Preface

The strongest evidence supports regular Finnish (dry) sauna bathing as an adjunctive cardiovascular and all‑cause mortality risk‑reduction habit, based on large prospective cohort data (moderate certainty).[1][2] Evidence for deliberate cold exposure (cold‑water immersion, whole‑body cryotherapy) is substantially weaker; small, short‑term trials with surrogate endpoints and no mortality or hard‑outcome data (low to very‑low certainty).[3][4] Both interventions carry real cardiovascular risk in susceptible individuals, and neither is “guideline‑recommended” therapy for longevity; both should be positioned as adjunctive lifestyle measures with informed consent, and cold exposure in particular remains largely experimental.[5][6]



1. Scope

Full title: Clinical Knowledge Summary: Sauna and cold exposure protocols (Longevity Medicine).

Covered:

– Finnish/dry sauna bathing; brief mention of infrared and steam variants.

– Deliberate cold exposure: cold‑water immersion (CWI), cold showers, whole‑body cryotherapy (WBC).

– Adult ambulatory patients attending a private longevity clinic, as an adjunct to (not a replacement for) conventional primary/secondary care.

Not covered:

– Occupational/environmental heat–cold exposure and climate‑related morbidity (referenced only for mechanism/safety).[5][6]

– Therapeutic hyperthermia for oncology, neonatal cooling, or targeted temperature management post‑arrest.

– Contrast hydrotherapy for acute sports recovery as a performance (rather than longevity) endpoint.

– Paediatric populations.

All recommendations are for adjunctive lifestyle care. Where an intervention is not supported by high‑quality outcome data this is flagged explicitly as off‑label/experimental/expert‑consensus/mechanistic only.



2. Background and pathophysiology

Biological rationale (heat):

– Passive heat stress raises heart rate to 100–150 bpm and increases cardiac output, functionally resembling low‑to‑moderate aerobic exercise.[1]

– Proposed longevity‑relevant mechanisms with human supporting data: improved endothelium‑dependent vasodilatation, reduced arterial stiffness, lower systemic blood pressure, favourable autonomic modulation (increased heart‑rate variability), and reduced systemic inflammation.[2][7]

– Heat‑shock protein induction and hormetic stress adaptation are biologically plausible contributors but the direct human causal linkage to ageing outcomes is not established (mechanistic plausibility only).[2]

Biological rationale (cold):

– Acute cold triggers sympathetic activation, catecholamine and endorphin release, peripheral vasoconstriction, and increased afterload.[5][6]

– Repeated cold exposure activates brown adipose tissue and increases energy expenditure, with plausible effects on cardiometabolic risk factors — but derived from small mechanistic studies.[4][8]

– Effects on inflammation are inconsistent and time‑dependent: acute rises in inflammatory markers immediately post‑immersion, with possible delayed reductions.[3]

Preclinical / lower‑certainty subsection (clearly separated — not a basis for clinical recommendation):

– Hibernating mammals and model organisms suggest associations between lower body/environmental temperature and longevity.[8]

– WBC has been reported to raise blood sirtuin (SIRT1/SIRT3) concentrations and antioxidant capacity in small human studies — these are surrogate biomarkers with no demonstrated link to clinical ageing outcomes.[9]

– Do not infer healthspan or lifespan benefit from any of these surrogate/preclinical signals.



3. Evidence base and grading

Overview of available clinical evidence:

– Sauna: large long‑term prospective cohort (KIHD, n≈2,315 middle‑aged Finnish men, median 20.7 y); supportive smaller interventional/RCT data on blood pressure, endothelial and arterial function; comprehensive narrative and semi‑systematic reviews.[1][10][2][7][11]

– Cold exposure: systematic review/meta‑analysis of CWI (11 studies, n≈3,177); scoping/interventional review for healthy ageing; small pilot/exploratory WBC trials with surrogate endpoints.[3][4][9][12]

– Key outcomes studied: all‑cause and cardiovascular mortality (sauna, cohort only); blood pressure, endothelial function, arterial stiffness (surrogates); inflammatory markers, mood/perceived stress, sleep, sickness absence (cold); body composition and immune parameters (cold, pilot).

