Sauna and longevity

Men in a large Finnish study who used the sauna 4 to 7 times a week lived longer than men who went once a week. Their risk of dying from any cause during follow-up was 40% lower.^[1] The study, called KIHD, followed 2,315 middle-aged men for about 20 years.^[1] It was observational, meaning the researchers watched people instead of assigning them a sauna habit. So it shows a link, not that the sauna caused it.

The table shows how the death rate fell with each step up in frequency:

Source: KIHD, 2,315 Finnish men, median follow-up 20.7 years.^[1]

The third column is the raw share of men who died, while the last one compares death rates after adjusting for other risk factors.^[1] The same pattern held for deaths from heart disease, and fatal heart and blood vessel events were about half as common in the most frequent group.^[1] The link was stronger still for sudden cardiac death, when the heart stops without warning.^[1]

Sudden cardiac death was also linked to how long a session lasted.^[1] The average session in these classic Finnish dry saunas lasted about 14 minutes at about 79°C.^[1] Men who sat for more than 19 minutes had about half the sudden-death risk of men who stayed under 11 minutes.^[1] Their risk of dying from any cause, though, was no lower, and temperature did not track survival either.^[1] The most frequent bathers even sat in slightly cooler rooms than the once-a-week men.^[1] So for living longer, these data give no reason to chase hotter rooms or longer sessions.

How often men went, by contrast, stayed linked to survival decades later and to health beyond the heart. Almost three decades on, KIHD men who went 3 to 7 times a week still had a lower death rate than men who went twice or less.^[13] In another analysis of these men, the top group also had a 66% lower risk of dementia than once-a-week men.^[2] Both results come from the same Finnish study, so they share its limits.

Those limits are the ones of any study that watched instead of tested. Healthier men may simply have gone to the sauna more often, and education, income and lifestyle can never be fully adjusted away. The researchers did account for smoking, alcohol, blood pressure, diabetes and other risk factors, and the death link held.^[1] Sauna habits, though, were asked about only once, at the start.^[1] The top group also held just 201 men, which is a modest crowd for a number that travels this far.^[1]

All of these men were Finnish, too, and all large mortality data come from this one region of Finland. A later KIHD sample from the same region was about half women.^[9] For men and women together, 4 to 7 weekly sessions went with a much lower risk of dying from heart and blood vessel disease than one session.^[9] The researchers found no clear difference between the sexes, yet among women alone the link was not statistically clear.^[9] That leaves the Finnish figures strongest for middle-aged men, while for women they point the same way on thinner data.

A sauna session works your heart much like moderate exercise such as brisk walking, pushing heart rate to about 120 to 150 beats per minute.^[4] You also sweat heavily, and your blood vessels widen.^[4] Since you get this exercise-like response while sitting still, sauna can be useful for people who can't train hard because of a health issue.^[4]

Blood pressure is less predictable while you sit in the heat. In one lab study, systolic pressure (the top number on a blood pressure monitor) fell during 30 minutes at 73°C.^[12] In another, blood pressure rose during 25 minutes at 93°C and dropped below its starting level only after the session.^[27] That drop after the session is the more consistent finding. In a Finnish study of 102 adults, 30 minutes at 73°C left systolic pressure 7 mmHg (millimetres of mercury, the unit of blood pressure) lower right afterwards.^[3] Half an hour of rest later, it was still below where it started.^[3]

A drop that holds for half an hour is not yet a lasting change. Whether regular sauna changes your blood vessels over weeks is less clear. The review behind the heart-rate figure notes that most blood pressure studies were in people who already had vascular disease, or measured only the short-term effect.^[4] Some of the evidence on the blood vessels' inner lining also comes from infrared or hot-water therapy, not Finnish sauna.^[4]

Finnish sauna itself was then tested directly in a randomized trial, which assigns people to groups by chance. Its 41 participants had stable coronary disease, meaning narrowed heart arteries.^[14] About half of them used a 79°C sauna 4 times a week for 8 weeks, while the rest kept their usual lifestyle.^[14] Compared with that control group, the sauna group showed no improvement in blood pressure, artery flexibility or how well the blood vessels' inner lining worked.^[14]

A meta-analysis, which pools the results of earlier trials, points the same way. Across 20 randomized trials of passive heating, from saunas to hot baths, it found no clear effect on most heart and vessel markers.^[15] Systolic pressure fell by about 2.5 mmHg on average, but the uncertainty range included no effect.^[15] So the short-term response is well documented, while lasting changes to arteries and blood pressure remain unproven in trials.

