Short read
Laukkanen and colleagues followed 1,688 Finnish adults aged 53 to 74, with an average age of 63, in a prospective cohort study published in BMC Medicine in 2018. 51.4 % of the participants were women, which makes it the first cohort in this field that is not limited to men. Median follow-up was 15.0 years, with 181 fatal cardiovascular events. The authors also tested whether sauna habits add to the predictive power of established risk models.
Compared with less frequent sauna use in the same cohort, the risk of cardiovascular death was lower with every additional weekly session, in a linear pattern without a visible threshold. Total weekly time in the sauna was associated with risk on its own: more than 45 minutes a week compared favourably with up to 15 minutes. The association applied to women and men alike, and adding sauna frequency measurably improved long-term risk prediction.
With 181 events, the study is too small for detailed subgroup and dose-response analyses. Residual confounding is possible. Reverse causality, in which healthier people simply use the sauna more, cannot be ruled out, although sensitivity analyses that excluded the first five years of follow-up remained stable.
For readers who are not middle-aged Finnish men, this is the more relevant cohort, because it includes women. It describes an association in one Finnish population and says nothing about what an individual can expect from adding sessions.