Sauna Benefits and Risks: What the Observational Data Say and Who Should Be Careful

Sauna Benefits: The Type of Evidence Matters

After our detailed look at Sauna and Longevity, this article covers benefits and risks in one place. An important note: the data on benefits are mostly observational, comparing frequent and infrequent sauna users; that does not prove sauna causes the benefit.

What the Observational Data Show

In the Kuopio study published in JAMA Internal Medicine in 2015, 2,315 Finnish men aged 42-60 were followed for a median of 20.7 years.

• Sudden cardiac death: adjusted hazard ratio 0.37 (95% CI 0.18-0.75) for 4-7 sessions per week vs 1 session; 0.78 for 2-3 sessions (not significant).
• Other outcomes: similar associations were reported for fatal coronary heart disease, cardiovascular death and all-cause mortality.
• Duration: for sessions longer than 19 minutes, the sudden cardiac death hazard ratio was 0.48 vs sessions under 11 minutes; there was no significant duration association for all-cause mortality.
• Dementia: in a 2017 analysis of the same cohort in Age and Ageing, the dementia hazard ratio for 4-7 sessions per week was 0.34 (95% CI 0.16-0.71).

This cohort consists only of middle-aged Finnish men in a society with a sauna culture. Frequent sauna use may also be a marker of other healthy habits, which the study cannot fully separate.

Risks and Precautions

According to a review in the American Journal of Medicine (Hannuksela and Ellahham, 2001), sauna is well tolerated by most healthy adults, but:

• Contraindications: unstable angina pectoris, recent myocardial infarction and severe aortic stenosis are listed as contraindications. For many people with stable angina or an old heart attack, it was found safe.
• Alcohol: alcohol during sauna raises the risk of hypotension, arrhythmia and sudden death and should be avoided.
• Skin: sweating can increase itching in atopic dermatitis.
• Fertility (men): the review states sauna does not influence fertility; however, in a 2013 Human Reproduction study of 10 men, two 15-minute sessions a week at 80-90°C for three months markedly reduced sperm count and motility, and the effect was reversible. The difference between these two findings cannot be settled here; men planning a child should consult a physician.

In pregnancy, cardiovascular disease, low blood pressure or regular medication use, make the sauna decision together with a physician.

Limitations

• The main benefit data are observational and come from men in a single country.
• Sauna frequency and duration were self-reported.
• The figures for session length and frequency are observed associations, not recommendations.
• The sperm study is very small (10 people); results cannot be generalized.

Frequently Asked Questions