LONGEVITY

A sauna isn't just relaxation: 4 to 7 sessions a week were linked to 61% fewer strokes

El sauna no es solo relajación: 4 a 7 veces por semana se asociaron con 61% menos derrames cerebrales

Illustrative image. Does not represent guaranteed results.

What your body does when it steps into the heat

There's something your body does very well, without you asking: it defends its temperature. The moment you walk into a room at 80 to 90 °C (176 to 194 °F), a whole system switches on. Your skin fills with blood to release heat. Your sweat glands open. Your heart beats faster to move that blood toward the surface. And your blood vessels, which were tight, relax.

If that sounds like what happens when you walk briskly uphill, it's because it is similar. The heart rate during a sauna session overlaps with that of light to moderate exercise. The difference is that you aren't moving a single muscle.

That's the first thing worth understanding, because it changes the question. The question isn't "does a sauna relax you?" — you already know that, it's why you go. The question is whether the work your heart and blood vessels do in the heat leaves something behind when it's repeated many times over many years. And it turns out one country has been running exactly that experiment for decades without meaning to.

The study that put it on the map: 2,315 men, 21 years

In Finland the sauna isn't a gym luxury: it's part of the house. That gave researchers at the University of Eastern Finland something hard to find elsewhere: a large population where frequent sauna use is normal and infrequent use also exists, so the two can be compared.

The study is called the Kuopio Ischaemic Heart Disease Risk Factor Study, and almost everything you'll read here comes from it. Between 1984 and 1989, 2,315 men aged 42 to 60 were asked how many times a week they used the sauna and how long they stayed. Then they were followed. The median follow-up was 20.7 years.

Of those men, 601 went once a week, 1,513 went 2 or 3 times, and 201 went 4 to 7 times. By the end of follow-up there had been 190 sudden cardiac deaths, 281 deaths from coronary heart disease, 407 cardiovascular deaths and 929 deaths from any cause.

The raw numbers already point in one direction. Among those who went once a week, 10.1% died of sudden cardiac death. Among those who went 2 to 3 times, 7.8%. Among those who went 4 to 7 times, 5.0%. The same step pattern appears for coronary death (14.9% · 11.5% · 8.5%), cardiovascular death (22.3% · 16.4% · 12.0%) and death from any cause (49.1% · 37.8% · 30.8%).

That 63% comes from an analysis already adjusted for the usual cardiovascular risk factors: age, blood pressure, cholesterol, smoking, diabetes, weight. And the trend across the three groups was statistically significant.

Frequency and duration: what the evidence rewarded

Here's the detail most people skip, and it's the most useful one if you want to know what to do with this information.

The 2-to-3-times-a-week group also did better than the once-a-week group — a hazard ratio of 0.78 for sudden cardiac death — but that result was not statistically significant: the interval ran from 0.57 to 1.07, so it crossed 1. The clear result was in the 4-to-7-times group. Put simply: in this population, what was linked to the big difference was going almost every day, not going twice.

There was a second finding, independent of frequency: how long you stay in. Compared with men whose sessions lasted less than 11 minutes, those who stayed more than 19 minutes had a hazard ratio of 0.48 for sudden cardiac death — 52% less — with a significant trend. Sessions of 11 to 19 minutes landed in between, with no clear difference.

One important caveat: for death from any cause, duration showed no significant association, although it did for coronary and cardiovascular deaths. Not every outcome moves the same way, and that's worth saying.

Stroke, and the only study with women

Almost all of the sauna evidence comes from men. There's one exception, and it matters.

In 2018, in the journal Neurology, the same group published an analysis of stroke in 1,628 men and women aged 53 to 74 (mean age 62.7), none with a previous stroke. Over a median of 14.9 years, 155 strokes were recorded.

What gives this result weight is that it held up under adjustment. When the authors accounted for established cardiovascular risk factors, the association held. When they also accounted for physical activity and socioeconomic status — the two obvious suspects behind "people who use the sauna are people who take better care of themselves" — it held too.

And the association didn't change by age or sex: it was similar in men and women. It was similar for ischemic stroke and more modest for hemorrhagic stroke, which the authors attribute to there being only 34 cases of that type — too few to conclude anything.

