Finsko, glad to be of help.
I have to admit I have a few reservations about that particular study, but then again most studies I read about OSA leave me feeling very frustrated.
My biggest issue is that over time the criteria and definition for what constitutes an hypopnea have changed and this has resulted in more people being diagnosed with OSA and SDB than back in 1988. I believe that this accounts quite a lot for the "epidemic" in recent years in the prevalence of OSA and SDB.
Yet no changes have been made in what is considered mild, moderate and severe OSA.
So an AHI of say 4 using the 4% desaturation criterion could now be an AHI of say 18 using the newer AASM 2012 definition. (If I am interpreting this incorrectly please anyone feel free to correct me!)
These changes are almost never addressed in longitudinal studies that are still using the older criteria.
Anyway, here's a commentary that was published discussing this study and it raises some interesting questions about using an AHI of zero for the reference group (which largely comprised very healthy, most likely pre menopausal women.) rather than the standard use of a group with an AHI of less than or equal to 5.
So, did this skew the results (for women especially), and also for the entire cohort?
https://academic.oup.com/sleep/article/38/5/659/2416838