Clinical Effects of Regular Dry Sauna Bathing: A Systematic Review.

Plain-language summary

This systematic review set out to test the health claims made for regular dry sauna use, because the claims are common and the evidence behind them had never been gathered in one place. It pooled 40 studies covering 3855 people, published from 2000 onward. Most were small, under 40 people each, and only 13 randomly assigned anyone to anything. Most of the studies reported a health benefit, but the review does not name which benefits, and does not name any benefit that was tested and came back with no relationship. So it establishes that the weight of the evidence points favorably and not what it points favorably at. The one specific outcome it does name is an adverse one, and it comes from a single 10-man study: sauna disrupted sperm production, and that reversed once the men stopped.

Key findings

• Forty studies covering 3855 people met the criteria. Most had under 40 people and only 13 randomly assigned participants to anything.
• Most of the 40 reported a health benefit. The review does not name which benefits were found, and does not name any that were tested and showed no relationship.
• The one adverse outcome named is disrupted sperm production, from a single 10-man study, and it reversed once the men stopped using the sauna.
• The authors say the frequency and duration that would produce a given health effect is still unsettled, and so is which people benefit most.