Can Sauna Therapy Help Chronic Heart Failure? An Early Study Says Maybe

This 2002 study is the one that put "Waon therapy" — a specific, medically supervised form of dry infrared sauna therapy developed in Japan — on the map for heart failure research. It's small and dated, but it was published in one of cardiology's top journals and laid the groundwork for a whole line of later research.

What the research looked at

Published in the Journal of the American College of Cardiology in 2002, this study enrolled 20 patients with chronic heart failure. Participants sat in a dry sauna at 60°C for 15 minutes, then rested wrapped in a blanket for 30 minutes to sustain the warming effect, once daily for two weeks. Researchers measured flow-mediated dilation (a marker of blood vessel health) and blood levels of BNP, a hormone that rises when the heart is under strain.

What they found

Clinical symptoms improved in 17 of the 20 patients. Flow-mediated dilation increased significantly after two weeks of sauna treatment, and BNP levels dropped — with the improvement in blood vessel function correlating with the drop in BNP. A comparison group that didn't receive sauna therapy showed no change in either measure over the same period.

What this means in practice

This is a small, early-stage study — 20 patients, and the comparison wasn't a randomized, blinded design, so it can't rule out other explanations for the improvement. It also used a specific medical protocol under supervision, not a casual home sauna session, and heart failure is a serious condition that needs to be managed by a cardiologist. But it's a genuinely interesting signal from a top-tier journal, and it's the foundation a larger body of Waon therapy research has since built on.