Paired with exercise, sauna has one more encouraging trial. For 8 weeks, inactive adults with at least one heart risk factor either exercised, exercised and then sat 15 minutes in the sauna, or did neither.^[5] Compared with exercise alone, the sauna group improved more in fitness and blood pressure.^[5] Their systolic pressure fell by about 8 mmHg more, and total cholesterol dropped a little more too, though that extra drop was less certain.^[5]

The fitness gain needs a closer look. The trial measured fitness as VO2 max, the amount of oxygen your body can use during hard exercise.^[5] It estimated that value from a bike test below maximum effort rather than measuring it directly.^[5] The sauna group's larger gain also partly reflects a lower starting point, and by the end of the trial both exercise groups were equally fit.^[5]

What the trial does show is that a sauna after the workout did not blunt the training gains.^[5] Because the heat came on top of the workouts, the trial supports sauna as an addition to structured exercise rather than a replacement for it.

Heat shock proteins help other proteins keep their shape under stress, and your body makes more of them when it gets hot. They are a plausible part of the explanation for sauna's links with heart health and survival, but the evidence is thin. It rests on one short lab study in humans and on lifespan data from worms. In the human study, 13 young adults sat for one 30-minute session at 73°C.^[12] Their blood levels of HSP72, one of these proteins, rose by about half on average, with large differences between people.^[12]

That rise is a one-off reaction, and the link to a longer life comes from animal studies. In worms, boosting the master switch of the heat shock response extended lifespan.^[24] The idea behind it is hormesis, a small dose of stress that makes cells tougher. Whether regular sauna use builds a lasting protective response like this in humans has not been shown.

In the Finnish KIHD study, the lowest death rate was seen in men who used a traditional dry sauna 4 to 7 times a week.^[1] That was the most frequent group studied, not a tested prescription, and no trial has shown that going more often makes you live longer.

Fewer visits still counted: going 2 to 3 times a week was linked to a 24% lower death rate than once a week.^[1] The study had no group of non-users, so it can't say how sauna compares with none at all.^[1] Without a proven dose, a sensible start is a frequency that suits your health and schedule.

Once you have picked a frequency, the KIHD averages of about 14 minutes at about 79°C are a useful reference for each visit.^[1] A Finnish sauna usually runs at 80 to 100°C (176 to 212°F) with low humidity.^[4] Infrared cabins run cooler (a Japanese heart-failure study used 60°C).^[19] The big mortality studies, though, were done in traditional dry saunas, so their results don't simply carry over to infrared.^[1]

A common pattern in a Finnish sauna or a German or Austrian Therme (a large thermal spa) is 2 to 3 rounds, each with the same steps:

1. Sit in the heat for 10 to 15 minutes, and leave earlier if you feel dizzy.
2. Cool down with a lukewarm or cool shower. A cold plunge pool (Tauchbecken) is an alternative if you are healthy and used to it. With heart disease, high blood pressure or heart rhythm problems, skip the plunge unless your doctor has cleared it.^[4]
3. Rest for 5 to 10 minutes wrapped in a towel before the next round.
4. Drink water between rounds rather than during one, enough to replace what you sweat out, for example a glass or two between rounds and afterwards. If your doctor has set you a fluid limit (for example for heart failure or kidney disease), stick to it.

After training

In an 8-week trial of inactive adults, a sauna after exercise did not blunt fitness gains.^[5] Next-day performance is a different matter. In a study of competitive swimmers, three 8-minute rounds at 80 to 85°C after hard training made their swim times worse the next morning than rest did.^[18] If you race or train hard the next day, skipping the sauna after the session is the safer choice.

Before bed

There are no good sleep studies on sauna itself, only on warm baths and showers. Taken at 40 to 42.5°C 1 to 2 hours before bed, they helped people fall asleep faster and rate their sleep better.^[25] The likely reason is that core temperature drops afterwards.^[25] An evening sauna that ends an hour or two before bed may work the same way, but no study has shown that yet.

What this looks like in Germany, Austria and Switzerland

How often you can realistically go depends mostly on where your sauna is and what it costs. Munich's city pool saunas (SWM) have three ticket types (as of October 2026).^[26]:

• 4 hours: €23.
• Evening rate from 19:45: €17.50. At Müller'sches Volksbad, it starts 3 hours 15 minutes before closing instead.
• Day ticket: €34.50.

Large thermal spas and private sauna parks such as Therme Erding, Vabali or Therme Wien cost a multiple of that. Some use dynamic pricing, so check the operator's current price list. Mapped onto KIHD's frequency groups, those prices leave three realistic patterns:

• Twice a week: two visits to a pool sauna or a Therme put you in KIHD's 2-to-3-times group^[1] As an example calculation at SWM prices, that means 8 to 9 visits a month at €17.50 to €34.50, or about €140 to €310 a month.^[26]
• One spa visit plus one home session a week keeps you in the same 2-to-3-times range.^[1]
• 4 to 7 times a week, the KIHD top group, is realistic for most people only with a sauna at home.^[1] A badly fitted home sauna is a fire and ventilation risk, so have it installed by a trained sauna builder (Saunabauer).

Aufguss etiquette in a German or Austrian Therme

An Aufguss is the ritual where water is poured on the hot stones and the heat is fanned around the room. German and Austrian saunas have firm conventions around it. Sit on a towel so that no skin touches the wood. The sauna area is nude and kept separate from the swimwear (textile) area, so swimsuits stay outside. Get in before the Aufguss starts, because the door usually stays shut once it begins, and leave at any time if you feel unwell.

