Sauna Health Benefits: Heart Health Research from Finnish Studies

Before 2015, sauna and heart health research was scattered across small studies with inconsistent methodology. Then the Kuopio Ischemic Heart Disease Risk Factor Study (KIHD) published its sauna findings, and the conversation changed permanently. This wasn’t a 30-person pilot study or a cross-sectional snapshot. It was 2,315 middle-aged Finnish men tracked for over 20 years, with sauna habits documented at baseline and cardiovascular outcomes followed through hospital records and death certificates.

Here is what the data actually shows, where the study is strong, and where it falls short.

What Was the Finnish Sauna Heart Health Study?

The KIHD study tracked 2,315 middle-aged Finnish men for over 20 years, categorizing them by sauna frequency (1x, 2-3x, or 4-7x per week). Published in JAMA Internal Medicine in 2015, it is the most-cited piece of sauna-cardiovascular research in the literature.

The KIHD study was originally designed to investigate risk factors for ischemic heart disease in eastern Finland. Participants were men aged 42-60 at enrollment, recruited between 1984 and 1989 from the city of Kuopio and surrounding rural areas. Sauna bathing habits were assessed via questionnaire at baseline and categorized into three frequency groups:

• Group 1: 1 session per week (601 men)
• Group 2: 2-3 sessions per week (1,513 men)
• Group 3: 4-7 sessions per week (201 men)

The median follow-up period was 20.7 years. Outcomes were tracked through Finland’s national hospital discharge registry and cause-of-death registry, which are considered highly reliable due to Finland’s centralized health record system.

This study was published by Laukkanen et al. In JAMA Internal Medicine in 2015 and has since become the most-cited piece of sauna-cardiovascular research in the literature.

Does Sauna Use Reduce Cardiovascular Death Risk?

Yes. The KIHD data showed a 50% lower cardiovascular mortality rate in men who used a sauna 4-7 times per week compared to once per week, and a 40% lower all-cause mortality rate, after adjusting for major confounders.

The headline numbers from the KIHD sauna analysis, adjusted for conventional cardiovascular risk factors (age, BMI, systolic blood pressure, smoking, alcohol consumption, previous heart disease, diabetes, LDL cholesterol, physical activity level, and socioeconomic status):

The 4-7x/week group showed a 50% lower hazard ratio for cardiovascular mortality compared to the 1x/week group, after adjustment for all measured confounders. The confidence interval (0.33-0.77) doesn’t cross 1.0, indicating statistical significance at the 95% level.

For all-cause mortality, the pattern held: the 4-7x/week group had a 40% lower risk (HR 0.60, 95% CI 0.46-0.80) compared to 1x/week.

Does Sauna Use Lower the Risk of Sudden Cardiac Death?

Yes. Men who used a sauna 4-7 times per week had a 63% lower risk of sudden cardiac death compared to those using it once per week. The most striking finding from the KIHD study. Session duration also mattered: sessions longer than 19 minutes showed additional benefit.

The most striking finding was for sudden cardiac death (SCD), defined as death occurring within 24 hours of symptom onset due to cardiac cause:

A 63% lower risk of sudden cardiac death in the 4-7x/week group. The 2-3x/week result wasn’t statistically significant for SCD specifically (the confidence interval crosses 1.0), but the 4-7x/week result was significant.

Session duration also mattered independently. Men who reported sessions longer than 19 minutes had lower SCD risk compared to those with sessions under 11 minutes (HR 0.48, 95% CI 0.31-0.75).

Can Sauna Use Reduce Stroke Risk?

The KIHD data suggest yes. Men using a sauna 4-7 times per week had a 62% lower risk of stroke compared to once per week. However, the high-frequency group was small (201 men), so the point estimate carries meaningful uncertainty despite reaching statistical significance.

A subsequent analysis of the same KIHD cohort, published in Neurology in 2017 by Kunutsor et al., examined stroke outcomes:

The 4-7x/week group showed a 62% lower risk of stroke. The 2-3x/week result was a 12% reduction but didn’t reach statistical significance. Over the follow-up period, 155 incident stroke events were recorded. The absolute numbers in the 4-7x/week group were small (n=201 men), which means the point estimate (62% reduction) comes with meaningful uncertainty despite the confidence interval clearing significance.

Does Regular Sauna Use Lower Blood Pressure?

