Sauna and Cardiovascular Health: 30 Years of Finnish Data

By Telos Wellness Editorial Team. Last reviewed 2026-05-12.

Saunas are associated with lower cardiovascular and all-cause mortality in the KIHD prospective cohort of 2,315 middle-aged Finnish men followed for a median 20.7 years (Laukkanen et al., JAMA Internal Medicine, 2015). The hazard ratio for all-cause mortality at 4–7 sessions per week was 0.60 (95% CI 0.46–0.78) compared with one session per week. The 2023 Kunutsor updated meta-analysis confirms the direction of effect. This article summarises the cardiovascular evidence and its limits.

The KIHD cohort — what it is and what it measures

The Kuopio Ischaemic Heart Disease Risk Factor Study (KIHD) is a prospective cohort of middle-aged Finnish men recruited in the late 1980s and followed for cardiovascular and total mortality outcomes for more than two decades. The cohort design and outcome ascertainment underlie the most-cited sauna-cardiovascular findings in the literature.

Cohort design, n and follow-up

KIHD recruited 2,682 men aged 42–60 in Kuopio, eastern Finland, between 1984 and 1989. Of these, 2,315 had complete baseline sauna data and entered the 2015 analysis (Laukkanen et al., JAMA Internal Medicine, 2015). Baseline assessment included physical examination, fasting blood draw, and a structured questionnaire on lifestyle factors including sauna frequency, session duration, and bath temperature. Median follow-up at the 2015 publication cut-off was 20.7 years.

Outcomes measured

The primary outcomes were all-cause mortality, fatal cardiovascular events (including fatal myocardial infarction and fatal stroke), and sudden cardiac death. Outcome data were drawn from Finnish national death registries and adjudicated against hospital records. All-cause mortality is defined as death from any cause across the follow-up window; cardiovascular mortality is death attributed to a cardiovascular cause; sudden cardiac death is death within 1 hour of symptom onset attributable to a cardiac cause.

Confounders adjusted

The KIHD multivariable Cox proportional hazards models adjusted for age, body mass index, smoking status, alcohol consumption, self-reported physical activity, socioeconomic status, prevalent cardiovascular disease, type 2 diabetes, total cholesterol, low-density lipoprotein cholesterol, and resting systolic blood pressure. Adjustment for physical activity is particularly relevant given that sauna and exercise share overlapping cardiovascular responses. Residual confounding cannot be excluded in any observational design.

All-cause and cardiovascular mortality results

A hazard ratio is a measure of the relative instantaneous risk of an outcome in one group compared with a reference group, conditional on survival to that time point. A hazard ratio of 0.60 indicates a 40% lower instantaneous risk; a hazard ratio of 1.00 indicates no difference. The 95% confidence interval (CI) is the range within which the true value lies with 95% probability.

Hazard ratios by sauna frequency

The KIHD cohort reports hazard ratios for sudden cardiac death of 0.78 (95% CI 0.63–0.97) at 2–3 sessions per week and 0.37 (0.18–0.75) at 4–7 sessions per week, compared with one session per week (Laukkanen et al., JAMA Intern Med, 2015 — S009). Cardiovascular mortality follows a similar dose-response pattern. The cohort is observational; the findings indicate an association, not a causal relationship in isolation.

Hazard ratios by session duration

Session duration was reported in three bands: 11 minutes or less, 11–19 minutes, and longer than 19 minutes. The strongest mortality association appeared in the longest duration band. Compared with sessions of 11 minutes or less, sessions longer than 19 minutes were associated with a hazard ratio of 0.48 (95% CI 0.31–0.75) for sudden cardiac death and 0.52 (0.34–0.79) for fatal cardiovascular events. The duration gradient is consistent across the frequency strata.

Hazard ratios by sauna temperature

Sauna temperature in the KIHD cohort was self-reported and clustered around the traditional Finnish operating range of 80–100°C. Within this range no clear temperature gradient on mortality emerged. The cohort does not include far-infrared or low-temperature electric cabins; the temperature findings are therefore confined to traditional Finnish stove and electric heater installations.

The dose-response chart

The table below summarises the KIHD dose-response data. The 4–7 sessions/week band shows the strongest association across all three primary cardiovascular outcomes, with the steepest gradient in sudden cardiac death.

