Sleep abnormalities across different clinical stages of Alzheimer's disease: A systematic review and network meta-analysis.

Sleep disturbances play an important role in Alzheimer's disease (AD) pathology. However, it is unclear exactly how sleep changes across the AD continuum. To address this gap, we conducted a network meta-analysis to explore how sleep changes (self-reported sleep quality, daytime sleepiness, polysomnography (PSG) and actigraphy measured sleep) across the clinical stages of AD. We searched MEDLINE, EMBASE, and all EBM databases via OVID and Web of Science. Meta-analyses revealed that although sleep changes are more marked in AD dementia, there are sleep signatures in mild cognitive impairment (MCI) which may exist persistently in more advanced stage. For instance, the decreased sleep efficiency and rapid eye movement (REM) sleep percentage observed in MCI were more obvious in AD dementia, while the decreased slow wave sleep (SWS) was only observed in AD dementia but not in MCI. The increasing abnormalities in objective sleep may be considered as important indicators associated with active pathology across the AD continuum. Interventions to improve PSG measured total sleep time, SWS and REM would likely have potential for slowing AD progression, particularly if employed early in the disease process, e.g., in individuals with mild cognitive impairment due to AD or those with genetic risk for developing AD.