Clinical Implication of Korean Dry Sauna Therapy

To the editor

I would like to congratulate Choi et al. [1] for their successful study on Korean dry sauna therapy where the health-related quality of life of obese people had improved without any adverse events. The therapy included 15 minutes of dry sauna at 90°C, twice daily for 4 consecutive days. Given our experience of Japanese dry sauna therapy in patients with advanced heart failure [2], I have several concerns regarding their protocol and future perspectives.

In our Japanese prospective randomized control trial [2], we performed Waon therapy with 15 minutes of dry sauna at 60°C, once daily for 10 days. While the frequency of twice daily might be more effective than once daily, it might reduce the participants’ adherence. An explanation of the implications of a twice-daily protocol would be helpful. The sauna temperatures were also different between the two studies (90°C versus 60°C) [1,2]. It would be interesting to compare the outcomes stratified by temperature settings.

The therapeutic effects on the hemodynamics and autonomic nervous systems would be evident immediately [3], but it might be weeks or months until the metabolic benefits can be enjoyed. Long durations of dry sauna therapy may be required to assess its implications for obesity-related metabolic diseases.

Finally, as the authors stated in the limitations section [1], objective parameters might be useful for quantifying the impact of dry sauna therapy on the quality of life, including blood catecholamine levels and heart rate variability [3].