“Regular sauna use extends lifespan”

## The Evidence Laukkanen et al. published their prospective cohort study in *JAMA Internal Medicine* (2015), following 2,315 Finnish men for 20 years. Compared to once-weekly sauna users, men who used the sauna 4–7 times/week had a 40% lower risk of cardiovascular mortality and 24% lower all-cause mortality. A follow-up 2018 paper extended these findings to include stroke risk. ## Mechanisms Heat stress activates heat shock proteins, improves arterial compliance, reduces systemic inflammation (CRP), lowers blood pressure, and mimics some cardiovascular exercise adaptations. Regular hyperthermia has been shown to improve endothelial function independently of physical activity. ## Caveats The study is observational — Finnish sauna culture is embedded in a specific lifestyle context. RCTs are difficult to conduct for this exposure. Alcohol consumption combined with sauna (common in the study population) increases cardiovascular risk; the benefit may be partly from what sauna use replaces. No equivalent data exist for infrared saunas.