Meet the 2,315 Finnish men behind the headlines about saunas and longevity.

The best-known sauna study followed men from one Finnish town for more than twenty years.Source 1 · Cohort studyAssociation Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality EventsLaukkanen T, Khan H, Zaccardi F, et al.. JAMA Internal Medicine, 2015.Read the paper ↗PubMed ↗ Its numbers now turn up on podcasts and on the product pages of sauna brands. Scroll through the men one ember at a time to see where they come from.

By Adam BognarSep 24, 20266 min read

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It starts in Kuopio in 1984

A heart study in eastern Finland asked 2,327 men how often they took a sauna

Researchers recruited middle-aged men from Kuopio and the surrounding countryside between 1984 and 1989, and each man filled in a questionnaire about his sauna habits.Source 1 · Cohort studyAssociation Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality EventsLaukkanen T, Khan H, Zaccardi F, et al.. JAMA Internal Medicine, 2015.Read the paper ↗PubMed ↗ Every point of light on this page is one of those men.

Nearly all of them took saunas

Twelve men never took saunas, so the study left them out

That left 2,315 men and no comparison group of people who avoid the sauna. Every result from here on compares frequent bathers with men who went once a week.Source 1 · Cohort studyAssociation Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality EventsLaukkanen T, Khan H, Zaccardi F, et al.. JAMA Internal Medicine, 2015.Read the paper ↗PubMed ↗

Their answers set the groups

The men split into three groups by how often they went

Weekly bathers made up 601 of the men, and 1,513 went two or three times. The famous numbers come from the 201 men who went four to seven times a week.Source 1 · Cohort studyAssociation Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality EventsLaukkanen T, Khan H, Zaccardi F, et al.. JAMA Internal Medicine, 2015.Read the paper ↗PubMed ↗

The count runs from 1984 to 2011

The researchers followed every man through national death records

Scroll slowly. Each ember goes out when a man in its group dies.

The totals at the end match the paper.Source 1 · Cohort studyAssociation Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality EventsLaukkanen T, Khan H, Zaccardi F, et al.. JAMA Internal Medicine, 2015.Read the paper ↗PubMed ↗ It reports only those final counts, so we spread the deaths across the years ourselves.

The records close in 2011

The men who took the most saunas died least often

By 2011, 49% of the once-a-week men had died. It was 38% in the middle group and 31% in the top group.Source 1 · Cohort studyAssociation Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality EventsLaukkanen T, Khan H, Zaccardi F, et al.. JAMA Internal Medicine, 2015.Read the paper ↗PubMed ↗

Headlines quoted a 40% lower risk of death for the top group. The researchers got that figure after adjusting for age, fitness, smoking, socioeconomic status and other differences between the men.

Rewind to the start

The most frequent bathers started out healthier

They were younger and fitter than the weekly bathers, and 20% of them smoked, against 36% of the weekly men.Source 1 · Cohort studyAssociation Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality EventsLaukkanen T, Khan H, Zaccardi F, et al.. JAMA Internal Medicine, 2015.Read the paper ↗PubMed ↗ Statistics can only correct for the differences a study measures, and a questionnaire from 1984 left plenty unmeasured.

The paper counts sudden heart deaths

The famous 63% drop in sudden cardiac death comes down to ten men

Ten of the 201 frequent bathers died suddenly of heart problems, against 61 of the 601 weekly bathers. A few deaths either way would move that 63% a long way. On a scale where 1 means no difference, the paper puts the plausible range at 0.18 to 0.75.Source 1 · Cohort studyAssociation Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality EventsLaukkanen T, Khan H, Zaccardi F, et al.. JAMA Internal Medicine, 2015.Read the paper ↗PubMed ↗

Fitness enters the picture

Fitter men who took fewer saunas did better than less fit men who took more

A 2018 analysis sorted 2,291 of the men by measured fitness as well as by sauna habit. Sudden cardiac death struck 5.5% of the fitter men who took two or fewer saunas a week. The rate was 11.0% for less fit men who took three to seven.Source 2 · Cohort studyCombined Effect of Sauna Bathing and Cardiorespiratory Fitness on the Risk of Sudden Cardiac Deaths in Caucasian Men: A Long-term Prospective Cohort StudyLaukkanen JA, Laukkanen T, Khan H, et al.. Progress in Cardiovascular Diseases, 2018.Read the paper ↗PubMed ↗

Once the researchers accounted for fitness, the link with sauna was too weak to rule out chance.

