Insufficient evidence / under studyB/CgradePlausibility · Plausible / established mechanism (thermoregulatory); outcome evidence observationalThermal / Thermoregulatory
Dry hot air at roughly 71–100 °C — and the row where the strongest evidence in the whole thermal area attaches: the Kuopio Ischaemic Heart Disease cohort. The association is large and consistent but observational, male-only and single-population, which is exactly why it is B/C and not higher.
Origin & lineage
Traditional dry hot-air sauna (~71–100 °C, convective).
Claimed mechanism
Convective whole-body heating provoking a thermoregulatory and cardiovascular response (vasomotor load, heat-shock protein induction).
Plausibility
Plausible / established mechanism (thermoregulatory); outcome evidence observational.
Evidence — grade B/C
Anchor cohort: Laukkanen T. et al., JAMA Internal Medicine 2015;175(4):542–548 (PMID 25705824) — Kuopio Ischaemic Heart Disease cohort, ~2,315 middle-aged Finnish men, ~20-year follow-up, higher session frequency associated with substantially lower cardiovascular mortality; observational, male-only, single population. Wider review: Kunutsor, Jae & Laukkanen, Mayo Clinic Proceedings 2023. Calibration anchor: sits alongside Whole-Body Vibration (also B/C) — comparable observational weight.
Market
Makers: Traditional and commercial sauna builders. Models: Wood/electric dry saunas. Price: Varies widely.
Kernel — keep vs set aside
Keep — real substrate
A real, dosable thermal stimulus with a coherent mechanism and the strongest observational outcome signal in this family.
Set aside — claim
The evidence is observational and single-population — association, not proven causation; the KIHD result belongs here and must not be migrated onto the infrared row.
Regulatory status by jurisdiction
Registration or clearance is a market-access fact, never proof of efficacy.