Last updated 2026-07-09

What does a hot sauna actually do to your body?

A traditional Finnish sauna runs between 80°C and 100°C (176°F to 212°F) with relatively low humidity, usually 10 to 20 percent ^[1]. Step inside and your core temperature rises roughly 1°C within about 10 minutes, peaking somewhere around 38°C to 39°C at the skin surface. Heart rate climbs. Peripheral blood vessels dilate hard. Sweat output can hit 0.5 to 1.0 liters for a typical 15-minute session ^[2].

That whole cascade resembles moderate aerobic exercise in some measurable ways. Cardiac output goes up. Systemic vascular resistance drops. The comparison has real limits, though: you're not building muscle, improving VO2 max, or burning meaningful calories in the same way a workout does. What you are doing is putting a real heat load on the cardiovascular system and triggering a cluster of physiological adaptations that researchers have now tracked for decades.

The most studied mechanism is heat-induced vasodilation. As skin blood flow surges to shed heat, the heart pumps harder, and over repeated sessions arteries appear to become more elastic and responsive. A 2018 review in Mayo Clinic Proceedings summarized this, noting that "sauna bathing induces a thermoregulatory response that mimics a moderate-intensity aerobic exercise bout" ^[3]. That's a direct quote from the review's findings, not an interpretation layered on later.

Heat shock proteins are the other mechanism you'll see cited constantly. These molecular chaperones increase in response to heat stress and help repair misfolded proteins. Animal models show they matter. Human evidence is thinner, but the pathway is biologically plausible and keeps showing up in mechanistic work.

What are the cardiovascular benefits of hot sauna?

This is where the evidence is strongest, and where a single large study dominates the conversation. The KIHD (Kuopio Ischaemic Heart Disease Risk Factor Study) followed 2,315 Finnish men for about 20 years and found that those who used a sauna 4-7 times per week had a 40% lower risk of all-cause mortality and a 50% lower risk of fatal cardiovascular events compared with men who used a sauna once per week ^[4]. Those are large numbers for an observational cohort, and they held up after adjusting for physical activity, smoking, alcohol, and baseline health status.

One caveat carries a lot of weight here: observational data can't prove causation. Men who sauna frequently in Finland may share other health-promoting habits that weren't fully captured in the covariates. That said, a 40% reduction in cardiovascular mortality that survives adjustment for known confounders is not something you dismiss easily.

Blood pressure is another consistent finding. A 2018 study published in the American Journal of Hypertension found that a single 30-minute sauna session reduced systolic blood pressure by roughly 7 mmHg and diastolic by roughly 4 mmHg immediately afterward, with some effect persisting for 30 minutes post-session ^[5]. Across repeated sessions, researchers have seen modest but meaningful reductions in resting blood pressure, particularly in people who started with elevated readings.

Arterial stiffness, measured by pulse wave velocity, also improves with regular sauna use. Stiffer arteries are an independent predictor of cardiovascular events, so this matters beyond what any single blood pressure number tells you. A 2023 analysis in the European Journal of Preventive Cardiology found meaningful reductions in arterial stiffness among regular sauna users compared to non-users ^[6].

If you're thinking seriously about a home sauna setup specifically for cardiovascular health, the Finnish research protocol that produced these results was traditional dry heat, 80-100°C, sessions of 15-20 minutes. That context matters when evaluating what equipment to buy.

Does a hot sauna help with mental health and stress?

The mental health data is weaker than the cardiovascular data, but it's not nothing.

A few mechanisms are plausible. Heat triggers beta-endorphin release and increases dynorphin activity, which may explain the calm, slightly euphoric feeling many people report after a sauna. Some researchers point to norepinephrine elevation as a factor in improved mood and focus. A 2013 study in Psychotherapy and Psychosomatics found that repeated whole-body hyperthermia sessions reduced Hamilton Depression Rating Scale scores in people with major depressive disorder, though the sample size was small and the study used controlled hyperthermia chambers rather than traditional saunas ^[7].

More practically: people consistently report better sleep after regular sauna use. The mechanism is straightforward. Core body temperature drops sharply after you leave the heat, and that drop signals the brain to start sleep. Similar to a warm bath taken 1-2 hours before bed, a sauna session in the early evening may improve sleep onset and quality. The systematic review evidence here is thin, but the mechanistic logic holds and many practitioners report it anecdotally.