Most healthy adults and children tolerate a sauna well, and deaths in it are rare: fewer than 2 per 100,000 people a year in Finland.^[7][10] Children and older adults should still keep sessions shorter and the temperature lower. The real risks cluster in a few situations, namely unstable heart disease, fever, alcohol, some medicines, pregnancy and cold water straight after the heat. The warning signs below apply to everyone.

Warning signs and emergencies

If you feel dizzy or sick, leave the sauna, sit or lie down somewhere cool and cool down gradually. Chest pain or chest pressure is different, and so is a racing, irregular heartbeat that doesn't settle within minutes. For any of these, call the emergency number (112) right away and don't wait to see if it passes.^[22] If someone becomes confused, slurs their speech, collapses or has a seizure, that may be heatstroke.^[23] Call 112, stay with them and cool them quickly with cool water and wet cloths until help arrives.^[23]

Stay out of the sauna

These conditions make a session too risky until they are treated or have settled.^[4][10]:

• Unstable angina (chest pain that is new, getting worse or comes on at rest).
• A recent heart attack.
• Severe aortic stenosis (a badly narrowed heart valve).
• Uncontrolled high blood pressure.
• Heart failure that is getting worse or not well controlled.
• A fever or an acute infection or inflammation. Come back once you have recovered^[4]

People with stable coronary heart disease or an old heart attack usually tolerate sauna well.^[10] When to return after a heart attack, though, is a decision for your cardiologist.

Ask your doctor first

• Other heart or valve disease.^[4]
• Low blood pressure or dizziness when you stand up, since blood pressure can drop sharply during or after a session.^[4]
• Skin conditions that flare with heat, such as hives (urticaria), or open skin.^[4]
• Pregnancy, trying to conceive and regular medication, each covered below.

Pregnancy

The worry in pregnancy is the mother's core temperature reaching 39°C or more early on, when the neural tube (which becomes the brain and spinal cord) forms.^[17] Pooled studies link high body heat in early pregnancy, mostly from fever, to about twice the odds of neural tube defects.^[8] For sauna itself the picture is calmer, since an older review judged it safe in uncomplicated pregnancies of healthy women.^[10] In a 2019 review, only one small study measured core temperature in pregnant women in a sauna, and the women were used to sauna bathing. They sat in a dry sauna at 70°C and about 15% humidity for up to 20 minutes and stayed below 38°C, well short of 39°C.^[17] The review rated this evidence as weak, and it covers dry heat only, not steam rooms or a humid Aufguss at 90°C.

So if you use the sauna while pregnant, stay close to those tested conditions by keeping it cooler, drier and shorter than usual.^[17] Leave as soon as you feel hot or unwell, and agree it with your gynecologist. If in doubt, skip it during the first trimester.

Trying to conceive

Regular sauna use can lower sperm count for a while, which matters if you are trying for a baby. In a small study, 10 healthy men used a Finnish sauna (80 to 90°C) twice a week for 15 minutes over 3 months.^[16] Their sperm count and motility (how well sperm swim) dropped clearly, and both had fully recovered 6 months after the men stopped.^[16] If you are trying to conceive, consider pausing regular sauna use and talk to your doctor.

Medicines

These medicines can make heat harder to handle, so look for yours in the first column.^[21]:

Source: US guidance on heat and medicines, not sauna-specific studies^[21]

If you take any of these regularly, ask your doctor or pharmacist before regular sauna use, and don't change a dose on your own.

Insulin needs its own plan. In a small study of people with type 1 diabetes, two 25-minute sessions at 85°C more than doubled how fast injected fast-acting insulin was absorbed.^[11] Their blood sugar ended up 3.0 to 3.3 mmol/L (millimoles per litre) lower than on a normal day.^[11] A second study by the same author narrows that finding: with a slower-acting insulin, heat had no clear effect.^[20] Modern insulins and pumps were not studied. If you use insulin, check your blood sugar before and after, keep a snack at hand, and agree any dose change with your diabetes team.^[11]

Alcohol

In a Finnish forensic study of sauna deaths, half of those who died had been drinking.^[7] The authors' prevention advice centred on exactly that: drink less, and never leave a drunk person alone in the sauna.^[7] A 2001 review adds that alcohol during a sauna raises the risk of low blood pressure, heart rhythm problems and sudden death.^[10] So skip alcohol on sauna days, or keep it small and after the session.

Cold plunge after the heat

A plunge into ice-cold water after the heat, the sauna version of cold exposure, sharply raises blood pressure and strains the heart.^[4] Deaths have been reported in people who dived head first into cold water straight after a sauna.^[4] If you have heart disease, high blood pressure or heart rhythm problems, cool down with a lukewarm shower instead. Skip the cold plunge unless your doctor has cleared it.^[4]