Sauna – A Path to Prolonging a Healthy Life

Sauna bathing appears to be genuinely beneficial, but not all claims hold up under close scrutiny.

Heat therapy has a long-standing history across cultures worldwide – including Finnish dry saunas, sweat lodges used by Native Americans, and Russian steam saunas known as banya. The use of saunas and their equivalents has existed for thousands of years and is deeply rooted in many cultures as a means of relaxation and social interaction.

Recently, popular media have turned their attention to sauna bathing, portraying it as a "longevity hack" and claiming a wide range of health benefits – from improved cardiovascular health to enhanced skin appearance. Given the vast diversity of these claims, the topic warrants a deeper, more comprehensive examination. Do current lines of evidence support the idea that sauna bathing is a cure-all for human longevity?

In this article, we will take a closer look at the strengths and limitations of the existing evidence behind many of the purported benefits, explore potential mechanisms of action, and conclude with practical considerations and recommended protocols for sauna use.

Inferring Causality from Observational Data

Most of the evidence supporting the wide range of purported benefits of sauna bathing comes from observational studies, particularly those conducted in Finland, where sauna use is a common part of life across socioeconomic groups. Because observational studies (with the exception of those employing Mendelian randomization) can only identify correlations between variables rather than causal relationships, we cannot be certain that many of the supposed "effects" of sauna use are actually caused by the sauna itself.

However, by evaluating correlational data in light of specific characteristics and within the broader context of scientific literature, we can estimate the likelihood that a true causal relationship exists. For this purpose, a set of principles known as the Bradford Hill criteria was developed to guide the inference of causality from observational data. Before we delve into the details of the evidence linking sauna use to various benefits, it is important to introduce these criteria, as we will return to them repeatedly when evaluating the reliability of epidemiological associations between sauna use and health.

The Bradford Hill Criteria include nine principles:

1. Strength: How large is the observed effect? The larger it is, the more likely it reflects a causal relationship.

2. Consistency: Are the findings consistent and reproducible across different studies and populations?

3. Specificity: How specific is the cause-effect relationship? If the exposure is associated with only one outcome (or the outcome with only one exposure), a causal link is more likely.

4. Temporality: Does the exposure precede the observed benefits?

5. Biological Gradient: Does the observed benefit show a dose-response relationship?

6. Plausibility: Is there a credible biological mechanism through which the exposure could produce the observed effect?

7. Coherence: How well do the observational data from human studies align with in vitro or in vivo laboratory findings?

8. Experiment: Are the conclusions supported by any interventional studies?

9. Analogy: Can the current evidence be compared to another, similar intervention with better-established effects?

   
   

If you compare epidemiology suggesting that smoking is a causal factor in lung cancer (and many other types of cancer) with the epidemiology examining the impact of various foods on cancer development, you can see why no reasonable person disputes the role of tobacco in cancer, while no such consensus exists about the link between specific foods and cancer. To be clear: evidence does not need to fulfill all nine criteria to provide a strong argument for causality. However, the more criteria a body of evidence meets, the greater confidence we can have in inferring a causal relationship. In other words, if the literature supporting a specific benefit of sauna bathing satisfies at least several of these criteria, it becomes more likely that the sauna directly causes the benefit rather than the association being purely coincidental. This is why we must keep these criteria in mind as we examine the existing evidence on the potential health effects of sauna use.

Evidence for the Benefits of Sauna Use

Research supports a range of benefits associated with sauna bathing, including improvements in cardiovascular (CV) health, reduced all-cause mortality, lower risk of dementia and Alzheimer’s disease, enhanced athletic performance, stress reduction, improved mental health, and better sleep. We will address these areas one by one below, considering evidence from epidemiological studies and, where available, from interventional and laboratory research.

Cardiovascular Health

Prospective cohort studies (non-randomized, it should be noted) have shown that more frequent sauna use reduces the risk of CV-related death and other serious cardiac events, even after adjusting for cardiovascular risk factors and potential confounding variables such as age, body mass index (BMI), and blood pressure. For example, in a 2015 study conducted on an all-male Finnish cohort over 20 years, Laukkanen et al. found a 63% reduced risk of sudden cardiac death among individuals who used the sauna 4–7 times per week compared to those who used it only once a week. They also reported a 48% reduction in coronary heart disease deaths and a 50% reduction in total cardiovascular mortality. A follow-up study by the same research team in 2018 found that the cardiovascular benefits persisted even when examining a mixed-gender Finnish cohort (n=1,688, 51.4% women) over 15 years, with those using the sauna 4–7 times weekly showing a 64% lower CV-related mortality compared to once-weekly users. Sauna use may also reduce the risk of stroke, as shown in another 15-year study among Finnish men and women, in which individuals who used the sauna 4–7 times per week had a 62% lower likelihood of experiencing a stroke compared to those using it only once a week.

Increasing the duration of individual sauna sessions may also contribute to improved CV health. In their 2015 study, Laukkanen et al. reported that, compared to those using the sauna for less than 11 minutes per session, individuals who spent more than 19 minutes had a 52% lower risk of sudden cardiac death, a 36% lower risk of fatal coronary heart disease, and a 24% lower risk of other fatal CV events.

Moreover, the work of Laukkanen and colleagues suggests that the apparent protective effect may be dose-dependent, as data from their 2015 study showed that individuals using the sauna 2–3 times per week had a risk level intermediate between once-weekly and 4–7 times weekly users, with risks of sudden cardiac death, fatal CHD, and fatal CVD showing a statistically significant decreasing trend with increasing sauna frequency. The researchers observed a similar trend in their 2018 follow-up study, although it did not reach statistical significance.

