Does Sauna Bathing Improve Blood Vessel Health in Heart Disease? A Randomized Trial Says Not Necessarily

Not every sauna study returns a positive result — and this one is worth including precisely because it doesn't. Honest research includes trials that come back negative, and this randomized trial in patients with existing heart disease is a good example of the evidence being more mixed than the observational cohort studies alone suggest.

What the research looked at

Published in the Journal of Applied Physiology in 2023, this randomized controlled trial enrolled 41 adults with stable coronary artery disease. Participants were randomly assigned to eight weeks of unsupervised Finnish sauna bathing, four sessions per week, or a control condition. Researchers measured brachial artery flow-mediated dilation, central arterial stiffness, and both systolic and diastolic blood pressure before and after the intervention.

What they found

After eight weeks, none of the measured markers differed significantly between the sauna group and the control group — flow-mediated dilation, arterial stiffness, and blood pressure all changed similarly in both groups.

What this means in practice

This trial is a useful counterweight to the large Finnish cohort studies linking frequent sauna use to lower cardiovascular mortality over many years — it suggests that in people who already have coronary artery disease, eight weeks of moderate sauna use may not be enough, by itself, to measurably shift these specific vascular markers. It doesn't mean sauna use is unsafe for people with heart disease (the trial reported none), just that any benefit may take longer to appear, require a different protocol, or show up in different measures than this study captured. Anyone with existing heart disease should talk to their cardiologist before starting regular sauna use.