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The Same Finnish Men Who Saunaed Most Had 66% Less Dementia. Nobody Expected That
The researchers went looking at hearts. The memory finding came out of the same 2,315 men, and it was the first study of its kind.
This finding came out of a study that was not looking for it.
The Kuopio cohort was built to study heart disease. The men were enrolled in the 1980s, their sauna habits recorded almost incidentally, and the cardiovascular results published first. Then somebody asked a different question of the same data.
What they found
Among the same 2,315 apparently healthy Finnish men, aged 42 to 60, followed for a median of 20.7 years, there were 204 diagnosed cases of dementia and 123 of Alzheimer’s disease (Laukkanen et al., Age and Ageing, 2017).
Adjusted for age, alcohol consumption, body mass index, systolic blood pressure, smoking, type 2 diabetes, previous myocardial infarction, resting heart rate and LDL cholesterol, compared with one sauna session a week:
| Sessions per week | Dementia | Alzheimer’s disease |
|---|---|---|
| 2 to 3 | HR 0.78 (0.57 to 1.06) | HR 0.80 (0.53 to 1.20) |
| 4 to 7 | HR 0.34 (0.16 to 0.71) | HR 0.35 (0.14 to 0.90) |
A 66% lower hazard for dementia and 65% for Alzheimer’s, in the most frequent group.
Read the confidence intervals before you get excited
Look at that Alzheimer’s interval again: 0.14 to 0.90.
That is a wide range, and it is wide because the four-to-seven group was only about 200 men. The true effect could plausibly be enormous or fairly modest. What the interval does tell you is that it stayed on the protective side of 1.0, which is why it reached significance at all.
The two-to-three group did not reach significance for either outcome. The signal lives almost entirely in the most frequent users.
And the authors say the quiet part out loud: there were no previous studies linking repeated sauna heat exposure to memory disease risk. This was first of its kind. First findings are how research starts, not how it ends.
In this male population, moderate to high frequency of sauna bathing was associated with lowered risks of dementia and Alzheimer's disease. Further studies are warranted to establish the potential mechanisms.
Laukkanen et al., Age and Ageing, 2017
The confounder nobody can adjust away
A man who sits in 90 degree heat four to seven times a week for twenty years is telling you something about himself beyond his sauna habit.
He is well enough to do it. He probably has a home with a sauna, or a community with one, which says something about money and about company. He is, on average, not isolated.
Social connection, wealth and baseline health all track with dementia risk independently. The adjustment list in this study is long and serious, and it still cannot fully separate the heat from the life the heat sits inside.
This is the same caution we applied to the cardiovascular findings from this cohort, and it applies with more force here, because cognitive decline has a longer and messier causal chain than a heart attack does.
What might actually be happening
If the effect is real, the leading candidate is not mysterious.
Dementia risk tracks cardiovascular risk closely. Blood pressure, vessel health and blood flow to the brain are shared machinery. A habit that plausibly helps the heart has an obvious route to helping the brain, and this same cohort found the cardiovascular association first.
That is mechanism reasoning rather than proof, and we are flagging it as such. Nobody has shown the chain from sauna to vessel to neuron in a trial.
What we are and are not saying
| Claim | Our line |
|---|---|
| Sauna prevents dementia or Alzheimer’s | Never |
| 4 to 7 sessions a week tracked with HR 0.34 for dementia | Yes, with the interval and the cohort design stated |
| The finding is strong and settled | No. First of its kind, wide intervals, one population, men only |
| It is worth further study | Yes, and the authors say so themselves |
| You should buy a sauna to protect your memory | No. Movement, sleep and blood pressure have better evidence |
Where the design shows up
There is a pattern in this work that keeps surfacing: the things that help one system tend to help several.
Heat, movement, sleep, what is on the plate. None of them are targeted at a single organ, and the benefits keep showing up in places nobody was measuring. That is not how a drug behaves. It is how maintenance behaves.
A body is not a collection of separate machines that happen to share a skin.
“I will give thanks to You, for I am fearfully and wonderfully made.” Psalm 139:14, NASB
The verse carries the conviction. Two hundred and four cases over two decades carry the number, wide intervals and all.
What to do this week
Use the heat you already have, and do not buy anything on the strength of one cohort.
If a sauna is available to you, this is a reason to use it more often rather than longer, same as the cardiovascular data suggested.
If it is not, the interventions with the strongest evidence for cognitive ageing are the unglamorous ones: keep moving, sleep properly, get blood pressure treated, and get hearing checked. None of them require a cabin.
Read this next: the cardiovascular findings from this same cohort, which came first and are better established: men who used a sauna 4 to 7 times a week had 63% fewer sudden cardiac deaths. And for what happens in your body during a first session, new to saunas.
Sources
- 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 and Ageing, 2017;46(2):245-249. https://pubmed.ncbi.nlm.nih.gov/27932366/
- Laukkanen T, Khan H, Zaccardi F, Laukkanen JA. “Association between sauna bathing and fatal cardiovascular and all-cause mortality events.” JAMA Internal Medicine, 2015;175(4):542-548. https://pubmed.ncbi.nlm.nih.gov/25705824/
- Laukkanen 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. https://pubmed.ncbi.nlm.nih.gov/30486813/
Article metadata retrieved from PubMed. Scripture quoted from the New American Standard Bible.
Educational content from True Health Solutions. We do not diagnose or prescribe, and nothing here is a substitute for care from someone who knows your history. The body heals. We write about what supports that design.
Questions people ask
- Is there a link between sauna use and dementia?
- In one Finnish cohort, yes. Among 2,315 men followed for a median of 20.7 years, those using a sauna 4 to 7 times a week had a hazard ratio of 0.34 for dementia and 0.35 for Alzheimer's disease compared with once a week, after adjustment. That is an association in one population, not proof.
- How many cases were there?
- 204 diagnosed cases of dementia and 123 of Alzheimer's disease over the follow-up period. The confidence intervals on the strongest findings are wide, which is what you would expect from a subgroup of about 200 men.
- Was this the first study of its kind?
- The authors state plainly that there were no previous studies linking repeated heat exposure of sauna and the risk of memory diseases. A first finding is a reason to look further, not a reason to conclude.
- Could this just be that healthier men use saunas more?
- That is the central problem with any observational cohort, and it is why we will not call this proof. The analysis adjusted for age, alcohol, BMI, blood pressure, smoking, type 2 diabetes, previous heart attack, resting heart rate and LDL cholesterol. Adjustment reduces confounding. It does not eliminate it.
- What should I actually do with this?
- Treat it as one more reason to use heat if you already have access to it, and not as a reason to expect protection from a disease. The things with stronger evidence for cognitive ageing are movement, sleep, blood pressure and hearing, and all of them are free or cheap.
