Sauna Use and Heart Health: What a 15-Year Finnish Cohort Study Found

Sauna bathing is a daily habit for a large share of the Finnish population, which has made Finland the source of some of the largest and longest-running studies on sauna use and long-term health outcomes.

What the research looked at

A prospective cohort study tracked sauna bathing habits in 1,688 participants (mean age 63, 51.4% women) and followed them for a median of 15 years, recording cardiovascular disease (CVD) deaths over that period. This is a large, long-duration, real-world study design — not a short-term lab trial — which lets researchers see long-term associations between habits and health outcomes.

What they found

The risk of cardiovascular mortality decreased in a linear, dose-dependent pattern as sauna frequency increased, with no threshold effect. Compared to people who took one sauna session per week, the hazard ratio for CVD mortality was 0.71 for those with 2–3 sessions per week, and 0.23 for those with 4–7 sessions per week — after adjusting for standard cardiovascular risk factors. In plain terms, the most frequent sauna users had a substantially lower relative risk of dying from cardiovascular disease compared to the least frequent users, even after accounting for other health factors. Total weekly sauna duration was also linked to lower risk in a similarly continuous way.

What this means in practice

This is an observational cohort study, not a randomized trial — meaning it shows a strong, consistent association rather than definitive proof of cause and effect, since people who sauna more often may also differ in other health habits. But the size of the effect, the dose-response pattern, and the 15-year follow-up make this one of the more compelling pieces of long-term evidence for a wellness habit, and it's consistent with other Finnish cohort research on the same population.