In 2015, Jari Laukkanen and colleagues published the results of the Kuopio Ischemic Heart Disease Risk Factor Study in JAMA Internal Medicine. The study followed 2,315 Finnish men for 20 years, recording their sauna use at baseline and tracking cardiovascular events and mortality. The findings were striking: compared to men who used a sauna once per week, those who used it 4 to 7 times per week had a 40 percent lower all-cause mortality, a 50 percent lower fatal cardiovascular disease rate, and a 63 percent lower risk of sudden cardiac death, after adjusting for conventional cardiovascular risk factors including smoking, blood pressure, cholesterol, and physical activity.
The Cardiovascular Mechanism
A sauna session at 80 to 100 degrees Celsius produces a cardiovascular response comparable to moderate aerobic exercise. Heart rate rises to 100 to 150 beats per minute. Cardiac output increases. Peripheral vasodilation reduces blood pressure. Plasma volume expands over repeated sessions, improving cardiac preload. Arterial stiffness, measured by pulse wave velocity, reduces significantly with regular sauna use. These haemodynamic adaptations are the probable primary mechanism for the cardiovascular mortality benefit observed in the Kuopio cohort.
Heat Shock Proteins and Cellular Protection
Regular heat stress upregulates heat shock proteins, a class of proteins that repair misfolded proteins, protect cells from oxidative damage, and reduce inflammatory gene expression. Heat shock protein induction is one of the key mechanisms by which regular sauna use is thought to reduce mortality independently of its cardiovascular haemodynamic effects. Sauna use is associated with reductions in circulating CRP and IL-6 over 8 weeks in randomised trials, consistent with this anti-inflammatory mechanism.
Sources
- Laukkanen, T., et al. (2015). Association between sauna bathing and fatal cardiovascular and all-cause mortality events. JAMA Internal Medicine, 175(4), 542-548.
- Laukkanen, J.A., et al. (2018). Sauna bathing is inversely associated with dementia and Alzheimer's disease in middle-aged Finnish men. Age and Ageing, 46(2), 245-249.
- Kessler, W., et al. (2014). Heat-shock protein 60: evidence for receptor-mediated induction of the acute phase protein response. European Surgical Research, 52(3-4), 141-148.