Kuopio men who took four to seven saunas a week had fewer dementia diagnoses
The 66% dementia figure comes from this 2017 paper in Age and Ageing. It matched the sauna habits of 2,315 middle-aged Finnish men against dementia diagnoses over two decades.
The paper
Sauna bathing is inversely associated with dementia and Alzheimer's disease in middle-aged Finnish men
Laukkanen T, Kunutsor S, Kauhanen J, Laukkanen JA. Age and Ageing, 2017;46(2):245-249.
See the study at a glance
- Design
- Prospective cohort study
- People
- 2,315 men
- Who they were
- Researchers examined men aged 42 to 60 from Kuopio and nearby rural areas between 1984 and 1989. These are the same men behind the 2015 mortality study, and about a quarter had coronary heart disease at the start.
- What they did
- Each man answered one questionnaire at the start about how many saunas he took a week. The answers were grouped from once a week up to four to seven times. Dementia and Alzheimer's diagnoses came from health registries and medical records through 2013.
- How long
- Median 20.7 years
These numbers came out of it
0.34
Men who went four to seven times a week had this hazard ratio for dementia. Compared with men who went once a week, that's a 66% lower risk.
8
Men in the top group developed dementia, and the 66% figure comes from those eight cases.
0.35
The top group's hazard ratio for Alzheimer's disease comes from only five diagnoses.
0.78
Men who went two or three times a week had this hazard ratio for dementia, and its plausible range included no effect.
Hazard ratio with 95% confidence interval
Only the top group showed a clear drop in dementia risk
The model adjusted for age, body mass index, systolic blood pressure, LDL cholesterol, smoking, alcohol, previous heart attack, type 2 diabetes and resting heart rate. It left out physical activity and socioeconomic status.
The researchers did this
This paper went back to the 2,315 Kuopio men from the 2015 mortality study and checked whether the most frequent bathers developed dementia less often.Source 1 · Cohort studySauna bathing is inversely associated with dementia and Alzheimer's disease in middle-aged Finnish menLaukkanen T, Kunutsor S, Kauhanen J, et al.. Age and Ageing, 2017.Read the paper ↗PubMed ↗ One questionnaire at the start recorded each man's sauna habits. The researchers traced dementia and Alzheimer's diagnoses through registries and medical records up to 2013.
Over a median of 20.7 years, 204 men developed dementia and 123 developed Alzheimer's disease. Among weekly bathers, 10% were diagnosed with dementia (59 men). In the men who went four to seven times a week, the share was 4% (8 men).Source 1 · Cohort studySauna bathing is inversely associated with dementia and Alzheimer's disease in middle-aged Finnish menLaukkanen T, Kunutsor S, Kauhanen J, et al.. Age and Ageing, 2017.Read the paper ↗PubMed ↗
Once the researchers accounted for age, blood pressure, cholesterol, smoking, alcohol and other heart risk factors, men in the top group had about a third of the weekly bathers' risk. The hazard ratios were 0.34 for dementia and 0.35 for Alzheimer's disease. At two or three sessions a week the estimates came out near 0.8, and their plausible ranges included no effect. According to the text, adding physical activity and socioeconomic status left the results similar, although the table doesn't show that model.
The paper describes the men as apparently healthy, yet its own table shows that 23.9% had coronary heart disease and 7.5% had heart failure at the start. It reports no memory testing at the start, so there's no way to know whether men with early memory problems had already cut back on saunas.Source 1 · Cohort studySauna bathing is inversely associated with dementia and Alzheimer's disease in middle-aged Finnish menLaukkanen T, Kunutsor S, Kauhanen J, et al.. Age and Ageing, 2017.Read the paper ↗PubMed ↗
The study can't tell you these things
- The study recorded habits and assigned nothing, so it can't separate saunas from the things that travel with them. In this group of men, frequent bathers were fitter than weekly bathers and smoked less often.Source 2 · Cohort studyAssociation Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality EventsLaukkanen T, Khan H, Zaccardi F, et al.. JAMA Internal Medicine, 2015.Read the paper ↗PubMed ↗
- Only 8 dementia cases and 5 Alzheimer's cases in the top group produced the headline ratios.
- The men reported their sauna habits once, back in the 1980s. Dementia diagnoses came from registry records, and the study gave no memory tests at the start.
- A separate Finnish study of 13,994 adults found no link in its most frequent bathers.Source 3 · Cohort studyDoes sauna bathing protect against dementia?Knekt P, Järvinen R, Rissanen H, et al.. Preventive Medicine Reports, 2020.Read the paper ↗PubMed ↗
- Some of the paper's numbers don't match. The text puts 200 men in the top group where the table has 201, and the Alzheimer's interval appears as both 0.14 to 0.90 and 0.16 to 0.90.
People quote it like this
The claim that sauna cuts dementia risk by 66% and Alzheimer's risk by 65% comes from this paper. The authors' 2024 review repeats both figures. It also cites the separate Finnish study without mentioning that its most frequent bathers showed no benefit or what it found for saunas above 100°C.Source 4 · ReviewThe multifaceted benefits of passive heat therapies for extending the healthspan: A comprehensive review with a focus on Finnish saunaLaukkanen JA, Kunutsor SK. Temperature, 2024.Read the paper ↗PubMed ↗Source 3 · Cohort studyDoes sauna bathing protect against dementia?Knekt P, Järvinen R, Rissanen H, et al.. Preventive Medicine Reports, 2020.Read the paper ↗PubMed ↗
From our sister magazine
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We cited these sources
- 01Laukkanen 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. doi:10.1093/ageing/afw212 PMID 27932366
- 02Laukkanen 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. doi:10.1001/jamainternmed.2014.8187 PMID 25705824
- 03Knekt P, Järvinen R, Rissanen H, Heliövaara M, Aromaa A. Does sauna bathing protect against dementia?. Preventive Medicine Reports. 2020;20:101221. doi:10.1016/j.pmedr.2020.101221 PMID 33088678
- 04Laukkanen JA, Kunutsor SK. The multifaceted benefits of passive heat therapies for extending the healthspan: A comprehensive review with a focus on Finnish sauna. Temperature. 2024;11(1):27-51. doi:10.1080/23328940.2023.2300623 PMID 38577299