Proof Engine Verification: Frequent sauna use 4 to 7 times per week dramatically lowers risk of heart disease, dementia, and all-cause mortality.

Verdict: PARTIALLY VERIFIED - **Heart disease (SC1 — HOLDS):** Three independent peer-reviewed sources confirm the association. Laukkanen et al. 2015 (*JAMA Internal Medicine*) found sudden cardiac death hazard ratio (HR) 0.37 (95% CI 0.18–0.75) for 4–7 sauna sessions/week vs 1/week — a 63% reduction. Laukkanen et al. 2018 (*BMC Medicine*) found fatal CVD HR 0.30 (95% CI 0.14–0.64) — a 70% reduction. A 2018 Mayo Clinic Proceedings systematic review independently confirms the cardiovascular benefit. - **Dementia (SC2 — HOLD