Comment by gjulianm
8 hours ago
That might have an effect, but these studies are probably mostly selecting for people who can tolerate a hostile environment for longer, which are usually healthier. I find it unlikely that sauna alone explains the fantastic, almost miraculous hazard ratios that these studies report.
Unfortunately, yes, just about everything beyond the basics in longevity stuff has that as a possible confounder. Sauna is a fairly passive thing, though, I would expect less of an effect.