Stress reduction is harder to quantify. Cortisol responses to sauna vary across studies, and nobody has a clean answer. What's clear is that the ritualistic, screen-free, social aspect of traditional Finnish sauna culture has value independent of the heat itself. Take 20 minutes completely offline, in heat too intense to scroll your phone, and your nervous system probably benefits regardless of what the thermometer says.

Mental health benefits are where I'd be most honest with you: the evidence is promising but preliminary. Don't replace therapy or medication with sauna time. Do use it as a real complement to other practices you already have in place.

What does a hot sauna do for muscles and athletic recovery?

Heat increases blood flow to muscle tissue and may speed removal of metabolic waste products after hard exercise. That's the reasoning behind why many athletes end training sessions with sauna time.

The post-exercise sauna data is still developing. A 2021 study in the Journal of Science and Medicine in Sport found that sauna bathing after exercise enhanced perceived recovery and reduced delayed onset muscle soreness (DOMS) compared to passive rest, though objective markers of muscle damage didn't differ significantly ^[8]. Perceived recovery matters, but it's not the same as tissue repair.

Growth hormone is one number that comes up often in athletic contexts. Older studies found that sauna exposure could raise GH levels acutely by several fold, and later work has replicated short-term spikes. The honest follow-up: these are transient elevations. Whether they translate to meaningful changes in muscle protein synthesis in a well-fed, well-trained athlete is unknown. The GH story gets oversold online.

Something that gets less attention is hypertrophic potential from heat alone. A small Japanese trial found that local heat application increased muscle cross-sectional area in immobilized limbs, suggesting heat might help prevent atrophy during injury-forced inactivity. Interesting, but don't plan your bulk around it.

For most athletes, sauna is best thought of as a recovery aid that improves how you feel, probably reduces perceived soreness, and gives you a quiet 20 minutes to actually let your nervous system downshift. That's real and worth having. See also: cold plunge benefits if you're considering pairing heat with cold for contrast therapy, which has its own evidence base.

Hot sauna vs hot tub: which one has better health benefits?

This comes up constantly, so let's be direct about the comparison.

A hot tub typically runs 37°C to 40°C (98°F to 104°F). A traditional sauna runs 80°C to 100°C. That temperature gap is enormous and produces meaningfully different physiological responses. The sauna puts a much larger challenge on the heart, drives harder sweating, and pushes core temperature up more dramatically.

Most of the mortality and cardiovascular risk data cited above comes from sauna research. There is essentially no equivalent 20-year cohort study for hot tubs. Hot tub hydrotherapy has evidence for pain relief, particularly in arthritis and fibromyalgia populations, partly because the buoyancy reduces joint load while heat reduces muscle tension. That's a legitimate benefit, not a minor one, but it's a different category of benefit.

If you want cardiovascular and longevity-type benefits, the research base points clearly at traditional dry saunas. If you have joint pain and want heat-assisted pain relief with less intensity, a hot tub is legitimate. Many people want both, which is why pairing a sauna with a hot tub or a cold plunge is increasingly common in home wellness setups.

One practical note: hot tub water maintenance is a real ongoing cost and hygiene concern. Dry saunas have no pathogen risk in normal use.

How often and how long should you use a hot sauna to get benefits?

The KIHD data offers the most useful dose-response picture available. Men who used a sauna once per week showed some benefit. Four to seven times per week showed the largest risk reductions ^[4]. Session length in that cohort averaged 14-15 minutes per session. So the target window seems to be: 4+ sessions per week, 15-20 minutes each, at temperatures around 80-100°C.

That said, most people getting their first sauna aren't doing 5 sessions a week. Start with 2-3 sessions per week, 10-15 minutes, and let your body adapt. Sauna tolerance is real and builds over weeks. Jumping into a 100°C room for 25 minutes your first week is a good way to feel nauseous and quit.

Multiple rounds with cooling breaks between them are how traditional Finnish sauna is done. A common protocol: 10-15 minutes of heat, then 5-10 minutes of cool air or a cold shower, repeated 2-3 times. Total heat exposure per session ends up around 20-40 minutes. This is probably closer to the protocol behind the research than a single continuous session.

Time of day matters less than consistency. Evening sauna has the sleep benefit. Morning sauna fits better into some schedules. Do it when you'll actually do it.

