Sauna Science

Sauna bathing is a health habit associated with better hemodynamic function; however, the association of sauna bathing with cardiovascular and all-cause mortality is not known.

Most sudden cardiac deaths (SCDs) occur in the general population, and most SCDs occur outside the hospital with few or no early warning signs.1 Therefore, ascertainment of lifestyle characteristics that could be protective against SCD is important. Although some studies2- 4 have found sauna bathing to be associated with a better cardiovascular and circulatory function, the association between regular sauna bathing and the risk of SCD and fatal cardiovascular diseases (CVDs) is not known. Long-term sauna bathing has been associated with lower blood pressure and enhanced left ventricular function and thus potentially with reduced CVD risk. Sauna bathing leads to skin sweating–induced fluid loss and increase in heart rate, which are physiologic responses to warm temperature.5,6

Previous studies have found some positive effects of thermal exposure on CVD risk factors; however, the long-term effects of sauna bathing on risk of cardiovascular events, including the association between the frequency and duration of sauna bathing and the risk of SCD, are not well defined. The aim of this prospective study was to investigate the association between exposure to sauna bathing and the risk of SCD, fatal coronary heart disease (CHD), fatal CVD, and all-cause mortality events in the general male population.

Study Population

The study was approved by the Research Ethics Committee of the University of Eastern Finland, Kuopio. Each participant gave written informed consent. This study (Finnish Kuopio Ischemic Heart Disease Risk Factor Study) was designed to investigate risk predictors for atherosclerotic cardiovascular outcomes in a population-based sample of men from Eastern Finland. Participants were a randomly selected sample of 3433 men aged 42 to 60 years who resided in Kuopio, Finland, or its surrounding rural communities.7 Of those invited, 2682 (78.1%) participated in the study, and those with complete information on sauna bathing were included (N = 2327). Twelve men who did not use a sauna were excluded, leaving 2315 participants for the analyses. Baseline examinations were conducted from March 1, 1984, through December 31, 1989.

Assessment of Sauna Bathing

A traditional Finnish sauna has dry air (humidity 10%-20%) with a relatively high temperature. The recommended temperature for a sauna is usually 80°C to 100°C at the level of the bather’s face. Humidity is temporarily increased by throwing water on the hot rocks of the sauna heater. Sauna bathing was assessed by a self-administrated questionnaire based on weekly sauna bathing sessions, duration, and temperature. The assessment represents typical sauna use during the week. The temperature in the sauna room was measured using a thermometer in the sauna and self-reported. The questionnaires were checked by an experienced nurse at the time of baseline examination.

The Link Between Sauna Bathing and Mortality May Be Noncausal

Yoram Epstein, PhD; Yehuda Shoenfeld, MD

In their recent report, Laukkanen et al1 summarize a 25-year longitudinal study, indicating that regular sauna bathing (4-7 times per week) is associated with a reduced risk of cardiovascular diseases and all-cause mortality. We would like to suggest that regular sauna bathing is an indicator for a healthy lifestyle. Adopting habits of frequent physical activity, avoiding rich food high in saturated fat, and allowing for more relaxation and leisure time have been proven to be the best measures against many diseases and are also associated with improved health and longevity. Laukkanen et al do not provide data to explain this observation, but other studies suggest that regular sauna bathing lowers blood pressure, improves endothelial function, increases left ventricular ejection fraction, and reduces total and low-density lipoprotein cholesterol levels.2,3 Clinical and laboratory data on sauna bathing and its effect on diminishing cardiovascular risk factors (eg, metabolic syndrome symptoms) should be the aim for further studies.

Sauna use and cardiovascular mortality

David L Keller

I submitted the following letter to JAMA-IM on 4/18/2015:

Laukkanen and colleagues note an association between increased frequency of sauna bathing

and decreased risk of adverse cardiovascular events. Their observational study does not

establish that sauna bathing causes better cardiac health; rather, their results may be due to

self­-selection. Persons at higher risk for adverse cardiac events may experience unpleasant

symptoms due to the tachycardia induced by sitting in a hot sauna, such as mild dyspnea,

orthostasis, or chest discomfort, at higher frequency or severity than persons in good

cardiovascular health, These adverse symptoms might cause them to avoid saunas as much

as possible, thereby biasing the group of frequent sauna­ bathers to include persons at lower

risk of adverse cardiac events than the general public.

The authors suggest that, based on this study, \"sauna bathing is a recommendable health

habit\". I disagree, and suggest that physicians should await the results of a randomized trial of

sauna bathing before we recommend it for health enhancement.