Is Sauna Good for the Brain? Sauna, Dementia Risk and IQ

Sauna may be good for the brain in later life, but the evidence is observational and no study has tested whether it raises IQ. In the best-known study, Finnish men who used a sauna four to seven times a week had about a third of the dementia risk of men who went once a week (hazard ratio 0.34) over roughly 20 years, a result that cannot by itself show that the sauna caused the difference.

Sauna bathing is a weekly habit for many people in Finland and an increasingly popular wellness trend elsewhere. This page covers the Finnish cohort studies behind the claim, why they are hard to interpret, what heat does to thinking in the short term, the evidence for brain chemicals such as BDNF, and basic safety. It describes research and is not medical advice.

Almost everything written about sauna and the brain traces back to two Finnish cohorts.

• Kuopio Ischaemic Heart Disease study (KIHD): Laukkanen and colleagues asked 2,315 apparently healthy men aged 42 to 60 how often they used a sauna, at examinations between 1984 and 1989, and followed them for a median of 20.7 years. During that time 204 men were diagnosed with dementia and 123 with Alzheimer's disease. Compared with men who had one sauna session a week, the hazard ratio for dementia was 0.78 for two to three sessions (not statistically significant) and 0.34 for four to seven sessions. The figures for Alzheimer's disease were similar (0.80 and 0.35).

• Finnish Mobile Clinic survey: Knekt and colleagues at the Finnish Institute for Health and Welfare followed 13,994 men and women aged 30 to 69 for 39 years, during which 1,805 were diagnosed with dementia. People who took a sauna 9 to 12 times a month had a hazard ratio of 0.47 in the first 20 years of follow-up, compared with those who went less than four times a month or never. Over the whole 39 years the hazard ratio was 0.81, a much weaker association.

A "hazard ratio" compares the rate of new diagnoses in two groups over time. A value of 0.34 means the frequent sauna users were diagnosed at about a third of the rate of the comparison group, after statistical adjustment. Hazard ratios for dementia cannot be converted into IQ points, and neither study gave participants an IQ test. The question they answer is whether a brain disease was diagnosed, which is different from whether healthy people think better.

The same KIHD men also feature in an earlier paper in JAMA Internal Medicine, where frequent sauna use was linked to lower cardiovascular and all-cause mortality. That paper shows how lopsided the groups were: 601 men reported one session a week, 1,513 reported two to three, and only 201 reported four to seven. The striking dementia result rests on that small top group.

Observational studies can show that two things go together. They cannot easily show why. Several features of the sauna studies call for caution.

• Healthy users: People who are well enough and have the time to use a sauna most days may differ from others in health, fitness and lifestyle. The KIHD dementia analysis adjusted for age, alcohol use, body mass index, blood pressure, smoking, type 2 diabetes, previous heart attack, resting heart rate and LDL cholesterol. It did not list education, income or physical activity among its adjustments, and education in particular is a strong predictor of dementia risk.

• Reverse causation: Dementia develops slowly. People in the early, undiagnosed stages, or with heart and other conditions that also raise dementia risk, may already be cutting back on sauna visits. In the Mobile Clinic data the association was strongest in the first 20 years and weaker over the full follow-up, which fits several explanations, including this one.

• A single measurement: In both cohorts, sauna use was reported once, at the start, by questionnaire. Habits can change over two or three decades.

• One country, one habit: The KIHD study enrolled only men from eastern Finland. Finnish sauna culture, with regular sessions at high heat, may not translate to infrared cabins or occasional gym saunas elsewhere.

Our page on whether IQ is correlated with dementia explains how childhood ability and education shape later dementia risk, one reason confounding is hard to rule out in studies like these. No randomized trial has assigned people to frequent sauna use and tracked dementia or cognitive scores.

Heat stress, when the body cannot shed heat fast enough, has been studied for decades in soldiers, workers and athletes. Hancock and Vasmatzidis concluded that its effects depend on the kind of task and track the rise in deep body temperature. A later meta-analysis by Hancock, Ross and Szalma pooled 528 effect sizes from 49 publications and found a substantial overall drop in performance under heat and cold. Cognitive tasks were the least affected, while perceptual and psychomotor tasks suffered more.