One proposed mechanism by which sauna bathing may confer CV benefits is its effect on endothelial function – specifically, improved vasodilation and reduced arterial stiffness. Experimental evidence shows that two weeks of sauna therapy in men with one or more coronary risk factors (hypertension, hypercholesterolemia, diabetes, obesity, smoking) led to improved brachial artery dilation following reactive hyperemia – a physiological response in which blood vessels dilate significantly after a brief interruption of blood flow, allowing more blood to reach the affected area – which is an indicator of endothelial health. Another study found that men and women with elevated CV risk who underwent a single 30-minute sauna session experienced improved arterial compliance, as measured by pulse wave velocity and left ventricular ejection time, two indicators of arterial stiffness. These changes were sustained throughout the 30-minute monitoring period after the sauna session.

Taken together, these findings provide compelling evidence that sauna use benefits cardiovascular health. The data consistently show strong and positive effects that also appear to be dose-dependent. Sauna use may be even more beneficial for CV health when combined with physical activity, as shown in one study indicating that combining sauna bathing with exercise led to better outcomes in terms of CV-related mortality (and all-cause mortality, see below) than sauna use alone. In addition, experimental evidence from studies on arterial compliance and vasodilation supports the proposed mechanisms by which sauna use may help reduce cardiovascular risk.

Dementia and Cognitive Health

Sauna use may also offer cognitive benefits. Another study by Laukkanen et al., published in 2017, showed that Finnish men who used the sauna more frequently (4–7 times per week) had a 66% lower risk of dementia compared to those who used the sauna only once a week, over a median follow-up of 20 years, after adjusting for several confounding variables. Similar results were observed specifically for Alzheimer’s disease (AD) – men who used the sauna 4–7 times weekly had a 65% lower risk than those who used it once weekly. Using the sauna 2–3 times per week was associated with an intermediate level of risk, although the differences in risk between this group and the 4–7 or 1-time-per-week groups did not reach statistical significance for either overall dementia or AD.

Given that women have a significantly higher lifetime risk of dementia – particularly Alzheimer’s disease – than men, it is important to assess how sauna use may affect dementia risk in cohorts that include women. A study involving 13,994 Finnish men and women found that those who used the sauna 9–12 times per month (~2–3 times per week) had a 53% lower risk of dementia during the first 20 years of follow-up, and an overall 19% reduction in risk over the full 39-year duration of the study, compared to those who either did not use the sauna at all or used it fewer than 4 times per month. Notably, this association was not influenced by adjustments for participant sex, suggesting that sauna use impacts dementia risk similarly in both men and women.

These findings are promising, but more studies are needed to determine the extent to which this effect applies to various forms of dementia or whether it is specific to Alzheimer’s disease.

All-Cause Mortality

Regular sauna use is also associated with reduced all-cause mortality (ACM). Evidence for this relationship comes primarily from the 2015 study by Laukkanen et al., mentioned above, which found a 40% reduction in ACM among men who used the sauna 4–7 times per week compared to those who used it once a week. Again, the risk reduction appears to be dose-related, as individuals who used the sauna 2–3 times per week had a risk level between the once-weekly and 4–7 times weekly groups. Given the strong effects on cardiovascular outcomes discussed earlier, it is likely that the reduction in ACM was partly driven by decreased CV-related deaths. Interestingly, however, unlike the findings on CV mortality, the duration of sauna sessions was not associated with ACM risk.

Frequent sauna use has also been shown to at least partially mitigate the elevated ACM risk associated with low socioeconomic status (SES) in Finnish men. Compared to high-SES individuals who used the sauna twice weekly, low-SES individuals who used the sauna twice weekly had a 35% higher risk of ACM. However, those with low SES who used the sauna 3–7 times per week had only a non-significantly higher ACM risk of 7% compared to high-SES individuals who used it twice weekly. Since most deaths (54%) in this study were not caused by cardiovascular disease, it is possible that the mortality risk reduction extends beyond CV health effects.

Exercise and Athletic Performance

Unlike most of the purported benefits listed above, which rely almost exclusively on epidemiological evidence, the proposed positive effects of sauna use on athletic performance – specifically as a recovery method – are also supported by interventional studies. For example, a randomized crossover study in male runners conducted by Scoon et al. found that 30 minutes of post-exercise sauna bathing led to a 32% increase in time to exhaustion – a commonly used endurance metric among runners and cyclists – compared to a control group using passive recovery. Another crossover study showed that post-exercise sauna use also helped reduce muscle soreness and preserve muscle function. Compared to those who used passive recovery, basketball players who used the sauna for recovery reported less subjective muscle soreness after training and experienced a smaller reduction in countermovement jump height (a test of lower-body explosive power) 14 hours after resistance training.

One mechanism believed to underlie this benefit is increased plasma volume, which is associated with better muscle perfusion and improved cardiac function. In the aforementioned study by Scoon et al., sauna bathing led to a 7.1% increase in plasma volume compared to the control group that did not engage in any specific recovery protocol.

The heat-related increase in plasma volume likely stems from adaptations triggered by temporary water loss during sauna use. This assumption is supported by findings that dry saunas (which lead to greater fluid loss through sweating than steam saunas) cause greater reductions in plasma volume, and that mild dehydration before heat exposure promotes a subsequent increase in plasma volume. This decrease in plasma volume is followed by an increase that becomes evident within 24 hours of sauna use. One study examining exercise in hot environments showed that this increase occurs primarily during the first day but continues over the first week, peaking around day eight of continuous heat exposure. A similar effect was observed in a sauna study showing that five consecutive days of sauna use led to sustained increases in plasma volume, indicating that these changes are not merely transient when heat exposure is regular.