Memory

In the same cohort of 2,315 men, with the same median follow-up of 20.7 years, there were 204 cases of dementia and 123 of Alzheimer's disease.

Compared with men who went once a week, those who went 4 to 7 times had a hazard ratio of 0.34 for dementia (0.16–0.71) and 0.35 for Alzheimer's (0.14–0.90). That's 66% and 65% less. The adjustment included age, alcohol, weight, systolic blood pressure, smoking, type 2 diabetes, previous heart attack, resting heart rate and LDL cholesterol.

And again the same dose pattern: the 2-to-3-times group came in at 0.78 for dementia and 0.80 for Alzheimer's, neither significant.

It's important to be honest about what this can and can't mean. A memory disease takes decades to develop, and a man who was already using the sauna rarely at 50 may have been going rarely because of something — fatigue, a heart that couldn't handle it, the silent start of something — and not the other way around. The authors say so plainly: more studies are needed to establish the mechanism.

Blood pressure — and its honest limit

This is one of the most interesting results, because it offers a possible explanation for everything above.

Researchers took 1,621 men aged 42 to 60 who did not have high blood pressure at the start and followed them for a median of 24.7 years. There were 251 new cases of hypertension (15.5%). Compared with men who had one session a week, those with 4 to 7 sessions had a hazard ratio of 0.54 (0.32–0.91) — 46% less — and the result held at 0.53 (0.28–0.98) after adjusting for glucose, creatinine, alcohol, heart rate, family history of hypertension, socioeconomic status and fitness.

If frequent sauna use is linked to developing less high blood pressure, that fits: high blood pressure is one of the drivers of heart disease, stroke and damage to the brain's blood vessels. It would be one path by which the rest makes sense.

But here's the limit, and it needs to be said clearly because it's exactly what someone with high blood pressure would want to know.

A later analysis of 2,575 men, with 744 cardiovascular deaths over a median of 27.8 years, crossed the two: systolic pressure and sauna frequency. Among men with high systolic pressure (140 or higher) who rarely used the sauna, the risk of cardiovascular death was 1.81 times that of men with normal pressure who used it often. And among men with high blood pressure who used the sauna often, the risk stayed elevated: 1.52 (1.06–2.16).

Put plainly: frequent sauna use does not cancel out high blood pressure. When the cutoff was set at 130 instead of 140, the excess risk among frequent sauna users was no longer significant (1.11; 0.77–1.61), which suggests the sauna may offset borderline-high pressure, but not established hypertension. If you have high blood pressure, the sauna isn't the treatment. The treatment is the treatment.

The lungs

In 1,935 men aged 42 to 61 followed for a median of 25.6 years, there were 379 hospital diagnoses of respiratory disease — COPD, asthma and pneumonia were counted. Compared with men who had one session a week or fewer, those with 2 to 3 sessions had a hazard ratio of 0.73 (0.58–0.92) and those with 4 or more, 0.59 (0.37–0.94).

Notice that here the middle group did reach significance, unlike with the heart and memory. In a separate analysis focused only on pneumonia, in 2,210 men with 375 cases, those with 4 or more sessions a week came in at 0.56 (0.35–0.88) after adjusting for major risk factors; when total dietary energy, socioeconomic status, physical activity and C-reactive protein were added, the figure was 0.63 (0.39–1.00) — right at the edge of significance, and that should be said too.

Why it might work: inflammation

If the sauna does something, how would it do it? The hypothesis with the most support in this same cohort is inflammation.

In 2,269 men, high-sensitivity C-reactive protein, fibrinogen, white blood cells and GGT were measured at baseline and eleven years later. Compared with men who had one session a week, those with 4 to 7 sessions had, at eleven years, C-reactive protein 1.66 mg/L lower, fibrinogen 0.16 g/L lower and white blood cells 0.49 ×10⁹/L lower. All three differences were significant.

And one detail that helps avoid overstating it: GGT, used as a marker of oxidative stress, did not change — neither at baseline nor at eleven years. In other words, the pattern points to less inflammation, not a general antioxidant effect. The authors present it as a hypothesis about the pathway, not as the proven pathway.