The records run on to 2018

With longer follow-up the difference shrank to 14%

A 2022 analysis tracked 2,575 men from the same study through 2018 and split them at three saunas a week. Men who went three to seven times had a 14% lower risk of death than the rest.Source 3 · Cohort studyInflammation, sauna bathing, and all-cause mortality in middle-aged and older Finnish men: a cohort studyKunutsor SK, Jae SY, Kurl S, et al.. European Journal of Epidemiology, 2022.Read the paper ↗PubMed ↗

By then 56% of them had died, against 65% of the men who went less often.Source 4 · Cohort studyFrequent sauna bathing offsets the increased risk of death due to low socioeconomic status: A prospective cohort study of middle-aged and older menKunutsor SK, Jae SY, Laukkanen JA. Experimental Gerontology, 2022.Read the paper ↗PubMed ↗

Women join the study in 1998

The link with fewer heart deaths didn't show up in women

In this later sample of 1,688 men and women, the result came from the men. Women who went two or three times a week did no better than women who went once.Source 5 · Cohort studySauna bathing is associated with reduced cardiovascular mortality and improves risk prediction in men and women: a prospective cohort studyLaukkanen T, Kunutsor SK, Khan H, et al.. BMC Medicine, 2018.Read the paper ↗PubMed ↗

The 73 women in the top group had no heart deaths at all. With no deaths to count, the researchers couldn't estimate their risk.

The study links frequent saunas to fewer deaths in one group of Finnish men

The Finnish men who took the most saunas did die less often, and the link held after the researchers accounted for fitness, smoking, blood pressure and socioeconomic status. It shrank with longer follow-up and disappeared in the fittest men.Source 1 · Cohort studyAssociation Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality EventsLaukkanen T, Khan H, Zaccardi F, et al.. JAMA Internal Medicine, 2015.Read the paper ↗PubMed ↗Source 3 · Cohort studyInflammation, sauna bathing, and all-cause mortality in middle-aged and older Finnish men: a cohort studyKunutsor SK, Jae SY, Kurl S, et al.. European Journal of Epidemiology, 2022.Read the paper ↗PubMed ↗Source 6 · Cohort studyJoint associations of sauna bathing and cardiorespiratory fitness on cardiovascular and all-cause mortality risk: a long-term prospective cohort studyKunutsor SK, Khan H, Laukkanen T, et al.. Annals of Medicine, 2018.Read the paper ↗PubMed ↗ All of this comes from one group of middle-aged Finnish men. No trial has assigned people to saunas at random and then counted deaths.

Sauna looks like a habit with a plausible upside for the heart. In the same men, measured fitness predicted survival more strongly.Source 6 · Cohort studyJoint associations of sauna bathing and cardiorespiratory fitness on cardiovascular and all-cause mortality risk: a long-term prospective cohort studyKunutsor SK, Khan H, Laukkanen T, et al.. Annals of Medicine, 2018.Read the paper ↗PubMed ↗ You'll find the numbers behind the other heart claims on the claims page.

36°H

Likely

Heat

“Regular sauna use helps you live longer.”

One long-running Finnish study ties frequent sauna use to fewer deaths. The 2015 paper put the most frequent bathers' risk of death 40% lower, and later papers with longer follow-up and broader groups put it about 14% lower. The link didn't show up in the fitter half of the men or in the women the study added later.

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