Sauna and Heat Exposure: Strong Association, Weak Causal Proof

Summary

Regular sauna bathing shows a **large, steeply dose-responsive inverse association with cardiovascular and all-cause mortality** (roughly **HR 0.5–0.6 for 4–7 sessions/week vs 1/week** in Finnish men) — but that headline comes almost entirely from a single non-randomised cohort, and the RCT layer on the mechanisms it *should* work through (blood pressure, arterial stiffness, endothelial function) is largely **null**. Tier 2: a low-risk recovery and cardiovascular-hygiene practice worth doing, **not** the proven mortality-reducer the wellness industry sells. ---