There's one more piece that fits. In 2,264 men with 528 cases of pneumonia over 26.6 years, frequent sauna use softened the extra risk that came with high C-reactive protein: men with high inflammation and little sauna use had 1.67 times the risk, while those with high inflammation and frequent sauna use showed no excess risk (0.94; 0.69–1.29).

Alongside exercise, never instead of it

This is the part that decides how to use everything above, and luckily someone measured it directly.

In 2,277 men, fitness was measured for real — with respiratory gas analysis, not a questionnaire — along with sauna frequency. Over a median of 26.1 years there were 520 cardiovascular deaths and 1,124 deaths from any cause. Using men with poor fitness and little sauna use as the reference:

The hazard ratios are 0.42 (0.28–0.62), 0.50 (0.39–0.63) and 0.72 (0.54–0.97). The pattern for death from any cause was the same: 0.60, 0.63 and 0.78.

Read the table from the bottom up and you have the practical conclusion of this article. Sauna alone, without fitness, was linked to a real but modest improvement. Fitness alone was already worth more than sauna alone. And the two together were best of all. A sauna isn't a shortcut around walking, strength training and taking care of your metabolism. It's something that adds to them.

There's a related finding worth mentioning because it speaks to real life. In 2,575 men followed for 27.8 years, low socioeconomic status was linked to 31% higher mortality. But among low-income men who used the sauna often, that excess risk was no longer significant (1.07; 0.89–1.29). In Finland the sauna is cheap and in every home, which makes it one of the few health tools that doesn't cost more for those who have less.

Setting the right expectations

None of the above is a clinical trial. It's observational evidence, and that has three concrete consequences worth keeping in mind:

• Association, not cause. Nobody randomly assigned 2,315 men to "sauna four times a week" or "sauna once" for twenty years. They were asked what they did, and researchers watched what happened to them.
• People who use the sauna more may have been healthier to begin with. This is called reverse causation, and it's the serious problem. A man with a weak heart, who is tired or has an illness on the way, goes to the sauna less. The authors adjusted for a lot — including physical activity, measured fitness and socioeconomic status — and the association survived. That helps, but it isn't the same as a trial.
• The population is specific. Middle-aged Finnish men, using traditional dry sauna, in a culture where it's used from childhood. The only exception is the stroke study, which included women. Whether this applies the same way to a 45-year-old in Miami using a gym sauna twice a week is a reasonable assumption, not a finding.

All that said, for something that is pleasant, inexpensive in its context and low-risk in healthy people, the body of evidence is quite a bit better than that behind many things sold for much more. Placed on the right scale — next to walking, strength and sleep, not above them — the sauna has earned a place with data from real people.

Who is this NOT for?

Heat is a real load on the cardiovascular system. That's exactly why it might help, and also why some people shouldn't go in — or not without talking to their doctor first.

• If you had a recent heart attack, or have unstable angina, the sauna isn't the place to find out. Ask first.
• Severe aortic stenosis or other significant valve disease: the drop in blood pressure in the heat can be dangerous here.
• Uncontrolled high blood pressure. As you saw above, frequent sauna use didn't offset a systolic pressure of 140 or more. Treatment comes first.
• Low blood pressure, dizziness or fainting. Heat lowers blood pressure; if this already happens to you, the two add up.
• Pregnancy. Talk to your obstetrician first; this isn't something to start on your own while pregnant.
• Alcohol: never. This isn't a nuance — it's the most important sauna safety rule. Alcohol dehydrates you, lowers your blood pressure, impairs judgment and removes the warning signal that would tell you to get out.
• Children and frail older adults: much shorter sessions, never alone, and better to ask first.
• If you take medications that affect blood pressure, sweating or fluid balance — diuretics, some blood pressure medications, some psychiatric medications, anticholinergics — ask. It isn't forbidden; it changes how your body handles heat.
• If you're dehydrated, feverish or have an acute infection, not that day.
• If you have a chronic heart, kidney or lung condition, this is a conversation with your doctor, not a decision based on an article.

