The DNA in our cells is like a book of instructions. Chemical tags can appear on its pages, and while they don't change the text, they decide which pages get read. Scientists can use these tags to estimate biological age, as if they were glancing at the margins of the book and seeing how worn it is. A new study tested what regular sauna sessions do to those tags.
18 firefighters sat in a portable sauna for 20 minutes at least four times a week. Blood was drawn before the course began and after 8-18 weeks. It turned out that eight age readings had changed: some clocks indicated that blood and lungs had grown "older." But when the researchers accounted for which immune cells were actually floating in the blood, all the changes disappeared.
It's like rearranging books in a library: the books themselves don't deteriorate, but if you gauge age by how battered the shelves are, you can draw the wrong conclusion. Now researchers know that when estimating age from blood, they must always check which cells are present. In the future, this will help measure more precisely how sauna, cold exposure, or exercise affects aging.
At the start of the study, the firefighters had a higher methylation-predicted maximal oxygen uptake (VO2max) than the control group, which makes sense for a profession requiring high physical fitness. At the same time, they also had a higher epigenetic damage score, DamAge, and a lower adaptation score, AdaptAge, which may reflect accumulated occupational stress.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.