Sauna use may reduce dementia and Alzheimer's risk. Since the data has made this case, the question is why? There may be a few mechanisms at play: • Sauna use improves vascular health and blood pressure - both interventional and observational studies support this. • Heat shock proteins produced in response to heat stress may prevent the damaging neurodegenerative effects of protein aggregation. Poor vascular health plays a role in breakdown of the blood-brain barrier - one of the earliest signs of dementia. Improving and sustaining vascular health may be immensely important for protecting cognition. Sauna use strongly activates heat shock proteins. For instance, spending 30 minutes at 163°F can boost their levels by 50% from the baseline. These heat shock proteins help prevent protein aggregation in the brain, a factor linked to neuroinflammation and Alzheimer's disease. The caveat is that observational data is at play here. We probably won't see a randomized controlled trial studying the effects of sauna use on dementia risk spanning several decades. Thus, the best evidence we have for saunas in this respect comes from a combination of observational data and studies examining biomarkers associated with dementia. While we still can't say definitively this isn't healthy user bias in some form, the variety of mechanisms at play at the least make a case for that being relatively unlikely and generally support sauna more broadly as at the least a healthy lifestyle habit. If you don't have access to a sauna, you can still enjoy the benefits of a heat shock response through a hot bath. 104ºF for at least 20 minutes seems to be a good threshold for inducing the expression of heat shock proteins. Discussion of hot bath vs. sauna: youtube.com/watch?v=RWkv9ad7… Broad overview on sauna available here: foundmyfitness.com/topics/sa…