Short read
Podstawski and colleagues from several Polish universities published this study in Frontiers in Public Health in 2024. They recruited 22 female students aged 18 to 27 who had been in a sauna only one to three times in their lives. Each sat 20 minutes in the same dry sauna at 80 degrees and 14 to 16 % humidity, and a week later 20 minutes at 120 degrees and 12 to 14 %, followed each time by 6 minutes of recovery including 1 minute in cold water.
Compared with the session at 80 degrees, where nobody fainted, 3 of the 22 women lost consciousness at 120 degrees after around 18:30 minutes and had to leave before the end. Vomiting and confusion preceded the fainting and were the strongest predictors. Heart rate rose from 79.27 to 114.23 beats a minute at 80 degrees and from 82.68 to 120.95 at 120 degrees, a difference between the sessions that was not significant. At 80 degrees blood pressure fell and mood improved; at 120 degrees mood got worse.
The sample is small and consisted of young women only. The order was fixed, 80 degrees first and 120 degrees second, rather than randomised. 120 degrees is far above usual sauna temperatures, so the study compares a common condition with an extreme one. It does not say where in the cabin the women sat.
It is the only study in this collection on people with almost no sauna experience. It shows that extreme heat can make inexperienced users faint near the end of a session. The authors conclude that 80 degrees suits women who use the sauna only occasionally; that is their reading of 22 participants, not a general rule for beginners.