A study by Rissanen et al. also found that plasma volume increases depended on the type of exercise preceding sauna use. Participants who used the sauna after endurance or combined endurance-resistance training experienced increased plasma volume 24 hours post-sauna compared to controls, whereas this effect was not seen in those who used the sauna after resistance-only training. This suggests that the beneficial effects of sauna as a recovery tool may be specific to endurance exercise. Furthermore, it appears that the performance benefits of sauna are tied to its use after training, not before, as 30 minutes of sauna use prior to exercise led to worse results in endurance tests (leg press and bench press) and strength (one-repetition maximum in leg press) compared to when no pre-exercise sauna was used.

Sauna use has also been linked to improvements in VO₂ max and bone density, although these claims are based on less robust evidence. For example, Kirby et al. demonstrated a modest benefit to VO₂ max in runners, but the effect did not reach statistical significance. Regarding bone density, a study by Toro et al. found that in a group of 23 young men, twelve sauna sessions led to a statistically significant improvement in bone mineral content and bone density compared to a non-sauna control group. However, it remains unclear whether this is a real and reliable effect, as the benefit was small and observed only in the left leg (whole-body and right leg measures showed no significant difference between groups).

In summary, there is convincing evidence supporting sauna use as a recovery strategy after endurance training, whereas other performance-related claims are not sufficiently substantiated. It should also be noted that, despite the controlled and interventional nature of some of these studies, placebo effects may have contributed to the observed benefits, as participants were aware of whether they were assigned to the sauna recovery group.

Mental Health

One of the most widely held beliefs about sauna bathing and other forms of whole-body heating is their potential benefit for mental health. However, research in this area remains very limited.

A small study conducted in Japan with 45 healthy volunteers suggested that sauna use may reduce anxiety and improve mood and depressive symptoms. However, due to the absence of a control group, it is not possible to confidently determine whether these improvements were the result of a placebo effect. Effects on depression were also evaluated in a randomized pilot interventional study of medically stable patients with depression, in which two hyperthermic baths per week (40°C for 30 minutes) over two weeks resulted in a 3.14-point reduction in Hamilton Depression Rating Scale scores (out of a maximum of 52 points) compared to a control group receiving a “sham” procedure. Although this study did include a control group, the placebo effect may have played a substantial role, since it was not possible to blind participants to whether they actually received a hyperthermic bath. Moreover, it is unclear whether these results can be generalized to sauna use.

Additionally, a prospective cohort study in Finland found an inverse association between sauna frequency and the incidence of psychotic disorders. Among men with no history of psychosis (or prior antipsychotic treatment), those who used the sauna 4–7 times per week had a 79% lower risk of developing psychosis during a 25-year follow-up compared to those who used the sauna once per week. This relationship remained consistent across different statistical models adjusting for various sets of confounding variables. However, among men who used the sauna 2–3 times per week, no significant difference was found compared to once-weekly users, and no further data are available to suggest a causal relationship.

Given the current lack of effective and widely accessible strategies for preventing and treating psychosis, depression, and anxiety, sauna use may represent a promising option for individuals experiencing or at risk for these conditions. The association between sauna use and lower risk of psychosis is relatively strong, and some data also suggest a connection with reduced depression and anxiety. At this time, however, we lack compelling evidence that these associations represent effects caused by sauna use. (For example, the observed effects could be due to a confounding variable such as social interaction, since sauna bathing often occurs in a communal setting. Alternatively, it is possible that individuals with psychosis avoid saunas because they prefer to spend less time around others – which would imply a reverse causal relationship.)

Thus, while there is currently too little evidence to conclude definitively that sauna use directly improves mental health, the possibility certainly exists – and may be worth exploring for individuals with these conditions, particularly when effective alternative treatments are lacking.

Sleep

Circadian rhythms in body temperature during and around sleep suggest that interventions targeting body temperature changes may improve sleep quality. As the body prepares for sleep, core temperature begins to drop and continues to decline throughout most of the night, until about an hour or two before waking, when it begins to rise again. The steeper this temperature drop before bedtime, the faster we fall asleep and the better the sleep quality. Whole-body heating may also help reduce insomnia—for example, in a study where older women took a hot bath 90 minutes before bedtime, researchers observed improved sleep continuity and an increase in slow-wave sleep. These women also subjectively rated their sleep as “deeper” and “more refreshing.”

Although these findings have not yet been directly replicated with sauna use, it is reasonable to expect that this form of whole-body heat exposure would have a similar effect on sleep as a bath or shower. In fact, in one survey-based study, 83.5% of respondents reported that sauna bathing improved their sleep.

Pain

Sauna use has been reported to alleviate various types of pain, including headaches, back pain, and other forms of chronic pain. In a randomized controlled trial, individuals with chronic tension-type headaches were randomly assigned to a sauna treatment group (sauna use plus pain management advice) or a control group (pain management advice only). After eight weeks of treatment, the sauna group reported a 1.27-point reduction (on a 0–11 scale) in subjective headache intensity compared to the control group. However, the study found no benefit regarding the duration of headaches, despite the significant improvement in pain intensity ratings. It is important to emphasize that sauna use in this study was employed as a preventive measure rather than a treatment method – since sauna bathing may worsen headaches in some cases, conditions for sauna use in the context of headaches must be carefully controlled.

Regarding back pain, five consecutive days of twice-daily dry sauna sessions led to a 2-point reduction in lower back pain on the verbal numeric pain scale (0–10) and a 4-point reduction in disability score on the Oswestry Disability Index (0–50). This effect is analogous to the better-studied relief effect of thermal baths – for example, a meta-analysis of randomized trials found that thermal baths led to an average reduction in back pain of 16.07 points on a visual analog pain scale and an average improvement in lumbar function of 7.12 points as measured by the Oswestry Disability Index, compared to control subjects who did not use thermal baths.