GRADE‑style certainty and strength of recommendation by outcome:

Intervention / Outcome	Evidence statement	Certainty	Key downgrades	Recommendation
Sauna — CV & all‑cause mortality	Large prospective cohort: 4–7 sessions/week vs 1/week associated with lower all‑cause mortality (HR 0.60) and SCD (HR 0.37) [1], [10]	Moderate	Indirectness (single population, middle‑aged Finnish men, no women; observational — no RCT for hard endpoints); residual confounding	Conditional — offer as adjunctive habit in suitable patients
Sauna — BP / endothelial function / arterial stiffness	Small RCTs/interventional studies show BP reduction and improved vascular function [2], [7]	Low–Moderate	Small samples, short duration, surrogate endpoints	Conditional
Sauna — dementia / Alzheimer’s	Cohort association (up to 65% lower risk at high frequency) [2], [13]	Low	Single cohort, observational, confounding	Only as hypothesis‑generating — do not offer for this indication
Cold — cardiometabolic risk factors / BAT / metabolism	Small interventional studies suggest favourable effects [4], [8]	Very low	Small n, surrogate endpoints, heterogeneity, no hard outcomes	Only in research / conditional adjunct with consent
Cold — stress / mood / wellbeing / sleep	Meta‑analysis: reduced stress at 12 h; improved sleep/QoL; 29% lower sickness absence (narrative) [3]	Low	Heterogeneity, few studies per outcome, imprecision	Conditional
Cold — inflammation / immune modulation	Mixed; acute rise then possible delayed fall; inconsistent [3]	Very low	Inconsistency, protocol heterogeneity	Recommend against relying on for anti‑inflammatory benefit
WBC — ageing biomarkers (sirtuins, antioxidants)	Small studies show surrogate changes [9], [12]	Very low	Tiny n, no control/hard outcomes, publication bias likely	Only in research
Cold/heat — hard CV outcomes in at‑risk groups	Extreme temperature associated with increased MI, arrhythmia, HF, SCD [5], [6]	Moderate (harm)	—	Caution / recommend against in high‑risk groups

Publication bias: likely for cold/WBC (small positive exploratory studies, commercial interest). Sauna cohort evidence is robust but geographically narrow — external validity to UK, women, and non‑habituated users is uncertain.[10]



4. Patient selection and indications

Who might benefit (sauna — best‑supported):

– Middle‑aged adults with elevated cardiometabolic risk (hypertension, dyslipidaemia, sedentary phenotype) seeking an adjunctive, exercise‑adjacent habit.[1][2]

– Adults who tolerate and enjoy heat exposure and can achieve regular frequency (evidence strongest at ≥2–3, ideally 4–7 sessions/week).[1]

– Those wanting an adjunct alongside — not instead of — physical activity; benefits may be additive to fitness and other lifestyle factors.[11]

Who might be considered (cold — weaker evidence, individualised):

– Generally healthy adults seeking wellbeing, stress, or sleep benefits, accepting that evidence is low‑certainty.[3][4]

– Athletic individuals: note the distinction between performance/recovery goals and longevity goals — cold immersion may blunt some training adaptations, and longevity benefit is unproven.

Exclusion / high‑risk groups (both):

– Unstable/severe cardiovascular disease: recent MI or ACS, unstable angina, severe/symptomatic aortic stenosis, decompensated heart failure, uncontrolled arrhythmia, uncontrolled hypertension.[5][6]

– Cold specifically raises afterload, BP, blood viscosity and can trigger vasospasm, arrhythmia and HF decompensation — avoid in those with reduced cardiac reserve or coronary disease.[5][6]

– Pregnancy (heat): avoid deliberate hyperthermia; expert‑consensus caution.

– Orthostatic hypotension, autonomic dysfunction, poorly controlled diabetes with autonomic/thermoregulatory impairment.[5]

– Cold urticaria, Raynaud’s/cryoglobulinaemia (cold); active infection/febrile illness.