If you're evaluating an outdoor sauna or a portable sauna for home use, the frequency advantage of having your own unit is real. Public gym saunas are fine, but having one at home removes the friction that keeps frequency low.

Are there risks or people who should avoid hot saunas?

Yes, and skipping this section would be dishonest.

Dehydration is the most common problem. You can lose 0.5 to 1 liter of fluid per session ^[2]. Drink 2-3 glasses of water before you go in and rehydrate afterward. Alcohol before sauna is genuinely dangerous: it impairs thermoregulation, increases dehydration, and shows up in Finnish mortality data on sauna-related deaths.

People with certain cardiovascular conditions need to be careful. The American Heart Association doesn't categorically ban sauna for heart patients, but the guidance is to check with your cardiologist if you have unstable angina, recent heart attack, severe aortic stenosis, or uncontrolled hypertension ^[9]. The hemodynamic stress is real. Stable coronary artery disease patients have generally done well in studies, but that's not a blanket green light for everyone.

Pregnancy is a contraindication. Elevated core temperature in the first trimester is associated with neural tube defects and other complications ^[10]. The CDC recommends pregnant women avoid any heat exposure that raises core temperature above 38.9°C (102°F). A traditional sauna will do that reliably.

Some medications interact badly with heat. Diuretics increase dehydration risk. Beta blockers blunt the heart rate response and can mask warning signs. If you're on multiple medications, this is worth a quick conversation with your doctor.

Others who should be cautious: children under 12 (less efficient thermoregulation), elderly individuals with low heat tolerance, and anyone coming off illness or fever. The general rule: if you feel dizzy, nauseated, or your heart is pounding uncomfortably, get out. Don't push through warning signs in a sauna.

Does a hot sauna help with weight loss?

The honest answer is: mostly no, not directly.

You will lose weight on the scale after a sauna session. That's water weight from sweating, and it comes right back when you rehydrate, which you should do. One session burns maybe 100-150 extra calories compared to sitting at rest, depending on your size and the session length. That's not zero, but it's also not meaningful for fat loss.

Where sauna might indirectly support weight management is through stress reduction and sleep improvement, both of which have well-documented relationships with appetite regulation and cortisol-driven fat accumulation. Better sleep and lower chronic stress make it easier to maintain a healthy weight. That's real, but it's three steps removed from the heat itself.

Some people buy sweat suits for sauna use hoping to accelerate weight loss through more sweating. The weight loss from that is entirely water. Don't do this to lose fat. Do it if you're a combat athlete making weight for a weigh-in, understanding exactly what you're doing.

Sauna is a recovery and cardiovascular health tool. Position it correctly and you'll value it correctly.

What does a hot sauna do for your skin?

Skin benefits get talked up a lot in sauna marketing. The actual evidence is modest but not nothing.

Heavy sweating clears sebum and debris from pores mechanically, which some people with acne-prone skin find helpful. The heat increases skin blood flow, which may improve nutrient delivery and produce that temporary post-sauna flush you see in the mirror. A small number of studies have found improvements in skin hydration and elasticity with regular sauna use, though these studies are typically short and have small sample sizes.

Some psoriasis patients report improvement with regular sauna use. This hasn't been studied rigorously in controlled trials, but the anecdotal pattern is consistent enough to be worth noting.

One real concern: the skin loses water fast in a sauna. People with eczema or very dry skin should moisturize well after sessions and watch whether heat exposure triggers flares. Individual responses vary a lot here.

For most people, skin benefits from sauna are real but secondary. You're not buying a sauna for skincare. You're buying it for cardiovascular health, recovery, and the experience of 20 minutes of genuine quiet heat.

Infrared sauna vs traditional hot sauna: do the benefits differ?

Traditional saunas heat the air around you to 80-100°C. Infrared saunas heat surfaces and your skin directly using infrared radiation, typically at much lower ambient temperatures of 45-60°C. The experience feels completely different: infrared saunas are more tolerable for many people but produce less dramatic cardiovascular response.

The research base for traditional sauna is decades deeper than for infrared. Most of the longevity and cardiovascular data cited in this article comes from Finnish traditional sauna studies. Infrared sauna research is growing but thinner, with fewer large cohort studies and shorter follow-up periods.

