Does regular sauna use protect your brain against decline?

Men who went to the sauna 4 to 7 times per week had, in a large Finnish cohort study (more than 2,300 participants, followed for an average of 21 years), a 66% lower risk of dementia and a 65% lower risk of Alzheimer's disease, compared with men who went only once a week. Those are strikingly large numbers. Yet a firm caveat applies: this is an observational association, not proof of cause and effect. People who visit the sauna frequently also tend to lead healthier lives in other respects.

Less frequent sauna use, two to three times per week, did not produce a statistically demonstrable reduction in risk in the same study. The effect therefore appears to emerge only at a high frequency, although that could also be a matter of insufficient statistical power in that middle group.

A broadly conducted review confirms the association with a lower risk of cognitive decline and cites improved blood vessel function as a possible explanation: more flexible arteries, lower blood pressure and better circulation are well-known risk factors for dementia. Whether that improvement in blood vessels actually protects the brain directly has not yet been demonstrated.

All available studies concern men in Finland, a population with a specific sauna culture. Whether women, or people in a different context, derive the same benefit is unknown on the basis of these data. There is no evidence of a direct effect on brain tissue; the biological explanation remains a hypothesis for the time being. A small study involving people who had been exposed to toxic substances showed cognitive improvement after a combination programme that included sauna, but in that study sauna was not the only factor and a control group was absent, so this says little about healthy people.