Twenty years. Nearly two thousand Finnish men. And a finding so clean it almost doesn't feel like science — it feels like confirmation of something we already knew in our bones. Dr. Jari Laukkanen's JAMA study is not a pilot. It is not preliminary. It is one of the most robust longitudinal datasets on heat exposure ever assembled, and the conclusion is unambiguous: the more you sauna, the less likely you are to die from cardiovascular causes. Four to seven times per week yields a 50% reduction. That number does not move much even after you adjust for smoking, alcohol, obesity, cholesterol, physical activity, and socioeconomic status. Sauna use is doing something independent of everything else.
The knowledge base corroborates this from multiple directions. Our academic paper on sauna and neurocognitive disease finds a 65% reduced risk of Alzheimer's and a 66% lower risk of dementia in frequent users — numbers that dwarf most pharmaceutical interventions for cognitive decline. The mechanism connecting heart and brain is the same: improved vascular function, lower systemic inflammation, and the continuous activation of heat shock proteins that prevent misfolded protein aggregation. What Laukkanen's cardiovascular data and the dementia research share is a dose-response curve. More sessions, longer duration, more benefit. There is no ceiling visible in the data yet.
Where the researchers currently agree: sauna mimics moderate cardiovascular exercise at the physiological level. Heart rate climbs to 120–150 beats per minute. Plasma volume expands. Vascular compliance improves. You are training your circulatory system without cortisol spikes or joint load. Where there is still genuine uncertainty: the dementia mechanisms. Laukkanen himself says he wants to investigate those pathways more deeply. The heat shock protein hypothesis is compelling but not yet proven causally in humans.
Laukkanen's protocol is 79 degrees Celsius — that is roughly 174 degrees Fahrenheit — for sessions of at least 20 minutes. The risk reduction is visible at two to three sessions per week and substantially amplified at four to seven. If you can only manage two sessions per week right now, start there. Consistency over intensity. A sustainable four-times-per-week habit built over months will outperform heroic daily sessions that burn you out by week three.
Here is what surprises me most when I look across everything in this knowledge base: the Finnish populations in these studies are not doing anything exotic. They are not biohacking. They are not optimizing. They are following a cultural ritual that their grandparents followed, in a wooden room, sweating quietly. The data is extraordinary precisely because the practice is ordinary. That is the lesson. The most powerful health interventions are often the ones embedded so deeply in daily life that you stop thinking of them as interventions at all.