The KIHD data show a 46% lower risk of developing hypertension in men who used a sauna 4-7 times per week, and a 24% lower risk at 2-3 times per week. Both results reached statistical significance.

A 2017 analysis by Zaccardi et al. Using the KIHD data examined incident hypertension (new diagnosis during follow-up among men without hypertension at baseline):

A 24% lower risk at 2-3x/week and 46% lower risk at 4-7x/week. Both reached statistical significance. This analysis was based on 251 men who developed hypertension during follow-up out of 1,621 who were normotensive at baseline.

What Does a Sauna Do to Your Heart and Blood Vessels?

During a Finnish sauna session, heart rate rises to 100-150 bpm (comparable to moderate exercise), blood pressure drops by an average of 7/3 mmHg, arterial stiffness decreases measurably, and endothelial function improves. These acute effects persist for 30-60 minutes post-session.

The acute physiological responses during a sauna session are well-characterized across multiple smaller studies:

Heart Rate

Heart rate increases from resting levels (60-80 bpm) to 100-150 bpm during a typical Finnish sauna session at 80-100 degrees Celsius. This is comparable to moderate-intensity aerobic exercise (brisk walking, easy cycling). The increase is driven by thermoregulatory demands: as core body temperature rises, cardiac output must increase to shuttle blood to the skin surface for cooling.

A 2019 study by Ketelhut and Ketelhut measured heart rate responses in 19 participants and found mean heart rates of 120-140 bpm during sauna, equivalent to approximately 60-70% of age-predicted maximum heart rate.

Blood Pressure

The blood pressure response has two phases:

1. During the session: Systolic blood pressure may transiently increase in the first few minutes, then typically decreases as vasodilation progresses. Diastolic pressure generally decreases throughout. A 2017 study by Laukkanen et al. Measuring 100 participants found that a 30-minute sauna session reduced systolic blood pressure by an average of 7 mmHg and diastolic by 3 mmHg immediately post-session.

2. Post-session: Blood pressure typically remains reduced for 30-60 minutes after exiting the sauna. Some studies have shown persistent reductions lasting several hours.

Vascular Compliance

Arterial stiffness, measured by pulse wave velocity (PWV), decreases acutely after sauna use. A 2018 study published in the Journal of Human Hypertension found that a single 30-minute sauna session at 73 degrees Celsius reduced carotid-femoral PWV from 9.8 to 8.6 m/s (a clinically meaningful improvement in arterial compliance) in a group of 102 participants. The reduction persisted for at least 30 minutes post-session.

Endothelial Function

Flow-mediated dilation (FMD), a measure of endothelial function, appears to improve with regular sauna use. A small 2018 study (n=30) found that 8 weeks of regular sauna bathing (4-5x/week) improved brachial artery FMD from 5.1% to 7.8%. Endothelial dysfunction is an early marker of atherosclerosis, so if this finding replicates, it could be one mechanism linking sauna use to lower cardiovascular events.

What Did the Mayo Clinic Review Conclude About Sauna and Heart Health?

The 2018 Mayo Clinic Proceedings review concluded that the association between frequent sauna bathing and reduced cardiovascular mortality is robust, with a dose-response relationship that strengthens the case for a real biological effect. It brought sauna-cardiovascular data into mainstream cardiology literature.

In 2018, Laukkanen, Laukkanen, and Kunutsor published a comprehensive review in Mayo Clinic Proceedings titled “Cardiovascular and Other Health Benefits of Sauna Bathing.” This review synthesized the KIHD findings with other available evidence and concluded:

• The association between frequent sauna bathing and reduced cardiovascular mortality is robust and persists after adjustment for multiple confounders.
• The dose-response relationship (more frequent bathing correlates with lower risk) strengthens the case for a real biological effect rather than pure confounding.
• Proposed mechanisms include improved endothelial function, reduced arterial stiffness, modulation of the autonomic nervous system, reduced systemic inflammation, and beneficial effects on lipid profiles.
• The review explicitly noted that the evidence base is still predominantly observational and called for randomized controlled trials.

The Mayo Clinic Proceedings publication was significant because it brought the sauna-cardiovascular data into a mainstream medical journal with wide readership among practicing cardiologists and internists.

What Are the Limitations of the Sauna Heart Health Research?

