Key takeaways
In the Finnish KIHD cohort, men using a sauna 4–7 times a week had lower rates of sudden cardiac death, cardiovascular death and death from any cause
These are observational findings that may be partly explained by health, wealth and fitness
Sauna after training adds heat adaptation, but it complements exercise rather than replacing it
Saunas are suddenly everywhere: gyms are adding recovery suites, and "hot and cold therapies" climbed into the top 20 of the ACSM 2026 worldwide fitness trends survey. Much of the buzz rests on a series of studies from eastern Finland, where sauna bathing is part of everyday life. What did those studies actually find, and how much can we trust them?
The KIHD study
The Kuopio Ischaemic Heart Disease Risk Factor (KIHD) study recruited middle-aged men from eastern Finland in the 1980s and followed them for decades. In the landmark paper by Laukkanen T, et al., 2015 in JAMA Internal Medicine, 2,315 men aged 42 to 60 reported how often they used a sauna. Over a median of about 20 years:
- Men who used a sauna 4–7 times a week had a markedly lower risk of sudden cardiac death, fatal coronary heart disease, fatal cardiovascular disease and death from any cause than men who went once a week.
- Two to three sessions a week sat in between, suggesting a dose-response pattern.
- Longer sessions were also associated with lower risk.
Later analyses of the same cohort extended the pattern to other outcomes. Kunutsor and colleagues (2018) reported that frequent sauna use was associated with a lower risk of stroke in men and women.
| Outcome (KIHD cohort) | Sauna 2–3×/week vs 1× | Sauna 4–7×/week vs 1× |
|---|---|---|
| Sudden cardiac death | Slightly lower, not significant | Lowest risk |
| Fatal coronary heart disease | Lower risk | Lowest risk |
| All-cause mortality | Lower risk | Lowest risk |
| Stroke (Kunutsor 2018) | Slightly lower risk | Lowest risk |
Why sauna might help the heart
A review by Laukkanen JA, Laukkanen T and Kunutsor, 2018 in Mayo Clinic Proceedings summarised plausible mechanisms. Heat makes blood vessels widen and heart rate rise, a bit like light exercise. Short-term studies show lower blood pressure and better arterial function after sauna sessions, and repeated heat exposure may improve vessel health over time. Relaxation and lower stress may play a part too.
These mechanisms overlap with some of the benefits of aerobic fitness discussed in VO2max, heart disease and blood pressure.
The big caveats
This is where enthusiasm needs a brake.
- Observational, not causal. Nobody was randomised to sauna or no sauna. The studies show an association.
- Confounding. Men who could take a sauna almost every day may have had more free time, better housing, higher income or better health. Researchers adjusted for many risk factors, but not everything can be measured.
- Reverse causation. People who already feel unwell may avoid the heat, making regular users look healthier.
- Narrow population. The core cohort was middle-aged Finnish men using traditional Finnish saunas. Results may not apply to infrared cabins, women, younger people or other cultures.
Fitness matters too. In a joint analysis, Kunutsor et al., 2018 found that men with both high cardiorespiratory fitness and frequent sauna use had the lowest risk of cardiovascular death, and high fitness alone was strongly protective. Sauna is best seen as a possible add-on to exercise, not a substitute (see VO2max and longevity). You can check where your fitness stands with the VO2max calculator.
Sauna, endurance and VO2max
For athletes, sauna is also a tool for heat adaptation. In a small study by Scoon et al., 2007, six competitive male runners sat in a sauna for about 30 minutes after training sessions for three weeks. Their run time to exhaustion improved compared with control, along with an increase in plasma volume. The study was tiny and not blinded, so treat it as promising rather than settled.
Effects on VO2max itself in cool conditions are debated, as explained in heat training and VO2max. Sauna may make long runs in the heat easier, but it will not replace intervals (see how to improve VO2max). Heat stress also raises overnight heart rate, so keep an eye on resting heart rate and HRV after late sessions.
Practical tips
- Start with 5 to 10 minutes and build up gradually; the Finnish studies involved traditional, very hot saunas.
- Cool down slowly and drink water afterwards.
- After hard training, wait until you have rehydrated a little before getting in.
- Two or three sessions a week is a sensible routine if you enjoy it.
Safety: avoid alcohol before and during a sauna, as it raises the risk of fainting and dangerous heart rhythms. Leave immediately if you feel dizzy, nauseous or unwell. If you have unstable angina, a recent heart attack, severe aortic stenosis, low blood pressure, are pregnant or take medication that affects blood pressure, get medical advice first. Do not sauna when dehydrated or ill with a fever.
More studies on fitness and health are on the research page.
Frequently asked questions
How often should I use a sauna for heart health?
The Finnish studies found the lowest risks in people using a sauna 4 to 7 times a week, but this is an association, not a proven dose. Any regular use you enjoy and tolerate is reasonable.
Can sauna replace exercise?
No. In Finnish data, men with both high fitness and frequent sauna use had the lowest risk, and fitness itself was strongly protective. Use the sauna alongside training.
Is sauna safe with a heart condition?
Many people with stable heart disease tolerate sauna, but anyone with unstable angina, a recent heart attack, severe aortic stenosis or low blood pressure should get medical advice first and avoid alcohol in the sauna.
Sources
- Laukkanen T, et al. Association between sauna bathing and fatal cardiovascular and all-cause mortality events. JAMA Intern Med, 2015.
- Laukkanen JA, Laukkanen T, Kunutsor SK. Cardiovascular and other health benefits of sauna bathing: a review of the evidence. Mayo Clin Proc, 2018.
- Kunutsor SK, et al. Sauna bathing reduces the risk of stroke in Finnish men and women: a prospective cohort study. Neurology, 2018.
- Kunutsor SK, et al. Joint associations of sauna bathing and cardiorespiratory fitness on cardiovascular and all-cause mortality risk: a long-term prospective cohort study. Ann Med, 2018.
- Scoon GSM, et al. Effect of post-exercise sauna bathing on the endurance performance of competitive male runners. J Sci Med Sport, 2007.