Sauna and blood pressure: what a 25-year study found
Finnish men who used the sauna more often were less likely to develop high blood pressure over the next quarter-century. The result is notable, but the statistical margin is narrow enough to treat with caution.
The short version
Researchers followed 1,621 Finnish men without high blood pressure for a median of 24.7 years, the longest follow-up of any study in this library. Men who reported four to seven sauna sessions a week later developed high blood pressure less often than men who reported one session a week. After full adjustment, the difference was statistically significant but close to the margin: the confidence interval nearly touched the point of no difference. This was an observational study of men only, so it cannot show that sauna use itself prevented anyone’s hypertension.
Keep in mind
An association in men only, and the confidence interval (0.28 to 0.98) sits close to the line of no effect: a narrower margin than the other KIHD findings in this library.
What they found
251 men (15.5%) developed high blood pressure during follow-up. Men who reported four to seven sauna sessions a week had a lower rate of new hypertension than men who reported one session a week: a fully adjusted hazard ratio of 0.53 (95% confidence interval 0.28 to 0.98).
That confidence interval is wide and its upper edge, 0.98, sits just under the point of no difference at all. The true association could be close to zero.
The pattern followed a similar step-up across the sauna-frequency groups the researchers compared.
What this means for your practice
This is a promising but statistically narrow finding about a group of Finnish men, not a guarantee for any individual. It is not a reason to stop or delay blood pressure treatment.
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 original eastern Finland KIHD cohort (the same group of men as our 2015 heart-health article), restricted to 1,621 men aged 42 to 60 who did not have high blood pressure at the start.
They recorded how often each man used a sauna, then tracked new diagnoses of high blood pressure for a median of 24.7 years, the longest follow-up of any study in this library.
The analysis adjusted for age, smoking, body mass index and starting blood pressure, then added further adjustment for blood glucose, kidney markers, alcohol use, heart rate, family history of hypertension, socioeconomic status and fitness.
How much can this tell us?
The 24.7-year follow-up and the clear endpoint (a new diagnosis of hypertension) are real strengths. So is having a defined starting point: everyone was free of high blood pressure at baseline.
But the confidence interval’s upper bound (0.98) is close enough to 1.0 that the association is only borderline statistically significant. A slightly different sample could plausibly have shown no association at all.
This is the same men-only KIHD cohort as our 2015 heart-health article (ages 42–60), not the later cohort that added women. Sauna habits were recorded once, and only men took part.
What makes it useful
- Longest follow-up of any study in this library: 24.7 years
- Clear endpoint: a new diagnosis of high blood pressure
- Extensive adjustment for other risk factors
What limits it
- Observational: an association, not proof of cause
- Confidence interval sits close to the line of no effect
- Men only; sauna habits recorded once, at the start
Where this study fits
Where this study fits
We score claims, not single studies. This one is part of the evidence for:
Regular sauna keeps blood pressure down over the years. Early signal
Very low certaintyMedium effectIllness and death
High blood pressure 47% fewer
Likely 2% to 72%
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
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 10.1093/ajh/hpx102