The KIHD study is observational (not a randomized trial), so it can’t prove causation. Key limitations include healthy user bias, an all-male Finnish population, self-reported sauna habits, no differentiation by sauna type, and a small high-frequency group of only 201 men.

These are critical to understand, and any article on this topic that doesn’t address them is doing you a disservice.

1. Observational Design (Correlation, Not Causation)

The KIHD study is a prospective cohort study, not a randomized controlled trial. Participants weren’t randomly assigned to sauna frequency groups. This means we can’t conclude that sauna bathing caused the lower cardiovascular mortality. The association is strong and dose-dependent, but the possibility of unmeasured confounding remains.

2. Healthy User Bias

People who sauna 4-7 times per week may be healthier in ways that weren’t captured by the measured confounders. They may have better diets, lower stress, stronger social networks (communal sauna culture), more stable employment, or other health-promoting behaviors that correlate with frequent sauna use but weren’t adjusted for. The study controlled for physical activity, BMI, smoking, alcohol, and socioeconomic status, but these adjustments can’t eliminate all confounding.

3. All-Male Finnish Population

Every participant was a middle-aged Finnish man from eastern Finland. We can’t directly extrapolate these findings to women, younger adults, older adults, or non-Finnish populations. Finnish men grow up in a sauna culture and may have different physiological adaptations or behavioral patterns around sauna use compared to someone who starts sauna bathing at age 50 in the United States.

A 2018 study by Kunutsor et al. Using the FINRISK population (both men and women, n=1,688) did find similar associations in women, but with smaller sample sizes and shorter follow-up.

4. Self-Reported Sauna Habits

Sauna frequency and duration were assessed by questionnaire at baseline. They weren’t objectively measured over the follow-up period. Participants may have changed their sauna habits during the 20-year follow-up, and there was no accounting for this. Additionally, self-reported session durations may not be accurate.

5. No Differentiation by Sauna Type

The KIHD study participants used traditional Finnish saunas (electric or wood-fired, dry heat with intermittent steam). The findings can’t be directly applied to infrared saunas, steam rooms, or other heat therapy modalities, which operate at different temperatures and through different heat transfer mechanisms.

6. Small High-Frequency Group

Only 201 men (8.7% of the cohort) were in the 4-7x/week group. While the hazard ratios for this group were striking, the small sample size means the confidence intervals are wide. A few outcome events more or less in this group would meaningfully shift the point estimates.

How Often Should You Sauna for Heart Health Benefits?

The KIHD data suggest frequency matters more than intensity. Four or more sessions per week at moderate temperatures (average 79°C) and 15-minute sessions appeared to be in the beneficial range. You don’t need to push to extreme temperatures or durations.

If you are using a traditional Finnish sauna and want to consider the cardiovascular data in your practice:

The KIHD participants averaged 79 degrees Celsius (measured at thermostat level, not bench level) and 14.2-minute sessions. These are moderate parameters by Finnish standards. You don’t need to push to 100+ degrees Celsius or endure 30-minute sessions to align with the study conditions. For a detailed breakdown of how temperature and duration interact with health outcomes, see our temperature and duration protocol guide.

The dose-response relationship in the data suggests that frequency matters more than intensity. Four sessions per week at 80 degrees Celsius and 15 minutes each appeared to be in the beneficial range.

The cardiovascular mechanisms discussed above also have implications for brain health. Improved vascular function, reduced inflammation, and autonomic nervous system regulation are all relevant to neurological outcomes. We cover the KIHD cohort’s dementia and Alzheimer’s findings in our brain health article.

Is the Evidence Strong Enough to Recommend Sauna for Heart Health?

The KIHD study is the strongest piece of evidence linking regular sauna use to reduced cardiovascular disease risk. A 50% lower cardiovascular mortality rate and 63% lower sudden cardiac death rate in the 4-7x/week group are large effect sizes that survived adjustment for major confounders. The dose-response relationship and biological plausibility strengthen the case.

But this is observational data from a specific population. It demonstrates a strong association, not proven causation. Healthy user bias can’t be ruled out. The findings haven’t been replicated in a large randomized trial, and they come exclusively from Finnish men using traditional saunas.

If you already sauna regularly, the data is encouraging. If you are considering starting, the cardiovascular evidence is one of the more compelling reasons to do so. But don’t treat these numbers as guarantees, and don’t use sauna as a replacement for established cardiovascular risk management (exercise, diet, blood pressure control, medication when indicated).