Another study involving individuals with somatoform pain disorder showed that four weeks of sauna bathing combined with cognitive behavioral therapy (CBT), rehabilitation, and movement therapy resulted in slightly better outcomes in pain behavior assessments (based on complaints, medication requests, etc.) than in those receiving CBT, rehabilitation, and movement therapy without sauna use, although the results did not reach statistical significance. However, sauna addition did lead to a higher rate of return to work. Given that both groups showed significant improvement, it can be inferred that the other components of this tri-modal rehabilitation intervention also contributed to the overall effect, suggesting that sauna bathing is only one possible pathway to pain improvement.

There are, however, forms of chronic pain for which the evidence regarding sauna use is mixed. In particular, one study of individuals with rheumatoid arthritis and ankylosing spondylitis reported short-term reductions in pain and stiffness following sauna use, while an older study in a similar population reported worsened pain symptoms.

Chronic pain is widespread and can be highly debilitating, which increases interest in sauna use as a potential therapeutic modality. However, given the modest effects and conflicting evidence, more studies are needed to draw definitive conclusions about the impact of sauna use on pain conditions. Sauna use may offer modest benefits for pain management in some cases, but other, better-established methods (e.g., medication, cognitive behavioral therapy, movement therapy) may be more effective.

Stress

Popular media often describe sauna use as an excellent way to relieve stress or enhance stress resilience, and these perceived benefits are frequently cited as primary reasons why people use saunas. Moreover, social interaction – which is known to influence stress – was reported as a motivating factor for sauna use by 85% of participants in one study. Although there is currently limited direct evidence supporting sauna effects on stress, sauna bathing influences several physiological responses that relate to how we experience stress. For example, the reductions in heart rate and blood pressure that occur after sauna use may partly explain the calming effect that many people report. During acute stress, heart rate and blood pressure temporarily rise due to activation of the sympathetic nervous system, and the opposite reaction (a drop in heart rate and blood pressure) may induce a sense of "unwinding."

Reducing stress benefits many bodily systems, including – but certainly not limited to – the cardiovascular and immune systems. Therefore, stress reduction can have a significant impact on health that extends beyond the immediate perception of being less stressed.

Commonly Claimed but Poorly Supported Benefits

Two frequently cited benefits of sauna use – “detoxification” and enhanced immune function – currently lack strong scientific backing, though they merit brief mention.

Saunas are often considered a means of promoting detoxification, especially regarding heavy metals like mercury or lead, due to their role in increasing sweat output. Sweating is indeed one of the main routes through which the body eliminates heavy metals. However, it is unclear whether excessive sweating induced by sauna use leads to significantly greater heavy metal excretion or merely increases sweat volume with a corresponding decrease in metal concentration per unit of sweat. Furthermore, although research generally supports sweating as a strategy for eliminating toxic metals following high exposure (acute or chronic), there is little evidence that increased sweating meaningfully reduces heavy metal levels in the average person.

Enhanced immune function has also not been clearly demonstrated, although stress reduction associated with sauna use (as discussed above) may offer some benefits to the immune system. In addition, sauna use has been observed to increase the counts of white blood cells, lymphocytes, neutrophils, and basophils, which could indicate immune activation. However, it is uncertain whether this response provides any long-term benefit to immune function.

A summary of evidence-based sauna benefits is shown below in Figure 1.

Figure 1: Benefits of Sauna Use Ranked by Magnitude of Effect and Certainty of Evidence. The magnitude of effect and certainty of evidence for each benefit are rated relative to the magnitude and certainty of the other sauna-related benefits. (Image adapted from www.peterattiamd.com)

A Broader Perspective on the Evidence

With the exception of a few small experimental studies, most of the evidence discussed above is derived from observational data, which we can interpret in the context of the Bradford Hill criteria for each specific sauna-related benefit (Table 1).

Table 1: Sauna Benefits Assessed According to the Bradford Hill Criteria*

*A 0-4 scale was used, with 0=negative/unconvincing data (data support no effect of sauna) and 4=very convincing data (data strongly support an effect of sauna). Y/N denotes yes/no for the temporality criterion. Dash (-) denotes a criterion for which there is little to no supporting data. (adapted from www.peterattiamd.com)

These effects do not exist in isolation – for example, cardiovascular effects likely influence the observed reduction in all-cause mortality, as discussed earlier. Therefore, it is worth pausing to consider the sauna literature as a whole, acknowledge how different domains may interact, and identify limitations that apply universally.

Many of the potential benefits of sauna use are interconnected. Improvements in circulation and cardiac function, considered key mechanisms in enhancing athletic performance, are clearly closely linked to cardiovascular health. Better sleep, reduced stress, and a healthier cardiovascular system are all associated with a lower risk of dementia. Pain reduction likely improves both sleep quality and mental health. Thus, although the evidence supporting each individual effect may be relatively limited, the consistency in the overall direction of these related outcomes means that the total body of sauna evidence is stronger than the sum of its parts. This increases our confidence that sauna use likely causes at least some of these benefits, even as it complicates efforts to isolate each effect and determine whether it is a direct result of sauna use or a correlated variable.