– Alcohol intoxication (major cause of sauna‑related death) — absolute avoidance during use.

Regulatory / ethical status:

– Sauna and cold exposure are lifestyle activities, not licensed medical therapies; use for “longevity” or disease prevention is off‑label/non‑guideline. WBC devices are not approved for anti‑ageing indications.

– Sauna for cardiometabolic risk reduction: reasonable as adjunctive care with informed consent (conditional).

– Cold exposure and WBC for longevity endpoints: best framed as experimental — ideally within research/registry frameworks, and otherwise only as adjunctive care with explicit informed consent about the low certainty of benefit and real risks.



5. Assessment and baseline work‑up

Pre‑intervention assessment:

– History: cardiovascular symptoms (chest pain, dyspnoea, syncope, palpitations), known CVD/arrhythmia, hypertension control, diabetes and complications, pregnancy status, medications affecting thermoregulation/volume (diuretics, antihypertensives, anticholinergics, vasodilators), alcohol use, cold‑related disorders (Raynaud’s, cold urticaria).[5]

– Examination: resting BP and heart rate, cardiovascular and volume status; consider orthostatic BP.

– Risk scoring: formal cardiovascular risk assessment (e.g. QRISK3 in UK practice) to contextualise adjunctive prevention.

– Baseline investigations (tailored, not mandatory for low‑risk patients): resting ECG in those with cardiac risk factors or planned intense protocols; consider exercise tolerance assessment/cardiology input before initiating in patients with known or suspected CVD.[5][6]

– Optional longevity biomarkers for tracking (interpret cautiously as surrogates only): office/ambulatory BP, lipids, HbA1c, hsCRP, resting heart rate/HRV. Do not present biomarker change as proof of hard clinical benefit.

Risk stratification:

– Low risk: younger, no CVD, controlled risk factors, heat/cold‑tolerant → standard protocols.

– Moderate risk: controlled hypertension, stable CVD risk factors, older age → conservative titration, medical oversight, avoid extremes.

– High risk: established/unstable CVD, arrhythmia, autonomic dysfunction, pregnancy → avoid or specialist input only.[5][6]

Baseline documentation:

– Indication and shared‑decision‑making/consent record (off‑label status noted); baseline BP/HR, medications, chosen protocol parameters, and the biomarkers being followed to allow meaningful longitudinal comparison.



6. Dosing regimens and practical implementation

Sauna — regimen with the best human support (extrapolated from KIHD cohort exposure; note cohort ≠ prescriptive RCT dose):[1][2]

– Modality: traditional Finnish dry sauna, ~80–100°C, low humidity.

– Duration: ~5–20 min per session; cohort benefit was greater with sessions >19 min, but longer sessions increase orthostatic/dehydration risk — titrate individually.

– Frequency: dose–response observed; ≥2–3 sessions/week, up to 4–7/week associated with greatest risk reduction.[1]

– Hydration before and after; avoid alcohol; cool‑down gradually; rise slowly to prevent orthostatic syncope.

– Infrared saunas operate at lower temperatures (~45–60°C); outcome evidence is weaker and should not be assumed equivalent to Finnish sauna data (indirect/limited evidence).

Cold exposure — protocols (low‑certainty; parameters not standardised):[3][4]

– Cold‑water immersion: ~10–15°C; short durations (commonly ≤5 min; some protocols to ~10 min). Shorter exposures/lower temperatures may suffice for reported effects; longer/colder exposures increase cold‑shock and cardiac risk.[4][3]

– Cold showers: a lower‑risk entry point; associated with reduced sickness absence in one study.[3]

– Whole‑body cryotherapy: −110 to −140°C for 2–3 min (or ~−90°C) in commercial units; longevity benefit unproven — experimental/only in research.[9][14][12]

– Always avoid unsupervised open‑water/cold‑shock exposure; enter gradually; never alone; never after alcohol.

