What it is
Sauna bathing exposes the body to short bouts of dry or wet heat, raising heart rate and core temperature in a controlled, hormetic stress that resembles moderate exercise in some respects.
Why it matters for longevity
In a large Finnish cohort, more frequent sauna sessions were associated with substantially lower rates of fatal cardiovascular events and all-cause mortality, in a dose-dependent way. Plausible mechanisms include improved vascular function, lower blood pressure and heat-shock responses. Heat is often paired with cold and exercise for cardiovascular and VO2 max benefits.
What the evidence shows
The mortality data are striking but observational — people who sauna more may simply be healthier — so this is rated Emerging. Randomised evidence is mostly limited to short-term cardiovascular markers.
What to ask a clinic
Heat is a stressor: discuss suitability if you have cardiovascular disease, are pregnant or are dehydrated, and treat sauna as a complement to — not a replacement for — exercise.