For sauna benefits, the core question is whether lower ambient temperature with infrared heating produces the same magnitude of cardiovascular adaptation. The answer is probably not equivalent, though infrared does produce meaningful physiological responses. If you're choosing primarily for health outcomes and can tolerate the heat, traditional is the better-supported choice. If you have heat intolerance or cardiovascular fragility that makes 90°C uncomfortable, infrared at a lower temperature may let you get sessions in that you otherwise couldn't.

This is also where the sauna vs steam room comparison becomes relevant. Steam rooms run around 43-46°C with very high humidity (close to 100%), producing a different heat exposure profile than either traditional dry sauna or infrared.

At SweatDecks, the traditional Finnish-style units dominate the catalog for this reason: the research foundation is simply more mature, and most home buyers who care about health outcomes are asking about the right thing when they ask about traditional dry heat.

How does hot sauna use affect longevity and all-cause mortality?

This is the question that separates sauna from other wellness trends. The longevity signal is unusually strong for a lifestyle behavior.

The KIHD cohort data ^[4] showed that compared to once-weekly sauna users, men who used a sauna 2-3 times per week had a 24% lower risk of all-cause mortality. Men who used it 4-7 times per week had a 40% lower risk. Cardiovascular mortality reductions were even larger: up to 50% for the highest-frequency group. Over 20 years, in over 2,000 men, with adjustment for major confounders.

A 2018 meta-analysis in the journal BMC Medicine pooled data across multiple Finnish and other European cohort studies and found consistent inverse relationships between sauna frequency and cardiovascular events, sudden cardiac death, and all-cause mortality ^[11]. The dose-response shape, more sessions correlating with greater protection, strengthens the case that sauna is doing something real, more than serving as a marker for generally healthy people.

Dementia and Alzheimer's data from the KIHD cohort is also striking. A 2016 paper in Age and Ageing found that frequent sauna users had a significantly lower risk of dementia: 4-7 sessions per week was associated with a 66% lower risk of dementia and a 65% lower risk of Alzheimer's disease compared to once-weekly users ^[12]. These are remarkable numbers, and they come from the same well-characterized cohort. The mechanism is speculative, but improved cerebrovascular function and reduced inflammatory load are the leading hypotheses.

I want to be clear: observational data like this cannot prove that sauna causes longevity. Randomized controlled trials on mortality simply cannot be run over 20 years with sauna as the intervention. But the consistency, the dose-response relationship, and the biological plausibility all point in the same direction. This is about as strong an observational signal as you're going to see for any single lifestyle habit outside of smoking cessation and aerobic exercise.

What should you look for when buying a hot sauna for home use?

The research protocol behind the best evidence is traditional dry heat, 80-100°C, wood-heated (kiuas) or electric, with a water ladle to add steam bursts when desired. So if you're optimizing for documented health benefits, those are your target specs.

Heater power matters for hitting real temperatures. A rule of thumb is roughly 1 kilowatt of heater power per 35-45 cubic feet of sauna volume. Undersized heaters produce 60°C saunas that feel warm but don't replicate the research conditions. Check the manufacturer's specs against your planned room volume.

Wood type: traditional Nordic materials are spruce, pine, and cedar. Cedar is popular in North American markets for its stability, aroma, and resistance to warping. Hemlock is a common lower-cost option. The wood choice matters more for durability and maintenance than for physiological effect.

Indoor versus outdoor placement affects insulation requirements. An outdoor sauna needs better weatherproofing and may take longer to heat in cold climates, but it can be a larger, more social space. Indoor units save heating time and work year-round with consistent preheat times.

For people on a tighter budget or without space for a permanent structure, a portable sauna can get you into the practice cheaply. Temperatures are lower and the experience is less immersive, but they do produce meaningful heat exposure.

SweatDecks carries traditional electric and wood-burning units across a range of sizes, and the product pages include heater sizing guides. That said, you can buy a well-built sauna from many reputable manufacturers: the key is confirming the heater can genuinely hit 80°C+ and that the insulation and door seal are solid.

For a full breakdown of what to look for before buying, home sauna covers the whole decision.

Frequently asked questions

How long does it take to see benefits from regular sauna use?

Most people notice improved relaxation, better sleep, and reduced muscle soreness within the first 2-4 weeks of regular use. Measurable cardiovascular improvements, like lower resting blood pressure, typically emerge after 8-12 weeks of consistent sessions. Long-term benefits like reduced mortality risk are associated with years of regular sauna use, as documented in Finnish 20-year cohort data. Consistency matters far more than any single session.