Contrast (sauna followed by cold plunge): traditional and popular, but the combined protocol is poorly studied and the additive health effect is unproven — mechanistic plausibility only; the cold component adds cardiovascular strain.[7]

Distinguishing evidence tiers:

– Robust human data: regular Finnish sauna for CV/mortality risk association.[1][2]

– Caution / early‑phase or preclinical: all cold and WBC longevity claims, infrared sauna equivalence, contrast therapy, and any biomarker‑based (“sirtuin”, “HSP”) justification.[3][9]



7. Monitoring, safety and follow‑up

Monitoring plan:

– Clinical: tolerance, symptoms during/after (dizziness, chest pain, palpitations, syncope, excessive fatigue), hydration, adherence.

– Physiological: periodic resting BP and heart rate; reassess in patients on antihypertensives/diuretics as heat can potentiate hypotension and volume depletion.[5][6]

– Biomarkers (optional, interpret as surrogates): BP trend, resting HR/HRV, hsCRP, HbA1c, lipids — track for direction of travel, not as proof of longevity benefit.

Timepoints (pragmatic, expert‑consensus):

– Short term (2–4 weeks): tolerance and symptom review after initiation/titration.

– Medium term (3 months): BP/medication review, adherence, surrogate biomarkers.

– Long term (6–12 months): reassess cardiovascular risk, continued suitability.

Adverse effects:

– Common: transient orthostatic hypotension, light‑headedness, dehydration, heat discomfort (sauna); cold‑shock response, transient BP surge, discomfort, numbness (cold).[3][5][6]

– Serious/rare: syncope with injury, arrhythmia, myocardial ischaemia/infarction, HF decompensation, sudden cardiac death — risk concentrated in those with CVD, older adults, and with alcohol or excessive exposure. Cold‑water immersion carries risk of cold‑shock‑induced arrhythmia and drowning.[5][6]

– Required actions: stop for chest pain, syncope, significant arrhythmia symptoms, or presyncope; reduce duration/frequency for orthostatic symptoms; review/adjust antihypertensives and diuretics; refer to cardiology for any ischaemic or arrhythmic event.

Interactions:

– Diuretics/antihypertensives + heat → additive hypotension/volume depletion; anticholinergics impair sweating/thermoregulation; beta‑blockers blunt heart‑rate response.[5]

– Alcohol and sedatives markedly increase risk (impaired thermoregulation, arrhythmia, drowning) — contraindicated with use.

– Cold + established CVD → additive afterload/ischaemic risk.[5][6]

Special populations:

– Pregnancy: avoid deliberate hyperthermia (heat); cold exposure not adequately studied — avoid extremes (expert‑consensus caution).

– Frailty/older adults: impaired thermoregulation and reduced cardiac/vascular reserve raise risk — conservative parameters and closer oversight.[5]

– Renal/hepatic impairment: caution with fluid/electrolyte shifts and drug handling; individualise.

– Extremes of age: not recommended in children (out of scope).



8. Contraindications and cautions

Absolute contraindications:

– Recent MI/ACS, unstable angina, decompensated heart failure, severe symptomatic aortic stenosis, uncontrolled or life‑threatening arrhythmia.[5][6]

– Acute febrile illness; alcohol intoxication during use.

– Cold‑specific: cold urticaria, cryoglobulinaemia, symptomatic Raynaud’s for direct cold immersion.

Relative contraindications / specialist advice required:

– Controlled but significant CVD, prior stroke/TIA, uncontrolled hypertension, orthostatic hypotension, autonomic dysfunction, poorly controlled diabetes with complications, pregnancy, significant frailty, and use of thermoregulation‑affecting medications.[5][6]

Situations where harm likely outweighs benefit (current evidence):

– Deliberate cold exposure or WBC in patients with established coronary disease, arrhythmia, or reduced cardiac reserve — cold predictably raises BP, afterload and ischaemic/arrhythmic risk with no proven longevity benefit.[5][6]

– Any protocol pursued instead of evidence‑based cardiovascular prevention.