Adapted from Laukkanen et al., JAMA Internal Medicine, 2015 (n=2,315 Finnish men aged 42–60, median follow-up 20.7 years) and Laukkanen et al., Age and Ageing, 2017 (dementia sub-analysis). The cohort is observational; residual confounding cannot be excluded.

Blood pressure — acute and longitudinal

The blood pressure literature on sauna is best read as two distinct questions: the within-session acute response and the change in resting blood pressure across weeks of regular use. The two are governed by different mechanisms.

Acute response: peripheral vasodilation

During a sauna session, cutaneous vasodilation reduces peripheral resistance, heart rate rises to 100–150 bpm, and diastolic blood pressure typically falls (Hussain & Cohen, 2018). Systolic blood pressure may rise modestly at session onset before falling as vasodilation completes. Cardiac output rises to support cutaneous blood flow. The acute response resembles light-to-moderate aerobic exercise in several physiological respects but without the muscular work component.

Longitudinal change in resting BP

Regular sauna bathing is associated with modest reductions in resting blood pressure. A 3-month far-infrared sauna trial reported a mean reduction of approximately 8 mmHg systolic and 6 mmHg diastolic, with wide confidence intervals (Beever, Can Fam Physician, 2009 — S002). The Hussain & Cohen 2018 systematic review (S001) describes the effect as biologically plausible and supported by acute and short-term data, with longer randomised trials required to confirm magnitude.

Infrared-specific data (Beever 2009)

Beever (2009) summarises a series of far-infrared cabin trials in cardiovascular risk-factor populations. Across three-month interventions, blood pressure reduction is the most consistent biomarker change, although trial sizes are small (typically 20–60 participants) and effect-size confidence intervals are wide. The infrared trials operate at ambient temperatures of 45–60°C with session durations of 30–45 minutes — a different exposure profile to the KIHD traditional-sauna data, but with overlapping core-temperature rise.

Endothelial function and Waon therapy

Endothelial function refers to the ability of vascular endothelium to regulate vascular tone, primarily through nitric oxide release. Flow-mediated dilation, measured by brachial-artery ultrasound, is the standard non-invasive index of endothelial function and a recognised cardiovascular risk marker.

Kihara 2002 — chronic heart failure cohort

Kihara et al. (J Am Coll Cardiol, 2002 — S005) reported improved flow-mediated dilation and cardiac function in 25 patients with chronic heart failure after two weeks of daily 60°C far-infrared sauna sessions (Waon therapy). Flow-mediated dilation is a brachial artery ultrasound measure of endothelial function. The trial is small and the cohort is patients in cardiac care; generalisation to a healthy population requires larger studies.

Waon therapy as developed by the Kagoshima University group is a 15-minute exposure at 60°C followed by 30 minutes of rest in a warm blanket. The protocol has been replicated in subsequent Japanese cardiac-rehabilitation trials with consistent direction on flow-mediated dilation and on B-type natriuretic peptide. The trial sizes remain small, and the cohorts are clinical rather than general population.

Flow-mediated dilation as the measured outcome

Flow-mediated dilation is assessed by measuring brachial artery diameter at baseline and again after a brief period of forearm ischaemia followed by reactive hyperaemia. The percent change in diameter is the FMD index. Improved FMD after repeated sauna exposure is interpreted as evidence of nitric oxide bioavailability and endothelial functional recovery, with mechanistic plausibility for the cohort findings on cardiovascular mortality.

Stroke and sudden cardiac death

Subsequent analyses of the KIHD cohort have reported a hazard ratio of approximately 0.39 (95% CI 0.18–0.83) for fatal and non-fatal stroke at 4–7 sauna sessions per week compared with one. Stroke is a smaller outcome category in the cohort than all-cause death and the confidence interval is correspondingly wider. The sudden cardiac death finding (HR 0.37 at 4–7 sessions/wk) is replicated in the 2015 analysis with consistent direction. The absolute event counts in the highest-frequency exposure groups are small, and the effect-size precision should be read in that context.

The Kunutsor 2023 updated meta-analysis

The 2023 systematic review and meta-analysis by Kunutsor and Laukkanen (Mayo Clin Proc Innov Qual Outcomes — S011) pools KIHD with subsequent cohort, trial and biomarker data published through 2022. Effect-size estimates for all-cause and cardiovascular mortality remain within the original 2015 confidence intervals. The update extends the evidence base in two directions: it adds a small number of replications from non-Finnish cohorts (which support the direction of effect with smaller magnitudes) and it confirms the biomarker findings on blood pressure and endothelial function. The update strengthens the case for a robust association without establishing causality.