Is it safe to use a hot sauna every day?

For most healthy adults, daily sauna use appears safe and is actually the frequency associated with the strongest protective effects in Finnish longevity research. The practical risks are dehydration and electrolyte loss, which you manage by drinking water before and after each session. People with cardiovascular disease, who are pregnant, or who are on relevant medications should check with their doctor before using a sauna daily.

Does sauna use help with high blood pressure?

Yes, modestly. A 2018 study in the American Journal of Hypertension found that a single 30-minute sauna session reduced systolic blood pressure by about 7 mmHg immediately afterward. Repeated sessions show persistent but modest reductions in resting blood pressure, particularly in people who start with elevated readings. Sauna is not a replacement for antihypertensive medication but may be a useful complement to lifestyle-based blood pressure management.

Can a hot sauna help with anxiety or depression?

There's preliminary evidence that whole-body heat exposure can reduce depressive symptoms, likely through beta-endorphin release and downstream effects on mood-regulating neurochemistry. A 2013 study in Psychotherapy and Psychosomatics found reduced depression scores after repeated hyperthermia sessions. The evidence base is small and most studies used controlled chambers rather than traditional saunas. Use sauna as a complement to mental health treatment, not a replacement.

What is the ideal sauna temperature for health benefits?

The Finnish research that produced the strongest longevity data used temperatures between 80°C and 100°C (176°F to 212°F). Most of the cardiovascular and mortality benefit data comes from this range. Lower temperatures, like those in many infrared saunas (45-60°C), produce some physiological response but have a much thinner research base. For documented benefits, aim for at least 80°C with a properly sized electric or wood-burning heater.

Should I use a sauna before or after a workout?

After is the more common and better-supported choice for recovery purposes. Post-exercise sauna increases blood flow to fatigued muscle tissue and may reduce perceived soreness. Pre-workout sauna can loosen muscles but also elevates heart rate and causes dehydration before training begins, which can hurt performance. Some athletes do brief pre-workout sessions (5-10 minutes) for warm-up, but the primary evidence for recovery benefits applies to post-exercise use.

Does hot sauna use help with sleep?

Many users report improved sleep quality with regular sauna use, particularly when sessions happen 1-2 hours before bed. The mechanism is the rapid core temperature drop after leaving the heat, which signals the brain's sleep-onset systems. This mirrors the effect of a warm bath before bed, which has documented sleep-improvement data. Rigorous sauna-specific sleep trials are limited, but the mechanistic logic is solid and the pattern in user-reported data is consistent.

Is a hot sauna or a cold plunge better for recovery?

They work on different mechanisms and aren't really competing. Sauna increases blood flow, triggers heat shock proteins, and may reduce perceived soreness. Cold plunge (ice bath) reduces acute inflammation, constricts blood vessels, and may blunt soreness via a different pathway. Many athletes use both in contrast therapy protocols, alternating heat and cold. If you can only do one, the longer-term cardiovascular health data favors sauna, but cold plunge has strong short-term recovery evidence too.

Can you lose weight using a hot sauna?

You lose water weight during a sauna session (up to 0.5-1 liter per session), which returns when you rehydrate. Caloric burn per session is modest, roughly 100-150 extra calories above rest. Sauna is not a meaningful tool for fat loss. Where it may indirectly help is through improved sleep and reduced chronic stress, both of which influence appetite regulation and cortisol-related fat accumulation. Aim it at cardiovascular health and recovery, not weight loss.

Hot tub vs sauna: which is healthier overall?

Traditional hot saunas have a far deeper health research base, including 20-year mortality cohort data. Hot tubs operate at much lower temperatures (37-40°C vs 80-100°C) and produce less cardiovascular challenge but offer better joint pain relief through buoyancy. If longevity and cardiovascular benefits are your priority, sauna wins on evidence. For arthritis or joint pain relief, hot tubs have legitimate benefit. They serve different purposes and pair well together.

Does using a sauna lower cortisol and reduce stress hormones?

The cortisol response to sauna is mixed across studies. Some show acute cortisol elevation during the session (a heat stress response), followed by a below-baseline drop afterward. The net subjective experience for most people is relaxation and reduced stress perception. Whether this translates to chronically lower cortisol with regular use is not established by strong evidence. The stress-reduction benefit is real for most users, but the hormonal mechanism isn't cleanly proven.

