Low sleep efficiency in patients with cognitive impairment.

Alzheimer's disease (AD) is the most common cause of dementias. Mild cognitive impairment (MCI) indicates the situation that a person has memory complaints and mild objective cognitive impairment but no evidence of dementia. Sleep disturbance, one of the behavioral and psychological symptoms of dementia (BPSD), frequently occurs in patients with AD or MCI. The alteration of sleep architectures in AD patients remains inconclusive. In this study, we conducted the polysomnography. (PSG) examination among patients with mild AD with cholinesterase inhibitors (N=10) or MCI (N=12) and age-matched nondemented controls (N=13). The results showed sleep efficiency, which was one of the important parameters for sleep quality was significantly lower in patients with MCI and AD (N=22), 79.14 +/- 11.06 % vs. 67.07 +/- 19.10 %, p=0.046. There were no statistic differences of sleep architecture but a trend of REM insufficiency in patients with MCI or AD. The mean scores of geriatric depression score (GDS) and Epworth sleepiness scale (ESS) did not differ among the three groups. Our study implicated maintenance of sleep was impaired in patients with cognitive impairment and it was independent with depressive symptoms.