We must also be cautious of the potential influence of the healthy user effect in the sauna benefit literature. Many of the strongest epidemiological studies have been conducted in Finland, where regular sauna use is common across socioeconomic strata. Estimates suggest that 60–90% of Finns use a sauna at least once per week, which introduces two possible sources of bias: (i) people who do not use saunas or use them much less frequently may do so because they were medically advised against it, and (ii) individuals with the highest sauna use frequency may be substantially more health-conscious – similar to how people in the U.S. who exercise more than average are generally more health-oriented. If either of these scenarios holds true, then the benefits associated with sauna use – or the absence of benefits at lower frequencies – may be partially or entirely due to other healthy lifestyle behaviors (e.g., better diet, more physical activity) rather than sauna use itself.

Furthermore, in Finnish culture, sauna use is an important aspect of social life, and the claimed benefits may reflect the health advantages of socialization – either in addition to or instead of the sauna itself. This may be especially relevant to findings related to dementia, stress, and depression, as social connection – or its absence – plays a significant role in all three domains.

Outside of Finland, sauna use is likely an even stronger indicator of the healthy user effect. In countries where saunas are less common and less accessible, individuals who actively seek out sauna use are more likely to come from higher socioeconomic backgrounds and/or have an exceptionally high motivation for health maintenance. While many studies on sauna use adjust results for various health variables to mitigate the healthy user effect, no statistical adjustment can account for all potential confounding factors.

Still – particularly regarding cardiovascular effects and enhanced post-exercise recovery – the evidence supporting true sauna benefits is strong enough to conclude that a causal relationship is likely. The supporting literature holds up under several of the Bradford Hill criteria, such as consistency, strength, biological gradient, and others (see Table 1), reducing the likelihood that these associations are significantly misinterpreted. However, one criterion warrants closer examination: plausibility. We have briefly addressed this in relation to certain specific claims, but to fully understand and evaluate sauna effects, we must deepen our understanding of how the body responds to heat stress.

What Is Thermoregulation?

Before diving into the potential mechanisms behind the apparent effects of sauna bathing, we must first understand the concept of thermoregulation – specifically, why and how our bodies maintain a stable internal temperature of around 37 ± 0.5 °C.

This narrow temperature range is essential for the function of enzymes – proteins that catalyze nearly all biochemical processes in the body, from RNA synthesis (and subsequent protein synthesis) to energy production. While the biology of enzyme function is complex, most enzymes in the human body follow a roughly similar performance curve: low activity at lower temperatures, optimal function around 37 °C, and a steep decline in activity at higher temperatures. In fact, at temperatures above 40 °C, not only do enzymes denature, but so do other proteins in the body (which make up nearly all cellular structures and processes) – proteins unfold and lose their function. Above this internal temperature threshold, human life is no longer possible. For this reason, thermoregulation is a highly robust and evolutionarily conserved component of human biology.

Temperature homeostasis – the maintenance of body temperature within the 37 ± 0.5 °C range – is primarily regulated by an area of the brain called the hypothalamus (specifically, the preoptic area of the hypothalamus). This region receives signals from thermoreceptors in nerve endings throughout the skin (i.e., peripheral temperature sensors), as well as from the spinal cord and internal organs (i.e., central temperature sensors). Any deviation in temperature is detected by these receptors and transmitted to the hypothalamus, which then activates thermoregulatory mechanisms in the body.

This leads to one of two outcomes: heat production or heat loss.

Heat production occurs via several mechanisms. Activation of the sympathetic nervous system causes vasoconstriction – the narrowing of blood vessels near the skin’s surface (cutaneous arterioles) – which redirects blood away from the skin and reduces heat loss to the environment. Increased release of catecholamines (especially norepinephrine from the adrenal glands) and thyroid hormones, both stimulated by the hypothalamus, elevates metabolic activity and thus heat production. The motor center in the posterior hypothalamus is activated to increase muscle activity, which generates heat and results in the familiar shivering response when cold. Piloerection (raising of body hairs) helps trap air at the skin’s surface, retaining warm air close to the body. The brain also initiates behavioral responses to retain warmth: adding layers of clothing, increasing movement to generate heat (e.g., tapping fingers or shivering), and assuming a closed body posture to minimize heat loss.

Heat loss, the process relevant to sauna use, employs many of the same strategies in reverse. Inhibition of the sympathetic nervous system leads to vasodilation – the widening of blood vessels near the skin’s surface – allowing a greater volume of blood to flow near the skin and increasing heat dissipation. Reduced release of catecholamines and thyroid hormones lowers metabolism and thus heat production. Activation of cholinergic neurons responsible for sweat gland function leads to increased sweating and heat loss through evaporation. The brain also initiates behavioral changes to promote cooling: removing clothing to reduce heat retention, ceasing movement to limit heat production, and assuming an open body posture to increase surface area for heat loss.

Hormesis

How, then, might sauna bathing exert positive effects through its influence on thermoregulation? The answer likely lies in a phenomenon known as hormesis.

Hormesis is an adaptive cellular response to exposure to something harmful. Occasionally – in small doses or for short durations – such harmful stimuli can be beneficial. Consider the universal human experience of fever during infection. Viruses and bacteria thrive at normal body temperature. By temporarily raising body temperature, the immune system tries to create a hostile environment for these pathogens. Once viruses or bacteria are detected, the hypothalamus increases the body’s temperature set point to make the environment less favorable to the invaders, while simultaneously activating mechanisms that protect the proteins and cells in our bodies. The result is that pathogens are eliminated while our own tissues are safeguarded. A key feature of fever associated with acute illness, however, is that elevated body temperature is only beneficial in small, controlled doses. If body temperature remains high for too long, serious consequences may occur – including dehydration, protein denaturation, organ damage, and ultimately death.

The fact that short-term elevated body temperature can destroy pathogens while preserving our own cellular integrity raises another question: can temporary increases in body temperature benefit us even in the absence of pathogens?