And the universal signal: if you feel dizzy, short of breath, have chest pain or just feel off — get out. You don't tough out a sauna.

How to do it right

• Hydrate before and after. You'll sweat a lot more than you think. Water, and if you sweat heavily, something with electrolytes.
• Start short. Five to ten minutes the first time is enough. The 19-minute figure comes from men who had been doing this all their lives; it isn't a day-one goal.
• Step out to cool down, and go back in if you want. The Finnish habit is rounds, not one long stay.
• No alcohol. Not before, not inside, and no "cold one afterward" as part of the ritual.
• Don't go alone if you have any heart risk factor or if it's your first time.
• Don't use it to "sweat off weight." What drops on the scale after a sauna is water, and it comes back as soon as you drink. That isn't fat, and chasing it by dehydrating yourself is a bad idea.
• If you train, go afterward, not before. And remember the table: the sauna adds to training; it doesn't replace it.

Where this fits if you're losing weight

It's worth being clear about what the sauna isn't: it isn't a weight-loss treatment, and none of the evidence above measured that. What does overlap is the territory of inflammation and heart health, which is the same territory where weight plays out. A body with less inflammation and better blood pressure is in better shape for any plan, and the sauna is one of the pleasant things you can add to a plan without competing with it.

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Frequently asked questions

How many times a week do you need to go for it to help?

In the evidence, the big difference showed up in the 4-to-7-times-a-week group. The 2-to-3-times group did better than the once-a-week group on almost every outcome, but for the heart and memory that result wasn't statistically significant. The exception was respiratory disease, where 2 to 3 times did give a clear result. If you go twice a week, you're not doing anything wrong; the strongest evidence is simply for going more often.

How long should I stay in?

In the study, sessions longer than 19 minutes were linked to 52% less sudden cardiac death compared with sessions under 11 minutes. But that's in men who had used the sauna all their lives. If you're starting out, five to ten minutes and stepping out to cool down is sensible, and you can build up over time. If you get dizzy, the right number is the one you were at before you got dizzy.

Does a sauna count as exercise?

It resembles exercise in some ways — your pulse rises into the light-to-moderate range and your blood vessels open — but it doesn't replace it, and that has been measured. In the 2,277 men whose fitness was measured with gas analysis, good fitness alone was linked to 50% less cardiovascular death and frequent sauna without good fitness to 28% less. The two together gave 58% less. The sauna adds; it doesn't replace.

I have high blood pressure. Is a sauna a good idea for me?

That's exactly the question to ask your doctor before you start, and the evidence explains why. On one hand, in men without hypertension, frequent sauna use was linked to 46% lower risk of developing it. On the other, in men whose systolic pressure was already 140 or higher, frequent sauna use didn't eliminate the excess risk of cardiovascular death: it stayed at 1.52. So it seems more useful for not getting there than for making up for it once you have. And uncontrolled high blood pressure is on the list of precautions.

Does an infrared sauna work, or does it have to be a Finnish one?

All the evidence you read here is from traditional Finnish dry sauna, at 80–100 °C (176–212 °F) with low humidity. It can't be transferred directly to an infrared sauna, which works at much lower temperatures and heats you differently. It may do similar things, but anyone who tells you it has the same data behind it is stretching the evidence.

Does it really help memory?

What exists is a strong association: in the same cohort, 4 to 7 sessions a week were linked to 66% less dementia and 65% less Alzheimer's. What doesn't exist is a trial proving it, and there's a reasonable alternative explanation: a memory disease that takes decades to develop may be causing someone to use the sauna less, not the other way around. It's a signal that deserves trials, not a conclusion.

Can I have a beer in the sauna?

No. This is the most important precaution of all, and it has no useful exceptions. Alcohol dehydrates you, lowers your blood pressure, impairs judgment and removes the signal that would warn you to get out. The combination of heat and alcohol is behind serious sauna accidents.

What if I sweat off four pounds? Did I lose weight?

You lost water, and it comes back as soon as you drink. It isn't fat. Chasing that number by dehydrating yourself doesn't get you anywhere and can get you into trouble, especially if you take diuretics or blood pressure medication.

