Finnish adults who took the most saunas had fewer strokes over 15 years
Neurology published this study of 1,628 men and women in eastern Finland in 2018, and the 61% stroke figure comes from it. Most of the detail is behind the journal's paywall.
The paper
Sauna bathing reduces the risk of stroke in Finnish men and women
Kunutsor SK, Khan H, Zaccardi F, Laukkanen T, et al.. Neurology, 2018;90(22):e1937-e1944.
See the study at a glance
- Design
- Prospective cohort study
- People
- 1,628 men and women
- Who they were
- The participants were Kuopio study members aged 53 to 74 (average 62.7). None had had a stroke when they were examined between 1998 and 2001.
- What they did
- People reported their weekly sauna sessions on a questionnaire at the 1998 to 2001 examination. The headline result compares four to seven sessions a week with one.
- How long
- Median 14.9 years
These numbers came out of it
0.39
People who went four to seven times a week had this hazard ratio for stroke once age and sex were accounted for. It's where the 61% lower risk comes from.
0.38
Taking physical activity and socioeconomic status into account as well nudged the ratio to this.
155
People had a stroke during follow-up. The abstract doesn't break that number down by sauna group.
0.33
The authors' later review gave this hazard ratio for stroke caused by bleeding (hemorrhagic stroke). Its plausible range runs from 0.07 to 1.51.
Hazard ratio with 95% confidence interval, four to seven a week against one
The top group's stroke risk barely moved as more factors were taken into account
The ischemic and hemorrhagic rows come from the summary table in the authors' 2018 Mayo Clinic Proceedings review. Its counts for the two types add up to 163, though the paper itself reports 155 strokes.
The researchers did this
The Kuopio study added women at a follow-up examination between 1998 and 2001. This paper took the 1,628 men and women examined then who had never had a stroke and linked their sauna habits to strokes over a median of 14.9 years.Source 1 · Cohort studySauna bathing reduces the risk of stroke in Finnish men and womenKunutsor SK, Khan H, Zaccardi F, et al.. Neurology, 2018.Read the paper ↗PubMed ↗
By the end, 155 people had had a stroke. Allowing for age and sex, people who went four to seven times a week had a hazard ratio of 0.39 compared with people who went once. The estimate barely moved as the researchers added standard heart risk factors and then physical activity and socioeconomic status. It finished at 0.38. The link looked the same across ages and in both sexes.Source 1 · Cohort studySauna bathing reduces the risk of stroke in Finnish men and womenKunutsor SK, Khan H, Zaccardi F, et al.. Neurology, 2018.Read the paper ↗PubMed ↗
Neurology keeps the full text behind a paywall. The abstract doesn't give the size of each sauna group, the number of strokes in each, the estimate for two or three sessions a week or the full list of adjustments. A 2026 review puts the three groups at 26.7%, 61.9% and 12.1% of participants.Source 2 · ReviewEffects of Bathtub Bathing and Sauna Practices on Cardiovascular and Systemic Health: A Narrative ReviewNagai M, Tanaka A. International Journal of Environmental Research and Public Health, 2026.Read the paper ↗PubMed ↗ We couldn't check those shares against the paper.
The authors' 2018 review gave a hazard ratio of 0.42 for ischemic stroke (the kind caused by a blocked artery) and 0.33 for hemorrhagic stroke.Source 3 · ReviewCardiovascular and Other Health Benefits of Sauna Bathing: A Review of the EvidenceLaukkanen JA, Laukkanen T, Kunutsor SK. Mayo Clinic Proceedings, 2018.Read the paper ↗PubMed ↗ The plausible range for the bleeding kind runs from 0.07 to 1.51 and includes no effect, even though the review's text calls the link similar for both types.
Two letters in Neurology challenged the paper. Dippel and colleagues argued that healthy-user bias (frequent bathers being healthier to begin with) could explain it, since sauna use has shown similar links with Alzheimer's disease and respiratory illness.Source 4 · ReviewReader response: Sauna bathing reduces the risk of stroke in Finnish men and women: A prospective cohort studyDippel DW, Fransen PS, Ikram MK. Neurology, 2019.Read the paper ↗PubMed ↗ Yu and colleagues worried that heat and fluid loss could harm older people with undetected narrowing of the arteries to the brain.Source 5 · ReviewReader response: Sauna bathing reduces the risk of stroke in Finnish men and women: A prospective cohort studyYu Y, Guo WT, Yan XL, et al.. Neurology, 2019.Read the paper ↗PubMed ↗ The authors replied that the result held after they excluded the first two years of follow-up and people with existing disease, and they agreed that studies like theirs can't prove cause and effect.Source 6 · ReviewAuthor response: Sauna bathing reduces the risk of stroke in Finnish men and women: A prospective cohort studyKunutsor SK, Laukkanen T, Laukkanen JA. Neurology, 2019.Read the paper ↗PubMed ↗
The study can't tell you these things
- The abstract doesn't give group sizes or strokes per group, so without the full text you can't work out how many strokes the 61% stands for.
