Static postural stability and neuropsychological performance after awakening from REM and NREM sleep in patients with chronic insomnia: a randomized, crossover, overnight polysomnography study

Study Objectives: Chronic insomnia disorder (CID) is a common sleep disorder, with a prevalence ranging from 6%-10% worldwide. Individuals with CID experience more fragmented sleep than healthy control patients do. They awaken frequently during the night and have a higher risk of injury from falling. Awakening from different sleep stages may have different effects on postural stability and waking performance. However, limited research has been conducted on this topic. Methods: This prospective randomized crossover study was conducted between January 2015 and January 2017. We included 20 adults aged 20-65 years who fulfilled the diagnosis criteria for CID. Participants underwent 2 overnight polysomnography studies with an interval of at least 7 days. They were awakened during either rapid eye movement (REM) sleep or stage N1/N2 sleep alternatively. We compared measurements of static postural stability, vigilance scores, and neuropsychological tests between REM sleep and stage N1/N2 sleep awakening. Results: Polysomnography parameters between the 2 nights were comparable. Participants who were awakened from REM sleep had worse static postural stability than those with stage N1/N2 sleep awakening. Compared with stage N1/N2 sleep awakening, larger mean sway areas of center of pressure (P =.0413) and longer center-of-pressure mean distances (P =.0139) were found in REM sleep awakening. There were no statistically significant differences in vigilance scores or neuropsychological tests between the 2 nights. Conclusions: REM sleep awakening was associated with worse static postural stability than was stage N1/N2 sleep awakening. No statistically significant differences were found in waking performance in alertness or in neuropsychological tests between stage N1/N2 and REM sleep awakening.