
Repeated exposure can also produce heat acclimation. Researchers continue to investigate whether these responses contribute to longer-term health effects.
What are heat-shock proteins?
Heat-shock proteins are cellular proteins involved in maintaining and repairing other proteins during stressful conditions, including elevated temperature.
Heat exposure can activate cellular heat-stress pathways. Researchers are investigating how these pathways relate to aging, metabolic regulation, exercise adaptation, and neurobiology.
Demonstrating activation of a biological pathway is not the same thing as demonstrating that sauna prevents a particular human disease.
How many times per week should someone sauna?
There is no universally established evidence-based dose that is optimal for everyone.
Some Finnish observational studies found the strongest associations among people reporting four to seven sessions per week, but these groups were observed rather than randomly assigned. Those findings should therefore not be interpreted as a prescription that everyone needs to sauna four to seven times per week.
Heat tolerance, temperature, session duration, hydration, health status, and individual response all matter. Individuals with medical conditions should consult a qualified healthcare professional.
What temperature was used in the famous Finnish studies?
Much of the frequently cited Finnish research involved traditional Finnish sauna conditions rather than low-temperature infrared sauna. Typical temperatures in these studies were often around 70–90°C / 158–194°F.
This distinction matters because results from one form of heat exposure should not automatically be assumed to apply identically to every sauna type, temperature, or protocol.
Is infrared sauna equivalent to traditional Finnish sauna?
Not necessarily.
Both expose the body to heat, but they do so under different environmental conditions. Some studies specifically examine infrared sauna or Waon therapy, while many of the famous Finnish population studies involved traditional Finnish sauna.
Research findings should therefore be interpreted according to the type of heat exposure actually studied.
Is sauna a replacement for exercise?
No.
Sauna and exercise produce some overlapping physiological responses, including increased heart rate and circulation, but exercise produces numerous adaptations that passive heat exposure does not replicate.
Sauna should not be presented as a substitute for regular physical activity.
Does sauna “detox” the body?
Sweating is an important mechanism for regulating body temperature.
Small amounts of certain substances can be detected in sweat, but broad marketing claims that sauna “detoxifies” the body or removes clinically meaningful quantities of toxins are not established by strong evidence.
The liver, kidneys, gastrointestinal system, and other biological systems perform the body’s primary roles in processing and eliminating metabolic waste and foreign substances.
Does sauna improve sleep?
Many sauna users report relaxation and improved sleep after sauna use, and survey research has reported perceived sleep benefits. However, subjective reports are different from rigorous randomized sleep research.
It is reasonable to describe sauna as relaxing for many users. Strong claims that sauna has been proven to treat insomnia or sleep disorders would go beyond the current evidence.
Our Approach to Sauna Science
We think sauna research is interesting enough that it does not need to be exaggerated.
Our goal is to make worthwhile research easier to discover while remaining clear about what the evidence can — and cannot — tell us. Throughout this library:
“Associated with” means researchers observed a statistical relationship. It does not necessarily mean sauna caused the outcome.
“Experimental study” means researchers directly measured a response to heat exposure, but the result may still come from a small or short-duration study.
“Randomized controlled trial” generally provides stronger evidence for cause and effect, although the quality and size of individual trials still matter.
“Proposed mechanism” describes a biologically plausible explanation under investigation. A mechanism alone does not prove a health outcome.
We periodically update this library as better research becomes available. If you notice an error, an outdated citation, or a study we should consider adding, please let us know.
Educational & Medical Disclaimer
The information and third-party resources provided on this page are for general educational and informational purposes only. They are not medical advice and are not intended to diagnose, treat, cure, mitigate, or prevent any disease or medical condition.
The research discussed on this page concerns sauna bathing, passive heat exposure, or related physiological processes generally. The studies referenced were conducted independently of Halsa, did not evaluate any Halsa product, and their findings should not be interpreted as evidence that a Halsa product produces any particular health outcome.
Links to third-party studies, articles, podcasts, videos, and other resources are provided to help readers explore the subject. Inclusion of a resource does not mean that Halsa endorses every statement, interpretation, recommendation, or conclusion contained within it.
Scientific knowledge changes as new evidence becomes available. Readers should evaluate research in context and consult qualified healthcare professionals regarding individual health conditions, medications, pregnancy, fertility concerns, or questions about the suitability of sauna or heat exposure.
If you experience dizziness, lightheadedness, nausea, weakness, difficulty breathing, unusual discomfort, or other concerning symptoms during heat exposure, exit the sauna and seek appropriate medical care when necessary.
About Halsa
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