- It can only show a link, and frequent bathers differed in other ways. At the same examination they were far more likely than weekly bathers to live in a family house.Source 7 · 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 ↗
- People were asked about sauna habits once. As the critics pointed out, risk factors can change a great deal over 14 years.Source 4 · ReviewReader response: Sauna bathing reduces the risk of stroke in Finnish men and women: A prospective cohort studyDippel DW, Fransen PS, Ikram MK. Neurology, 2019.Read the paper ↗PubMed ↗
- The figures for each type of stroke come from the authors' review. Its counts add up to more strokes than the paper reports.Source 3 · ReviewCardiovascular and Other Health Benefits of Sauna Bathing: A Review of the EvidenceLaukkanen JA, Laukkanen T, Kunutsor SK. Mayo Clinic Proceedings, 2018.Read the paper ↗PubMed ↗
- This is the only long-term sauna study to track strokes. A Japanese study of hot-tub bathing found a weaker link, and it stopped being statistically significant once the first ten years were left out.Source 8 · Cohort studyHabitual tub bathing and risks of incident coronary heart disease and strokeUkai T, Iso H, Yamagishi K, et al.. Heart, 2020.Read the paper ↗PubMed ↗
People quote it like this
Neurology's website linked to a patient page that presented the result as regular sauna use lowering the risk of a first stroke. Later, the Kuopio group's own review called the result similar across stroke types, even though its estimate for bleeding strokes wasn't significant.Source 3 · ReviewCardiovascular and Other Health Benefits of Sauna Bathing: A Review of the EvidenceLaukkanen JA, Laukkanen T, Kunutsor SK. Mayo Clinic Proceedings, 2018.Read the paper ↗PubMed ↗
We cited these sources
- 01Kunutsor SK, Khan H, Zaccardi F, Laukkanen T, Willeit P, Laukkanen JA. Sauna bathing reduces the risk of stroke in Finnish men and women. Neurology. 2018;90(22):e1937-e1944. doi:10.1212/WNL.0000000000005606 PMID 29720543
- 02Nagai M, Tanaka A. Effects of Bathtub Bathing and Sauna Practices on Cardiovascular and Systemic Health: A Narrative Review. International Journal of Environmental Research and Public Health. 2026;23(3):347. doi:10.3390/ijerph23030347 PMID 41899724
- 03Laukkanen JA, Laukkanen T, Kunutsor SK. Cardiovascular and Other Health Benefits of Sauna Bathing: A Review of the Evidence. Mayo Clinic Proceedings. 2018;93(8):1111-1121. doi:10.1016/j.mayocp.2018.04.008 PMID 30077204
- 04Dippel DW, Fransen PS, Ikram MK. Reader response: Sauna bathing reduces the risk of stroke in Finnish men and women: A prospective cohort study. Neurology. 2019;92(4):205. doi:10.1212/WNL.0000000000006808 PMID 30665915
- 05Yu Y, Guo WT, Yan XL, Guo ZN, Yang Y. Reader response: Sauna bathing reduces the risk of stroke in Finnish men and women: A prospective cohort study. Neurology. 2019;92(4):204. doi:10.1212/WNL.0000000000006807 PMID 30665914
- 06Kunutsor SK, Laukkanen T, Laukkanen JA. Author response: Sauna bathing reduces the risk of stroke in Finnish men and women: A prospective cohort study. Neurology. 2019;92(4):205-206. doi:10.1212/WNL.0000000000006809 PMID 30665916
- 07Laukkanen T, Kunutsor SK, Khan H, Willeit P, Zaccardi F, Laukkanen JA. Sauna bathing is associated with reduced cardiovascular mortality and improves risk prediction in men and women: a prospective cohort study. BMC Medicine. 2018;16(1):219. doi:10.1186/s12916-018-1198-0 PMID 30486813
- 08Ukai T, Iso H, Yamagishi K, Saito I, Kokubo Y, Yatsuya H, et al.. Habitual tub bathing and risks of incident coronary heart disease and stroke. Heart. 2020;106(10):732-737. doi:10.1136/heartjnl-2019-315752 PMID 32209614