Experiments with saunas themselves are few and small.

• After a session: Cernych and colleagues gave 16 young men a Finnish sauna session that raised their rectal temperature from about 37.1°C to 38.8°C. Ninety minutes later, once their temperature had returned to baseline, their brain-wave recordings had changed, but their performance on two attention tasks had not.

• Memory consolidation: In a pilot study of 70 young adults and a pre-registered replication with 60 more, Cudeiro and colleagues showed participants a set of pictures, gave some of them a 7-minute sauna session at 50°C the next day, and tested recognition a day later. People who had the hot session recognized fewer pictures than controls who had no heat or a 28°C session. This suggests heat can disrupt memory for recently learned material, which runs against the idea of a quick brain boost.

Sweating in a sauna also costs body water. Wittbrodt and Millard-Stafford pooled 33 studies of dehydration and found a small overall impairment in cognitive performance (effect size -0.21), which was larger when people had lost more than 2% of their body mass. On a 15-point scale, -0.21 corresponds to about 3 points on the tasks tested, mostly attention, executive function and motor coordination, not IQ.

Articles promoting sauna for the brain usually mention two mechanisms. The first is "BDNF" (brain-derived neurotrophic factor), a protein that supports the growth and survival of nerve cells. In a randomized crossover trial, Glazachev and colleagues gave 20 healthy young men ten sessions of whole-body heating over two weeks and found that blood levels of BDNF rose more than after sham sessions. That trial did not measure cognition, and blood BDNF is an indirect marker of what happens in the brain.

The second is "heat shock proteins", molecules that help cells refold or clear damaged proteins. Hunt and colleagues, in a narrative review, noted that heat therapy raises heat shock protein levels in healthy people and argued that this could in principle protect against the protein build-up seen in Alzheimer's and Parkinson's disease. They described the research in patients as limited and called for trials.

A third possibility is simply cardiovascular. The Finnish group's review in Mayo Clinic Proceedings proposes that regular sauna use may lower blood pressure and improve blood-vessel function, which could in turn matter for the ageing brain. Physical exercise has a much larger evidence base on this point, covered in our page on whether exercise can affect your IQ score. Claims about heat and the brain resemble claims about supplements such as ashwagandha: plausible biology, small human studies, and no test of intelligence itself.

For most healthy adults, sauna bathing is well tolerated. Hannuksela and Ellahham's review lists unstable angina, a recent heart attack and severe aortic stenosis as contraindications, and warns that drinking alcohol in the sauna raises the risk of low blood pressure, abnormal heart rhythms and sudden death. In a study of deaths in Finnish saunas between 1990 and 2002, Kenttämies and Karkola found fewer than 2 deaths per 100,000 inhabitants per year, and half of the people who died were under the influence of alcohol. Anyone with a heart condition, low blood pressure or another medical concern should talk to their doctor before using a sauna regularly.

Finnish cohort studies link frequent sauna use with a lower risk of dementia, but they are observational and cannot prove cause and effect. No randomized trial has tested sauna against dementia or cognitive decline.

There is no evidence that it does. No study has measured IQ before and after regular sauna use, and short-term experiments show no gain in test performance.

Yes. Heat stress lowers performance on many tasks, though cognitive tasks are affected less than perceptual and motor ones, and dehydration adds a small further impairment.

One small trial in 20 young men found higher blood BDNF after ten heating sessions. It did not test thinking, and blood levels are only an indirect guide to the brain.

Most went two to three times a week. Only 201 of 2,315 men went four to seven times a week, the group with the lowest dementia risk.

Regular sauna use is linked to lower dementia risk in Finnish men and women, and there are plausible biological reasons it might help the heart and brain. The link has not been tested in a randomized trial, the comparison groups may differ in ways the studies could not adjust for, and no study suggests sauna raises intelligence. In the short term, heat and dehydration tend to make test performance slightly worse. If you want a clear measure of your reasoning ability, try a professionally developed IQ test.