Is there any benefit if I can only go once a week?

Once a week was the comparison group in these studies, so there's no data saying "once a week improves on zero." The honest answer is that it wasn't measured. What was measured is that more frequency was linked to better outcomes in a stepwise way, which is the pattern you'd expect if something real were behind it.

Sources

• Laukkanen T, Khan H, Zaccardi F, Laukkanen JA. Association between sauna bathing and fatal cardiovascular and all-cause mortality events. JAMA Intern Med. 2015;175(4):542-548. — DOI
• Kunutsor SK, Khan H, Zaccardi F, Laukkanen T, Willeit P, Laukkanen JA. Sauna bathing reduces the risk of stroke in Finnish men and women: a prospective cohort study. Neurology. 2018;90(22):e1937-e1944. — DOI
• Laukkanen T, Kunutsor S, Kauhanen J, Laukkanen JA. Sauna bathing is inversely associated with dementia and Alzheimer's disease in middle-aged Finnish men. Age Ageing. 2017;46(2):245-249. — DOI
• Zaccardi F, Laukkanen T, Willeit P, Kunutsor SK, Kauhanen J, Laukkanen JA. Sauna bathing and incident hypertension: a prospective cohort study. Am J Hypertens. 2017;30(11):1120-1125. — DOI
• Kunutsor SK, Laukkanen T, Laukkanen JA. Sauna bathing reduces the risk of respiratory diseases: a long-term prospective cohort study. Eur J Epidemiol. 2017;32(12):1107-1111. — DOI
• Kunutsor SK, Laukkanen T, Laukkanen JA. Frequent sauna bathing may reduce the risk of pneumonia in middle-aged Caucasian men: the KIHD prospective cohort study. Respir Med. 2017;132:161-163. — DOI
• Kunutsor SK, Laukkanen T, Laukkanen JA. Longitudinal associations of sauna bathing with inflammation and oxidative stress: the KIHD prospective cohort study. Ann Med. 2018;50(5):437-442. — DOI
• Kunutsor SK, Khan H, Laukkanen T, Laukkanen JA. Joint associations of sauna bathing and cardiorespiratory fitness on cardiovascular and all-cause mortality risk: a long-term prospective cohort study. Ann Med. 2018;50(2):139-146. — DOI
• Kunutsor SK, Jae SY, Laukkanen JA. Frequent sauna bathing offsets the increased risk of death due to low socioeconomic status: a prospective cohort study of middle-aged and older men. Exp Gerontol. 2022;167:111906. — DOI
• Laukkanen JA, Jae SY, Kauhanen J, Kunutsor SK. The interplay between systolic blood pressure, sauna bathing, and cardiovascular mortality in middle-aged and older Finnish men: a cohort study. J Nutr Health Aging. 2023;27(5):348-353. — DOI
• Kunutsor SK, Jae SY, Laukkanen JA. Attenuated risk of pneumonia due to inflammation by frequent sauna baths: a prospective cohort study. J Cardiopulm Rehabil Prev. 2022;42(1):59-63. — DOI
• Laukkanen JA, Laukkanen T, Kunutsor SK. Cardiovascular and other health benefits of sauna bathing: a review of the evidence. Mayo Clin Proc. 2018;93(8):1111-1121. — DOI

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This article is informational and is not medical advice. SCTS1 does not prescribe or dispense medications. All medical care, prescriptions and treatment plans are provided by licensed physicians through our partner platforms. Eligibility for treatment is determined by a licensed provider through medical evaluation. Sauna use is a habit, not a treatment: it is not intended to diagnose, treat, cure or prevent any disease. All evidence cited here is observational and shows associations, not causes, and comes mostly from middle-aged Finnish men using traditional dry sauna. Heat places a load on the cardiovascular system: if you have heart disease, valve disease, uncontrolled high blood pressure, low blood pressure, are pregnant, or take medications that affect blood pressure or fluid balance, talk to your doctor before using a sauna. Never combine sauna and alcohol. If you feel dizzy, short of breath or have chest pain, get out immediately. Results vary from person to person.