December 19, 2016

Sauna and dementia

Q: Did you see that saunas prevent dementia?

A: Well, even the Herald headline only says “could cut risk

Q: You don’t sound convinced.

A: No.

Q: Is this mice again?

A: No, I don’t think there are good animal models for saunas.

Q: Would it be inappropriate to attempt some sort of double entendre here?

A: Yes. The Finns would be offended.

Q: Ok. Back to business. You’re going to tell me that the research paper doesn’t make these claims and it’s all the fault of the British media, right?

A: No, the research paper has as one of its Key Points “Sauna bathing, an activity that promotes relaxation and well-being, may be a recommendable intervention to prevent or delay the development of memory diseases in healthy adults.”

Q: That’s pretty positive.

A: And the university press release is titled “Frequent sauna bathing protects men against dementia

Q: Is this one of those things that’s statistically significant but too small to care about?

A: No, they’re claiming a 2/3 reduction in dementia risk.

Q: Wow. That’s…umm…?

A: Larger than one would reasonably expect?

Q: Very diplomatically put.  Wait, so if that was true, you’d be able to see it in the national figures. Does Finland have a much lower dementia rate than you’d otherwise expect?

A: An excellent question.  No.

Q: [citation needed]

A: Well, ok, diagnosis bias makes it tricky, but the Institute for Health Metrics and Evaluation is making serious attempts to do international comparisons on all sorts of disease, and they think Finland has higher rates than expected, in contrast to the rest of Scandinaviasauna-alz

Q: So sauna isn’t protective?

A: Well, it’s not hugely, implausibly protective unless there’s some other Finland-specific risk factor that cancels it out



Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »


  • avatar
    Megan Pledger

    Pretty much everyone will get alzheimers or dementia if they live long enough. If could be that Finnish men (people?) are living long enough e.g. they die at 100 with dementia rather than at 71 with a heart attack.

    So, I guess, age. (Unless the rates are age stratified.)

    9 months ago

    • avatar
      Thomas Lumley

      The observed/expected ratio is age-adjusted. They’re epidemiologists. They age-adjust everything as a basic reflex.

      (And I wouldn’t expect Finland to be much older than the rest of Scandinavia)

      9 months ago

  • avatar
    steve curtis

    Wouldnt jockeys be the group to study here as I understand they use saunas compulsively to keep their weight down, especially in the few days before the race weigh-in.

    9 months ago

    • avatar
      Thomas Lumley

      Well, it depends on the hypothesised mechanism. The Finnish researchers think it’s relaxation, which might not work for the jockeys.

      There is a definite advantage to looking at a population where very high sauna use is common across a range of jobs and lifestyles.

      9 months ago