In the case of sauna use, temporary heating in the absence of infection not only raises body temperature (core temperature increases by 1–3 °C; skin temperature by 6–8 °C), but also affects heart rate (which rises to 100–150 beats per minute), cardiac output (increasing by 60–70%), and blood pressure (systolic pressure rises by about 15 mmHg). It is reasonable to expect that we might derive benefits that go beyond the fever response, especially since these changes closely resemble the physiological shifts that occur during moderate-intensity exercise.

In response to this “heat stress,” our cooling mechanisms are activated. We begin to sweat, vasodilatory changes occur that widen blood vessels and facilitate greater heat dissipation. Catecholamines (and other hormones) released to cool the body in response to rising temperature may, in fact, trigger mechanisms responsible for many of the benefits described earlier. But how and why do these hormones deliver such effects?

Biological Mechanisms Behind the Effects of Sauna Use

Exposure to high temperatures, which activates the sympathetic (“fight or flight”) nervous system, leads to increased heart rate, blood pressure, and sweating – but it also triggers several hormonal changes.

Although heat exposure (e.g., in sauna use) influences a wide range of hormones, this review will focus on four hormones that are most likely related to the reported benefits of sauna use: norepinephrine (a catecholamine), beta-endorphins, growth hormone (GH), and prolactin.

Hormonal Effects

Norepinephrine is rapidly released in response to biological stress, and its levels rise during heat stress in the sauna. While norepinephrine levels begin to drop quickly after sauna use ends, they remain elevated for at least an hour afterward. It is possible that these elevated levels persist even longer, as the final measurement in the referenced study was taken one hour post-sauna. The other three hormones – beta-endorphins, prolactin, and growth hormone – show a similar pattern: a dramatic rise during sauna exposure followed by a gradual decline after it ends.

Mechanistically, norepinephrine is the primary hormone responsible for the physical sensations associated with sauna use, including increased heart rate and blood pressure. These effects result from norepinephrine-induced vasoconstriction in deeper blood vessels and visceral circulation. At the same time, vasodilation occurs in the skin to allow heat dissipation through sweating. This redistribution of blood flow is complex. During sauna exposure, the overall vascular response is a combination of central vasoconstriction and peripheral vasodilation. Norepinephrine also promotes the production of heat shock proteins, reactive oxygen species, and brain-derived neurotrophic factor (BDNF), all of which may contribute to many of the benefits discussed earlier.

Beta-endorphins are also released during heat stress in the sauna. Endorphins are the body’s natural pain-relieving compounds, and heat-induced beta-endorphin release may lead to feelings of well-being or reduced stress through binding to mu-opioid receptors in the brain. Heat stress can also increase the release of dynorphins, which modulate the endorphin system. Dynorphins act via kappa-opioid receptors and may partly explain the discomfort sometimes felt during sauna use. Over time, however, dynorphin activity leads to upregulation of opioid receptors, which effectively enhances the body’s ability to respond to beta-endorphins when they are released. These two mechanisms may explain how the endorphin pathway triggered by sauna use contributes to a range of benefits: stress reduction, improved mental health, pain modulation (especially headache relief), and potentially enhanced athletic performance (via increased pain tolerance or reduced perception of pain).

Growth hormone (GH), also released in response to heat stress, may explain additional sauna-related benefits. GH plays a key role in post-exercise recovery, particularly through its effects on tissue repair, and may also support mental health and cognitive function – there is evidence that GH supplementation in individuals with GH deficiency improves mood and cognitive performance. GH may also contribute to some of the cardiovascular benefits observed with exercise by increasing reactive oxygen species, which can promote endothelial health (see below).

A less well-supported but still interesting hormone is prolactin. Although prolactin is commonly associated with pregnancy, it also increases in response to heat stress. Notably, prolactin may support the health and function of the brain’s white matter and could therefore play a role in sauna-related benefits for mental health and dementia prevention.

Heat Shock Proteins, Brain-Derived Neurotrophic Factor, and Reactive Oxygen Species

As noted above, norepinephrine release leads to increased production of heat shock proteins (HSPs, especially HSP-70), which play a critical role in protecting the body’s proteins from damage caused by unfolding, misfolding, and aggregation. These proteins temporarily bind to and “chaperone” other proteins, especially during periods of cellular stress. HSPs can also repair or resynthesize proteins that have already been damaged. It is well established that heat stress significantly increases HSP expression in humans, providing a plausible mechanistic role for these proteins in the benefits of sauna use.

HSPs may be particularly important for post-exercise recovery due to their effects on muscle proteins. HSP synthesis occurs over several hours, peaking approximately 3–5 hours after heat exposure and declining within 8 hours, suggesting that the effects of HSPs may persist for a relatively long period.

The main regulator of HSP production, called heat shock factor 1, is also known to increase the production of brain-derived neurotrophic factor (BDNF), a protein believed to play a key role in mental health and cognitive function. Sauna use has indeed been shown to elevate blood levels of BDNF. Mechanistically, BDNF promotes neuroplasticity and supports the survival and growth of neurons. This function may underlie several of the proposed benefits of sauna use, including improved mental health and dementia prevention.

Another effect of increased sympathetic nervous system activity is the production of reactive oxygen species (ROS). During heat stress and activation of this branch of the nervous system, oxygen demand increases in multiple tissue types. As the body increases respiration and takes in more oxygen, it also begins producing more ROS. In addition, elevated growth hormone levels following sauna use may further support ROS generation. While chronically elevated ROS levels are known to increase oxidative damage to DNA and other cellular structures, small doses of ROS are considered beneficial.

