Sleep disturbance in mild cognitive impairment: a systematic review of objective measures

Sleep disturbance frequently occurs in patients with mild cognitive impairment (MCI) and appears to be involved in the cellular and molecular mechanisms of cognitive decline. The aim of this systematic review is to clarify whether patients with MCI demonstrate alterations in certain sleep parameters: total sleep time (TST), sleep efficiency (SE), sleep latency (SL), rapid eye movement latency (REML), percent of rapid eye movement (REM%), arousal index (AI), wake after sleep onset (WASO), slow-wave sleep (SWS), periodic leg movement in sleep (PLMS), and cyclic alternating pattern (CAP) through polysomnography (PSG) and actigraphy. Databases including PubMed, Web of Science, Embase, ScienceDirect, Cochrane, CBM, CNKI, Wanfang Data, and VIP were searched up to January 2016 to collect literature on the correlation between sleep disturbance and MCI as assessed by objective measures. Meta-analysis was conducted using the Review Manager 5.3 software. A total of ten case-control studies involving 225 MCI patients and 235 healthy elders (HE) were deemed eligible and included in our meta-analysis. Every type of sleep disturbance was present in our studies with significant differences in the MCI subtypes. Compared with HE, overall MCI patients as a group expressed more SL and less SE; MCI patients showed less TST and SE and more SL and CAP; patients with amnestic mild cognitive impairment (aMCI) had less AI; patients with non-amnestic mild cognitive impairment (naMCI) had more TST and less AI. Patients with naMCI expressed more AI than those with aMCI. The results indicate that MCI patients might experience more serious sleep disturbance and that different MCI subtypes have different patterns of sleep disturbance.