When looking at any of these studies in CPAP, and sleep in general, we need to be looking deeper than just the AHI (hypopnia index, how many times you stopped breathing), and directly at EEG measures of restorative function and other biomarkers.<p>This shows an improvement in AHI, but no change in any markers of actual sleep restorative function (I'd use the term "quality" but the sleep health industry has stolen that term to mean measures of sleep time).<p>When looking at sleep time the study shows no change in most of the sleep architecture, but a significant decrease in REM time, which can have effects on emotional wellbeing, irritability, and potentially depression.<p>This study showed no change in ESS (subjective measures of daytime sleepiness), but did show a change in PROMIS, which is a longer term measure of fatigue.<p>I've been recommending to anyone on CPAP that they give mandibular splint, which is a biteplate which shifts the jaw in order to hold the airway open, and is much easier, lower cost, and effective for many people. It also does not show a reduction in REM.<p>However, I also don't believe there is any reason that a sleep study which has full PSG relies only on sleep time, and none of the bio/neurological measures of health which are easily available, such as HRV, delta power, spindle activity, etc. etc.