Although evidence is not yet conclusive, this is one mechanism through which sauna-induced cardiovascular benefits may be explained. There is evidence from patients with chronic heart failure suggesting that dysregulated ROS production is a hallmark of the condition. Furthermore, inhibition of nitric oxide synthesis – a key contributor to ROS formation – leads to increased arterial stiffness, offering mechanistic evidence that ROS play a role in endothelial health. Taken together, repeated low-dose exposure to ROS from sauna use may enhance endothelial function and provide protective effects in multiple aspects of cardiovascular and cerebrovascular health.

All of these mechanisms (hormonal, HSPs, ROS) are summarized in Figure 2.

Figure 2: The mechanisms underlying sauna benefits include processes resulting from transient but reversible increases in norepinephrine, prolactin, growth hormone, heat shock proteins, Brain-Derived Neurotrophic Factor (BDNF), Reactive Oxygen Species (ROS) and beta-endorphins. (adapted from https://peterattiamd.com)

Although sauna bathing is also associated with reduced inflammation, this benefit may not be specific nor strongly support any particular claimed effect. Of course, reducing inflammation benefits health across a wide range of areas. However, it appears that an improved inflammatory profile is not a specific or dominant mechanism underlying any of sauna bathing’s particular benefits.

It is also worth noting that while cortisol is often cited as a mechanism explaining sauna benefits, the evidence supporting this claim is not convincing. Many studies have investigated cortisol release in response to sauna use, and the results are mixed—with several studies finding no significant change.

Naturally, regardless of the physiological mechanisms involved, we can only derive benefits from sauna use if we understand its practical applications. Up to this point, we have explored the question of “why.” Now it is time to focus on the questions of “who,” “what,” “when,” “where,” and “how.”

How to Use a Sauna Effectively

There are five key elements to consider when using a sauna:

• the type of sauna,

• the sauna temperature,

• the ideal session duration,

• the optimal timing of sauna use,

• the optimal frequency of sauna bathing.

Types of Sauna

There are three main types of sauna: infrared sauna, steam sauna, and dry sauna. Infrared saunas emit infrared light, which we perceive as heat once it is absorbed by the skin. In contrast, steam saunas generate heat by heating water to produce compressed steam, which is then released into an enclosed space. Dry saunas are heated using air generators, hot stones, or other mechanisms.

Although the heating mechanisms differ, all types of saunas likely offer similar benefits if sufficient temperature, duration, and frequency of use are achieved. This also applies to other forms of heat exposure, such as hot tubs, thermal baths, hot showers, or even simply standing outside on a hot day, which could induce a comparable level of heat stress. While most studies referenced in this review used dry saunas (15 studies), there were also studies on infrared saunas (4), thermal baths (3), steam saunas (2), comparative heating methods (2), and studies without a specified sauna type (2). Many of the reported benefits have been observed across various heating modalities. For example, pain relief has been reported with both dry saunas and thermal baths. Reduced cardiovascular mortality was observed in dry sauna users, but some underlying mechanisms linked to cardiovascular benefits were also documented in infrared sauna studies. Given the overlapping effects across heating methods, it is reasonable to assume that similar health benefits can be achieved with non-dry saunas if a comparable degree of heating and exposure duration is met.

However, increased caution is warranted when using infrared and steam saunas. Infrared saunas vary in wavelength, intensity, and light source placement, which may affect the consistency and extent of body heating. Steam saunas may more easily induce overheating at the same session duration compared to dry saunas, likely due to reduced evaporative cooling caused by high humidity.

Older individuals using infrared or steam saunas—where safe temperature ranges are not as well established—should exercise particular caution, as the body's ability to regulate temperature declines with age. This caution also applies to anyone with impaired thermoregulation due to health conditions.

Sauna Temperature

Regarding temperature, the vast majority of studies cited above used dry saunas operating at temperatures between 80°C and 100°C. Any temperature significantly above this range may pose safety risks, and since lower temperatures have not been adequately studied, it is uncertain whether they provide meaningful health benefits.

In steam saunas, both body temperature and heart rate increase more rapidly than in dry saunas, even at lower ambient temperatures. Therefore, it is important to ensure that skin temperature increase remains within the safe range of +6–8°C. Most guidelines for steam saunas recommend ambient temperatures between 38°C and 49°C. Due to reduced ability to cool the body through sweating in a humid environment, lower temperatures are sufficient to induce comparable heat stress. Monitoring skin temperature may therefore be a helpful indicator of adequate heating in steam saunas, especially since humidity levels can vary between models. A similar recommendation applies to infrared saunas. Since different models may use different light wavelengths, each affecting the body differently, it is best to follow the manufacturer’s temperature guidelines for IR sauna use.

Duration of Sauna Sessions

In terms of duration, most studies utilizing sauna bathing as an intervention prescribed sessions lasting between 15 and 30 minutes. While this may represent an ideal target for long-term use, it is likely not feasible for beginners. In dry saunas, it is recommended that novices start with shorter sessions (e.g., 5 minutes) and gradually increase the duration up to 20 minutes, taking care not to exceed 30 minutes due to the heightened risk of dehydration. For steam saunas, much shorter durations are advised, with many recommendations suggesting a maximum of 10 to 20 minutes. In infrared saunas, the studies mentioned earlier achieved positive outcomes with sessions ranging from 15 to 30 minutes. Just like with temperature—which can cause adverse effects if not kept within an appropriate range—session duration must be carefully monitored to avoid overheating and serious consequences.

Timing of Sauna Use

The ideal timing of sauna use depends primarily on the goal a person hopes to achieve.

For those aiming to improve sleep quality, the optimal time is one to two hours before bedtime. As previously explained, the steeper the decline in body temperature before falling asleep, the better the sleep quality. Entering a sauna shortly before bed is an easy way to enhance this temperature drop.