Sauna as exercise mimetic — what overlaps and what does not

Sauna bathing and aerobic exercise share several physiological responses: heart rate rises to 100–150 bpm, peripheral resistance falls, and core temperature increases (Hussain & Cohen 2018 — S001). The KIHD cohort findings hold after adjustment for physical activity, suggesting the association with mortality is partially independent of exercise. Sauna is not a replacement for exercise; current NHS physical-activity guidance continues to apply independently of sauna use.

The shared responses include rise in cardiac output, reduction in systemic vascular resistance, modest increase in stroke volume, and induction of heat shock proteins. The responses that do not overlap include skeletal muscle contractile loading, glycogen depletion, mechanical bone loading, and the post-exercise insulin sensitivity window. A user replacing exercise with sauna would forgo the latter group; a user adding sauna alongside exercise gains the shared cardiovascular response on an additional weekly frequency.

Limitations of cohort evidence

The cardiovascular evidence base for sauna is strong by the standards of lifestyle epidemiology but rests largely on a single multi-decade cohort. Three specific limits are worth stating clearly.

Residual confounding

Multivariable adjustment in KIHD addressed the obvious confounders — age, BMI, smoking, alcohol, physical activity, socioeconomic status, prevalent disease — but cannot exclude unmeasured or imprecisely measured factors. A man using a sauna 4–7 times per week may differ from a man using it once per week in ways that the questionnaire did not capture (diet quality, sleep, social connection). Sensitivity analyses in the original paper and the 2023 update suggest residual confounding is unlikely to fully account for the effect, but cannot rule it out.

Cohort is Finnish men

The KIHD cohort comprises Finnish men aged 42–60 at baseline. Generalisation to women, to other ethnicities, to other age bands, and to populations with different baseline cardiovascular risk profiles is not directly supported by the cohort data. The 2023 Kunutsor update adds a small number of mixed-sex and non-Finnish replications, which support the direction of effect.

Reverse causation

Subclinical cardiovascular disease may reduce sauna attendance before clinical diagnosis, producing an apparent protective association. The original paper applied lag-period sensitivity analyses to mitigate this concern. The reverse-causation concern is more acute for the dementia sub-analysis (covered in the source article on sauna benefits) than for the cardiovascular outcomes.

Who should not sauna for cardiovascular reasons

The Hannuksela & Ellahham 2001 American Journal of Medicine review (S006) identifies absolute and relative cardiovascular contraindications. Absolute contraindications include unstable angina, recent myocardial infarction within 2 weeks, severe aortic stenosis, decompensated heart failure, and acute febrile illness. Relative contraindications include stable but uncontrolled hypertension, controlled arrhythmia, peripheral vascular disease, and severe varicose veins. Alcohol prior to or during a session is unsafe. A user with any cardiovascular condition should consult their GP or cardiologist before starting regular sauna bathing. The contraindication list is covered in full in the source article.

Summary

Headline figures from the KIHD cohort and 2023 Kunutsor update:

• All-cause mortality HR 0.60 (95% CI 0.46–0.78), 4–7 sessions/wk vs 1/wk (S009).
• Cardiovascular mortality HR 0.50 (0.31–0.81), same comparison (S009).
• Sudden cardiac death HR 0.37 (0.18–0.75), same comparison (S009).
• Strongest association at session duration above 19 minutes at 80–100°C traditional sauna.
• Blood pressure reduction of approximately -8/-6 mmHg in 3-month far-infrared trials (S002); biologically plausible, longer RCTs required.
• Improved flow-mediated dilation after 2 weeks of 60°C Waon therapy in chronic heart failure (n=25; S005).
• Direction of effect confirmed by the 2023 Kunutsor updated meta-analysis (S011).
• Cohort observational; residual confounding cannot be excluded; cohort is Finnish men aged 42–60.

For the broader evidence-grading context and the contraindication list see the source article on evidence-based sauna benefits. For the post-exercise protocol that draws on the same heat-shock-protein mechanism see sauna for muscle recovery.

Frequently asked questions

Are saunas good for your heart?

The KIHD cohort reports hazard ratios for sudden cardiac death of 0.78 (95% CI 0.63–0.97) at 2–3 sessions per week and 0.37 (0.18–0.75) at 4–7 sessions per week, compared with one session per week (Laukkanen et al., JAMA Intern Med, 2015 — S009). Cardiovascular mortality follows a similar dose-response pattern. The cohort is observational; the findings indicate an association, not a causal relationship in isolation.