1. Laukkanen, T., Kunutsor, S., Kauhanen, J., & Laukkanen, J. A. (2017). Sauna bathing is inversely associated with dementia and Alzheimer's disease in middle-aged Finnish men. Age and Ageing, 46(2), 245-249. [doi.org/10.1093/ageing/afw212](. doi.org

2. Knekt, P., Järvinen, R., Rissanen, H., Heliövaara, M., & Aromaa, A. (2020). Does sauna bathing protect against dementia? Preventive Medicine Reports, 20, 101221. [doi.org/10.1016/j.pmedr.2020.101221](. doi.org

3. Laukkanen, T., Khan, H., Zaccardi, F., & Laukkanen, J. A. (2015). Association between sauna bathing and fatal cardiovascular and all-cause mortality events. JAMA Internal Medicine, 175(4), 542-548. [doi.org/10.1001/jamainternmed.2014.8187](. doi.org

4. Hancock, P. A., & Vasmatzidis, I. (2003). Effects of heat stress on cognitive performance: The current state of knowledge. International Journal of Hyperthermia, 19(3), 355-372. [doi.org/10.1080/0265673021000054630](. doi.org

5. Hancock, P. A., Ross, J. M., & Szalma, J. L. (2007). A meta-analysis of performance response under thermal stressors. Human Factors, 49(5), 851-877. [doi.org/10.1518/001872007X230226](. doi.org

6. Cernych, M., Satas, A., & Brazaitis, M. (2018). Post-sauna recovery enhances brain neural network relaxation and improves cognitive economy in oddball tasks. International Journal of Hyperthermia, 35(1), 375-382. [doi.org/10.1080/02656736.2018.1504992](. doi.org

7. Cudeiro, J., Soto, D., & Gutiérrez, E. (2023). Heat exposure following encoding can interfere with subsequent recognition memory. Scientific Reports, 13, 11024. [doi.org/10.1038/s41598-023-38248-w](. doi.org

8. Wittbrodt, M. T., & Millard-Stafford, M. (2018). Dehydration impairs cognitive performance: A meta-analysis. Medicine & Science in Sports & Exercise, 50(11), 2360-2368. [doi.org/10.1249/MSS.0000000000001682](. doi.org

9. Glazachev, O. S., Zapara, M. A., Kryzhanovskaya, S. Y., Dudnik, E. N., Yumatov, E. A., & Susta, D. (2021). Whole-body repeated hyperthermia increases irisin and brain-derived neurotrophic factor: A randomized controlled trial. Journal of Thermal Biology, 101, 103067. [doi.org/10.1016/j.jtherbio.2021.103067](. doi.org

10. Hunt, A. P., Minett, G. M., Gibson, O. R., Kerr, G. K., & Stewart, I. B. (2020). Could heat therapy be an effective treatment for Alzheimer's and Parkinson's diseases? A narrative review. Frontiers in Physiology, 10, 1556. [doi.org/10.3389/fphys.2019.01556](. doi.org

11. Laukkanen, J. A., Laukkanen, T., & Kunutsor, S. K. (2018). Cardiovascular and other health benefits of sauna bathing: A review of the evidence. Mayo Clinic Proceedings, 93(8), 1111-1121. [doi.org/10.1016/j.mayocp.2018.04.008](. doi.org

12. Hannuksela, M. L., & Ellahham, S. (2001). Benefits and risks of sauna bathing. American Journal of Medicine, 110(2), 118-126. [doi.org/10.1016/S0002-9343(00)00671-9](. doi.org

13. Kenttämies, A., & Karkola, K. (2008). Death in sauna. Journal of Forensic Sciences, 53(3), 724-729. [doi.org/10.1111/j.1556-4029.2008.00703.x](. doi.org

Hero image: Heating chimneyless sauna 01, by Periegetes, CC BY-SA 4.0. Via Wikimedia Commons.