For those interested in improving athletic performance, sauna use is likely most beneficial after exercise, as it can take advantage of mechanisms such as the upregulation of heat shock proteins (HSPs) and growth hormone secretion.

A recent study suggests that for individuals using saunas to improve cardiovascular health, combining sauna use shortly after physical activity may enhance benefits beyond those of exercise alone. Although the studies investigating cardiovascular benefits did not evaluate whether the time of day influences the observed outcomes, it is likely that the underlying biological mechanisms are not time-dependent—though this remains an open question for future research.

Frequency of Sauna Use

As for frequency, the studies reviewed suggest that more is better. Individuals who used the sauna four or more times per week consistently showed the greatest benefits. Although the difference was not always statistically significant, those using the sauna two to three times weekly experienced greater benefits than those using it only once a week.

However, it is important to note that using the sauna multiple times in a single day—although shown to increase growth hormone and not necessarily acutely dangerous—significantly raises the risk of dehydration and is generally not recommended. Moreover, while daily sauna use may yield greater benefits than weekly use, if the higher frequency comes at the expense of other health-promoting activities, particularly exercise, sauna use should be considered a lower priority.

A summary of the optimal sauna parameters is presented in Table 3 below.

*Recommendations for steam and infrared sauna use are based on safety rather than effectiveness, as few studies have been conducted using steam and infrared saunas.  †The temperature and duration recommendations for infrared saunas vary depending on the model being used. (adapted from https://peterattiamd.com)

Risks Associated with Sauna Use

Common side effects of sauna use include dehydration, dizziness, and headaches. However, these symptoms are typically short-term and tend to resolve on their own after leaving the sauna.

Occasionally, injuries from falls can occur in the sauna, most often due to slipping, dizziness, or fainting (one Finnish study reported approximately twelve sauna-related injuries per year in a single hospital). Two simple preventive measures to reduce the risk of slipping or dizziness-related falls are to wear anti-slip sandals or footwear and to maintain adequate hydration.

Certain groups of people should avoid sauna use altogether, particularly those with uncontrolled cardiovascular disease (e.g., angina pectoris, heart failure, recent heart attack), as they may not tolerate the increases in blood pressure (up to +15 mmHg systolic), heart rate (up to 100–150 bpm), and cardiac output (increased by 60–70%) that accompany sauna use. For individuals with controlled cardiovascular disease or other cardiovascular risk factors, consulting a doctor before using a sauna may be advisable. Nevertheless, sauna use is likely to be safe and well-tolerated in these cases and may even offer significant cardiovascular benefits.

Additionally, as briefly mentioned earlier, individuals with impaired thermoregulation due to medical conditions or advanced age may overheat more quickly and should therefore approach sauna use with appropriate caution.

Women who are pregnant or breastfeeding should avoid saunas entirely. Body temperatures above 38.3 °C (101 °F) can increase the risk of pregnancy complications and birth defects. Breastfeeding women face a higher risk of overheating from sauna use because their basal body temperature is naturally elevated during lactation.

Sauna use may not be safe for individuals prone to dehydration or who are already dehydrated. Sweating is the body's primary cooling mechanism in the sauna, and this can further worsen dehydration in these individuals. In extreme cases, dehydration can lead to kidney and brain damage, or even death. Therefore, sauna use should be avoided if dehydration is likely to be exacerbated.

Lastly, never use a sauna while under the influence of alcohol. The vast majority of serious injuries and deaths related to sauna use occur in individuals who were intoxicated. One study from Korea found that of 103 sauna deaths over seven years, 76 individuals had blood alcohol levels exceeding 0.08.

Outside of these specific situations, sauna use is generally safe and well-tolerated at recommended temperatures and durations, even for individuals who are not in perfect health.

Conclusion

So, does sauna bathing actually provide health benefits? The answer appears to be:

very likely yes—provided that the protocols mirror those used in the highest-quality studies reviewed above.

Considering the effect size, consistency, and biological plausibility of the evidence supporting sauna use, along with other Bradford Hill criteria (see Table 1), it is reasonable to conclude that sauna use is most likely causally linked to health benefits. This is especially true for cardiovascular health (still the leading global cause of death), where some of the most substantial and consistent positive effects were observed. Regardless of whether part of sauna’s apparent benefit stems from a healthy user effect, the fact remains that paying attention to one's health and actively supporting longevity is never a bad idea. The actual magnitude of effect is probably lower than what large-scale epidemiological studies suggest—not only because the healthy user effect can never be fully eliminated, but also due to numerous social benefits embedded in those studies.

There is, however, one more important caveat related to sauna use: opportunity cost. Setting aside financial costs, let's focus on something more valuable than money—time. If you’re spending 30 minutes a day in the sauna but claim you have no time for physical activity, it might be worth reassessing your priorities. There’s a clear hierarchy of lifestyle interventions we should follow when building healthy habits. At the core remain movement, sleep, and nutrition. Think of these as the foundation of your house. Make sure your house is in order before you step outside in search of extras like the sauna—even though it may add further value.

Personally, I have a dry sauna at home and try to use it at least three times per week. I typically do two sessions lasting 12–15 minutes at a temperature of 90–98 °C. I usually go in the evening before bed, together with my wife, and we both greatly enjoy this time together.

Sources:

• Peter Attia, https://peterattiamd.com/sauna-facts-myths-and-how-to/

• Rhonda Patrick, https://www.foundmyfitness.com/topics/sauna

• Nick Norwitz, How Heat Transforms Your Body, https://youtu.be/6OH4NlFqd58?si=ACMcsrmqW88CpU5P