> "We performed a prospective cohort study of a population-based sample of 2315 middle-aged (age range, 42-60 years) […] During a median follow-up of 20.7 years […] A total of 601, 1513, and 201 participants reported having a sauna bathing session 1 time per week, 2 to 3 times per week, and 4 to 7 times per week, respectively."
They are comparing the health differences of the number of sessions, using only people who claim to do sauna at least once a week over 20 years. They have nothing to say about lower frequency or no sauna at all.
They are comparing the health differences of the number of sessions, using only people who claim to do sauna at least once a week over 20 years. They have nothing to say about lower frequency or no sauna at all.