9. Practical management scenarios

Scenario A — Middle‑aged adult with multiple cardiometabolic risk factors (hypertension, dyslipidaemia, sedentary):

– Recommendation: Offer regular Finnish sauna as an adjunct — conditional recommendation, moderate certainty.[1][2]

– Assessment: cardiovascular risk (QRISK3), BP control, medication review (diuretics/antihypertensives), resting ECG if additional cardiac risk.

– Shared decision‑making: explain it is adjunctive to, not a substitute for, exercise, diet and guideline pharmacotherapy; off‑label preventive use; observational basis.

– Initiation: start ~2–3 sessions/week, ~10–15 min at ~80–90°C; hydrate; no alcohol; gradual cool‑down; build toward higher frequency as tolerated.[1]

– Monitoring: symptom/tolerance review at 2–4 weeks; BP and medication review at 3 months.

– Escalate/stop: chest pain, syncope, palpitations, or symptomatic hypotension → stop and reassess/refer.

Scenario B — Older, frail patient with multimorbidity:

– Recommendation: Restrict / avoid most protocols; if used, only low‑intensity heat with oversight — conditional against; recommend against deliberate cold/WBC.[5][6]

– Assessment: cardiac reserve, orthostatic BP, autonomic function, falls risk, medications; cardiology input if any CVD.

– Shared decision‑making: emphasise heightened thermoregulatory and cardiovascular vulnerability and unproven benefit in this group.

– Initiation (if proceeding with heat only): shorter, cooler, less frequent sessions; supervised; never alone; strict hydration.

– Monitoring: close symptom and BP review; low threshold to stop.

– Escalate/stop: any presyncope, ischaemic symptoms, arrhythmia, or dehydration → discontinue and refer.

Scenario C — Adjunct in a patient already under specialist care (e.g. stable treated CVD or metabolic disease):

– Recommendation: Consider only after specialist liaison; sauna conditional, cold generally avoid — conditional.[5][6][2]

– Assessment: confirm disease stability with the treating specialist; review interacting medications.

– Shared decision‑making: coordinate with secondary care; document consent and off‑label status.

– Initiation: conservative sauna parameters if approved; avoid cold immersion given afterload/ischaemic risk.

– Monitoring: joint plan with specialist; BP and symptom tracking.

– Escalate/stop: any new cardiovascular symptoms → stop and return to specialist.

Scenario D — Generally healthy adult requesting cold exposure for wellbeing/stress:

– Recommendation: Consider low‑risk cold exposure (cold showers) with consent; frame benefits as low‑certainty — conditional, low certainty.[3][4]

– Assessment: screen for cardiac/cold contraindications; caution about cold‑shock and never immersing alone.

– Initiation: begin with brief cold showers; if progressing to immersion, ~10–15°C, ≤5 min, supervised, gradual entry.[4][3]

– Monitoring: tolerance, sleep/stress self‑report; reassess suitability periodically.

– Escalate/stop: chest pain, arrhythmia symptoms, or excessive cold‑shock response → stop and assess.



10. Research gaps and future directions

– No RCTs demonstrate that sauna or cold exposure reduces mortality or hard clinical events; sauna outcome data derive from a single, demographically narrow cohort (Finnish middle‑aged men). Generalisability to women, other ethnicities, and UK populations is unproven.[1][10]

– Optimal “dose” (temperature, duration, frequency), and whether infrared saunas confer equivalent benefit, are undefined.[2][7]

– Cold exposure evidence is dominated by small, heterogeneous, short‑term studies with surrogate endpoints; standardised protocols and adequately powered trials are needed.[3][4]

– WBC longevity claims rest on surrogate biomarkers (e.g. sirtuins, antioxidant capacity) with no demonstrated link to clinical ageing outcomes — remain experimental.[9][14][12]

– The combined sauna + cold (“contrast”) protocol popular in practice is essentially unstudied for health outcomes.[7]

– Priority questions: RCTs of sauna for cardiometabolic hard endpoints; dose‑finding and safety in at‑risk and older populations; head‑to‑head heat vs cold vs combined; effects in women and diverse populations; validated ageing‑biomarker endpoints linked to outcomes.