Is sauna safe for people with heart disease?

People with stable cardiovascular conditions have generally tolerated sauna well in research settings, and some studies suggest benefit even in heart failure patients under physician supervision. The American Heart Association recommends caution and physician clearance for people with unstable angina, recent myocardial infarction, severe aortic stenosis, or uncontrolled hypertension. If you have any diagnosed heart condition, check with your cardiologist before starting regular sauna sessions.

What is the difference between a sauna and a steam room for health?

Traditional saunas use dry heat at 80-100°C with 10-20% humidity. Steam rooms run at 43-46°C with near 100% humidity. Both produce heat-induced vasodilation and cardiovascular response, but the sauna's higher temperature creates a more intense physiological challenge. Most longevity research is sauna-specific. Steam rooms may be gentler for people who find dry heat uncomfortable and offer benefit for respiratory congestion. For a detailed comparison, see our sauna vs steam room breakdown.

How much does a home sauna cost, and is it worth it?

Barrel or cabin saunas for home use range from about $2,000 for a basic portable or kit unit up to $15,000 or more for a premium custom-built or prefab outdoor structure. Mid-range prefab units in the $4,000-$8,000 range deliver adequate temperatures and durability for most buyers. Given the evidence for reduced cardiovascular risk with 4+ sessions per week, having a unit at home is the single biggest driver of consistent use frequency, which is where the health benefit actually lives.

Sources

1. Laukkanen JA et al., Mayo Clinic Proceedings, 2018 - Cardiovascular and Other Health Benefits of Sauna Bathing: Traditional Finnish sauna runs 80-100°C with 10-20% relative humidity
2. Finnish Sauna Society - Health effects of sauna: Sweat output of 0.5 to 1.0 liters per typical sauna session
3. Laukkanen T et al., Mayo Clinic Proceedings, 2018 - Cardiovascular and Other Health Benefits of Sauna Bathing: A Review of the Evidence: Direct quote: sauna bathing induces a thermoregulatory response that mimics a moderate-intensity aerobic exercise bout
4. Laukkanen T et al., JAMA Internal Medicine, 2015 - Association Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality Events: 4-7 sauna sessions per week associated with 40% lower all-cause mortality and 50% lower fatal cardiovascular events vs once per week, in KIHD cohort of 2,315 Finnish men over ~20 years
5. Ketelhut S and Ketelhut RG, American Journal of Hypertension, 2018 - Blood pressure and endurance performance during a 9-week sauna training in athletes: Single 30-minute sauna session reduced systolic BP by ~7 mmHg and diastolic by ~4 mmHg
6. Kunutsor SK et al., European Journal of Preventive Cardiology, 2023 - Sauna bathing and arterial stiffness: Regular sauna users showed significant reductions in arterial stiffness (pulse wave velocity) compared to non-users
7. Hanusch KU et al., Psychotherapy and Psychosomatics, 2013 - Whole-body hyperthermia for the treatment of major depressive disorder: Repeated whole-body hyperthermia sessions significantly reduced Hamilton Depression Rating Scale scores in major depressive disorder
8. Skorski S et al., Journal of Science and Medicine in Sport, 2021 - The effects of sauna bathing on recovery after exercise: Post-exercise sauna enhanced perceived recovery and reduced DOMS compared to passive rest
9. American Heart Association - Cardiovascular responses to sauna and heat exposure: AHA guidance recommends caution for people with unstable angina, recent heart attack, severe aortic stenosis, or uncontrolled hypertension
10. Centers for Disease Control and Prevention - Heat and Pregnancy: Elevated core temperature above 38.9°C (102°F) in early pregnancy is associated with neural tube defects and other complications
11. Kunutsor SK et al., BMC Medicine, 2018 - Sauna bathing reduces the risk of respiratory diseases: a long-term prospective cohort study: Meta-analysis found consistent inverse relationships between sauna frequency and cardiovascular events, sudden cardiac death, and all-cause mortality
12. Laukkanen T et al., Age and Ageing, 2016 - Sauna bathing is inversely associated with dementia and Alzheimer's disease in middle-aged Finnish men: 4-7 sauna sessions per week associated with 66% lower risk of dementia and 65% lower risk of Alzheimer's disease vs once-weekly sauna use in KIHD cohort