Does sauna lower blood pressure?

Regular sauna bathing is associated with modest reductions in resting blood pressure. A 3-month far-infrared sauna trial reported a mean reduction of approximately 8 mmHg systolic and 6 mmHg diastolic, with wide confidence intervals (Beever, Can Fam Physician, 2009 — S002). The Hussain & Cohen 2018 systematic review (S001) describes the effect as biologically plausible and supported by acute and short-term data, with longer randomised trials required to confirm magnitude.

Does sauna improve cardiovascular function?

Kihara et al. (J Am Coll Cardiol, 2002 — S005) reported improved flow-mediated dilation and cardiac function in 25 patients with chronic heart failure after two weeks of daily 60°C far-infrared sauna sessions (Waon therapy). Flow-mediated dilation is a brachial artery ultrasound measure of endothelial function. The trial is small and the cohort is patients in cardiac care; generalisation to a healthy population requires larger studies.

Is sauna like exercise?

Sauna bathing and aerobic exercise share several physiological responses: heart rate rises to 100–150 bpm, peripheral resistance falls, and core temperature increases (Hussain & Cohen 2018 — S001). The KIHD cohort findings hold after adjustment for physical activity, suggesting the association with mortality is partially independent of exercise. Sauna is not a replacement for exercise; current NHS physical-activity guidance continues to apply independently of sauna use.

How many sessions per week are needed for cardiovascular benefit?

The strongest mortality association in the KIHD cohort appears at 4–7 sessions per week of at least 19 minutes duration, in a traditional sauna at 80–100°C (Laukkanen 2015 — S009). The 2023 Kunutsor meta-analysis (S011) is directionally consistent. Two to three sessions per week is associated with a smaller but still measurable reduction. Less than one session per week shows no association in the cohort data.

Can sauna replace cardio exercise?

The literature does not support sauna as a replacement for exercise. The KIHD cohort findings on mortality persist after adjustment for self-reported physical activity (S009), suggesting independent associations rather than substitution. Current NHS physical-activity guidance (150 minutes moderate intensity per week) continues to apply. Sauna is best framed as an adjunct to, not a substitute for, an active lifestyle.

Is sauna safe for someone with high blood pressure?

Stable, well-controlled hypertension is not an absolute contraindication, and short-term studies report acute and longitudinal reductions in resting blood pressure with regular use (S001, S002). Unstable angina, recent myocardial infarction (within 2 weeks), severe aortic stenosis, and decompensated heart failure are absolute contraindications (Hannuksela & Ellahham 2001 — S006). A user with cardiovascular disease should consult their GP or cardiologist before starting regular sauna bathing.

References

1. Hussain J & Cohen M (2018). Clinical Effects of Regular Dry Sauna Bathing. Evidence-Based Complementary and Alternative Medicine. [S001]
2. Beever R (2009). Far-infrared saunas for treatment of cardiovascular risk factors. Canadian Family Physician 55(7): 691–696. [S002]
3. Laukkanen JA, Laukkanen T, Kunutsor SK (2018). Cardiovascular and Other Health Benefits of Sauna Bathing. Mayo Clinic Proceedings 93(8): 1111–1121. [S004]
4. Kihara T, Biro S, Imamura M, et al. (2002). Repeated sauna treatment improves vascular endothelial and cardiac function in patients with chronic heart failure. Journal of the American College of Cardiology 39(5): 754–759. [S005]
5. Hannuksela ML & Ellahham S (2001). Benefits and risks of sauna bathing. American Journal of Medicine 110(2): 118–126. [S006]
6. Laukkanen T, Khan H, Zaccardi F, Laukkanen JA (2015). Association Between Sauna Bathing and Fatal Cardiovascular and All-Cause Mortality Events. JAMA Internal Medicine 175(4): 542–548. [S009]
7. Laukkanen T, Kunutsor S, Kauhanen J, Laukkanen JA (2017). Sauna bathing is inversely associated with dementia and Alzheimer's disease in middle-aged Finnish men. Age and Ageing 46(2): 245–249. [S010]
8. Kunutsor SK, Laukkanen JA (2023). Cardiovascular and other health benefits of sauna bathing: an updated systematic review and meta-analysis. Mayo Clinic Proceedings: Innovations, Quality & Outcomes. [S011]