– Practice recommendation: cold exposure and WBC for longevity should ideally be pursued within well‑designed trials or clinical registries; sauna may be offered as adjunctive lifestyle care with appropriate patient selection and informed consent.

References

1. Association Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality Events. Laukkanen T, Khan H, Zaccardi F, Laukkanen JA. JAMA Internal Medicine. 2015;175(4):542-8. doi:10.1001/jamainternmed.2014.8187.
2. Cardiovascular and Other Health Benefits of Sauna Bathing: A Review of the Evidence. Laukkanen JA, Laukkanen T, Kunutsor SK. Mayo Clinic Proceedings. 2018;93(8):1111-1121. doi:10.1016/j.mayocp.2018.04.008.
3. Effects of cold-water immersion on health and wellbeing: A systematic review and meta-analysis. Cain T, Brinsley J, Bennett H, et al. PloS One. 2025;20(1):e0317615. doi:10.1371/journal.pone.0317615.
4. The Untapped Potential of Cold Water Therapy as Part of a Lifestyle Intervention for Promoting Healthy Aging. Kunutsor SK, Lehoczki A, Laukkanen JA. GeroScience. 2025;47(1):387-407. doi:10.1007/s11357-024-01295-w.
5. Nonoptimal Temperature and Cardiovascular Health: A Scientific Statement From the American Heart Association. Hanneman K, Alahmad B, Ghosh A, et al. Circulation. 2026;. doi:10.1161/CIR.0000000000001419.
6. Associations Between Extreme Temperatures and Cardiovascular Cause-Specific Mortality: Results from 27 Countries. Alahmad B, Khraishah H, Royé D, et al. Circulation. 2023;147(1):35-46. doi:10.1161/CIRCULATIONAHA.122.061832.
7. Effects of Heat and Cold on Health, With Special Reference to Finnish Sauna Bathing. Heinonen I, Laukkanen JA. American Journal of Physiology. Regulatory, Integrative and Comparative Physiology. 2018;314(5):R629-R638. doi:10.1152/ajpregu.00115.2017.
8. Cold and Longevity: Can Cold Exposure Counteract Aging?. Boulares A, Jdidi H, Douzi W. Life Sciences. 2025;364:123431. doi:10.1016/j.lfs.2025.123431.
9. The Effect of Repeated Whole-Body Cryotherapy on Sirt1 and Sirt3 Concentrations and Oxidative Status in Older and Young Men Performing Different Levels of Physical Activity. Wojciak G, Szymura J, Szygula Z, Gradek J, Wiecek M. Antioxidants (Basel, Switzerland). 2020;10(1):E37. doi:10.3390/antiox10010037.
10. Sauna bathing associated with reduced cardiovascular mortality. Lim GB. Nature Reviews. Cardiology. 2015;12(5):257. doi:10.1038/nrcardio.2015.35.
11. Does the Combination of Finnish Sauna Bathing and Other Lifestyle Factors Confer Additional Health Benefits? A Review of the Evidence. Kunutsor SK, Laukkanen JA. Mayo Clinic Proceedings. 2023;98(6):915-926. doi:10.1016/j.mayocp.2023.01.008.
12. Whole-Body Cryotherapy at -90 °C for 9 Weeks: Effects on Immune Function, Stress, and Immune-Related and Vascular Blood Parameters in Healthy Adults-Results of an Exploratory One-Armed Pilot Study. Aisenpreis PM, Aisenpreis S, Feisst M, Schleip R. Journal of Clinical Medicine. 2026;15(3):967. doi:10.3390/jcm15030967.
13. A study on neural changes induced by sauna bathing: Neural basis of the “totonou” state. Chang M, Ibaraki T, Naruse Y, Imamura Y. PloS One. 2023;18(11):e0294137. doi:10.1371/journal.pone.0294137.
14. Cold as a Therapeutic Frontier: Place of Whole-Body Cryotherapy in Modern Medicine. Dziugieł R, Bołtuć-Dziugieł K, Jaroszyński A. European Journal of Applied Physiology. 2026;126(5):2409-2417. doi:10.1007/s00421-026-06193-x.