Sauna and stroke: what a long Finnish study found
A Finnish study of 1,628 men and women linked more frequent sauna use with fewer strokes over nearly 15 years. The original paper describes this as reducing risk; because the design is observational, we describe it as an association.
The short version
Researchers followed 1,628 Finnish men and women for a median of 14.9 years and recorded 155 strokes. People who reported four to seven sauna sessions a week had a lower stroke rate than people who reported one session a week, even after adjusting for cardiovascular risk factors, activity and socioeconomic status. The pattern was similar for ischemic stroke; for the rarer hemorrhagic type, the evidence was thinner. Participants chose their own sauna habits and were asked only once, so this observational study cannot prove that sauna use itself lowered anyone’s risk.
Keep in mind
An association, not proof of cause and effect. Sauna habits were self-reported once, at the start, and the evidence for hemorrhagic stroke specifically is thinner.
What they found
155 strokes occurred during follow-up. People who reported four to seven sauna sessions a week had a lower stroke rate than people who reported one session a week: a fully adjusted hazard ratio of 0.38 (95% confidence interval 0.18 to 0.81).
The association was similar whether the researchers adjusted lightly (for age and sex) or more fully (adding risk factors, activity and socioeconomic status). The hazard ratio barely moved.
The pattern was consistent for ischemic stroke. For hemorrhagic stroke it was weaker and less certain, which the researchers attribute to the small number of those events (34).
What this means for your practice
This is a consistent, well-adjusted association from one Finnish cohort. It is not evidence that a specific sauna routine prevents stroke, and the frequencies above are comparison groups from the study, not advice.
This does not establish a sauna routine to follow, or show that a KUUME ritual has these effects.
Methods and limitations
What the researchers did
Researchers used the same later KIHD examination as our heart-health-in-women article: 1,628 men and women in eastern Finland, aged 53 to 74, with no known history of stroke at the start. They asked how often each person used a sauna and grouped them into three categories: one, two to three, or four to seven sessions a week.
Strokes were then tracked for a median of 14.9 years through Finnish health records, without asking anyone to change their habits.
The researchers adjusted for age, sex and established cardiovascular risk factors, then separately for physical activity and socioeconomic status, to see whether the pattern held up.
How much can this tell us?
The published paper’s own title says sauna bathing “reduces” stroke risk. Because sauna habits were not randomly assigned, we describe this as an association rather than a cause, in line with how we read every observational study in this library.
The hazard ratio changing very little across different adjustment models is a real strength: it suggests the association is not easily explained away by the factors the researchers could measure. It cannot rule out factors they did not measure.
This uses the same later KIHD examination (ages 53–74, including women) as our heart-and-women article, not the 2,315 men from 2015. See that article’s note on the two cohorts.
What makes it useful
- 1,628 people, median follow-up of 14.9 years
- Hazard ratio changed little across adjustment models
- Includes both men and women
What limits it
- Observational: an association, not proof of cause
- Sauna habits self-reported once, at the start
- Hemorrhagic stroke evidence is thinner (34 events)
Where this study fits
Where this study fits
We score claims, not single studies. This one is part of the evidence for:
Regular sauna means fewer strokes. Some support
Low certaintyLarge effectIllness and death
Stroke 62% fewer
Likely 19% to 82%
Fewer cases than the comparison group. The bar is the best estimate, the band behind it the likely range.
From the same participant group as 7 other articles in The Study, so we count them as one group of people.
Read the original
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 10.1212/WNL.0000000000005606 · PubMed 29720543