Short read
Kunutsor and Laukkanen of the University of Bristol and the University of Eastern Finland analysed the Kuopio Ischaemic Heart Disease Risk Factor Study (KIHD), a prospective cohort, for a single endpoint: venous thromboembolism, the formation of blood clots in the veins. The analysis appeared as a short report in the European Journal of Epidemiology in 2019 and draws on the same population as the main cardiovascular analyses of the cohort.
Compared with less frequent sauna use in the same cohort, more frequent sauna use was associated with a lower risk of venous thromboembolism. The authors discuss better flow properties of the blood and an increased plasma volume as possible mechanisms. The entry used here gives no hazard ratio or event count for this analysis, so no figure is quoted.
The number of events is considerably smaller than in the main cardiovascular analyses, which makes the estimate less stable. As a short report, the paper contains fewer methodological details. No independent replication is known, and the data are observational, so they show an association and not a cause.
The finding extends the picture of vascular associations from the arteries to the venous system. Given the small event count and the missing replication, it is a secondary finding rather than a headline. It does not show that sauna use prevents blood clots in an individual.