On 2015 Apr 21, David Keller commented:

The observed association between sauna bathing and improved cardiovascular outcomes may be due to self-selection bias

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, thereby biasing the group of sauna-takers 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. Only randomized trials can provide the quality of evidence required for a physician to recommend a potentially dangerous intervention for health enhancement. Observational studies such as this one are supposed to be for "hypothesis generation" only.

On 2015 Apr 21, David Keller commented:

The observed association between sauna bathing and improved cardiovascular outcomes may be due to self-selection bias

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, thereby biasing the group of sauna-takers 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. Only randomized trials can provide the quality of evidence required for a physician to recommend a potentially dangerous intervention for health enhancement. Observational studies such as this one are supposed to be for "hypothesis generation" only.