Relationship between sleep disorders and cognitive impairment in patients with Alzheimer's Disease

Objective To investigate the clinical characteristics of sleep disorders(SD)in patients with Alzheimer's disease(AD), and the relationship between SD and cognitive impairment. Methods According to the inclusion and exclusion criteria of AD, 89 consecutive AD patients admitted to Beijing Tiantan Hospital from January 2016 to January 2017 were included.The Pittsburgh sleep quality index(PSQI)scale was used to evaluate the overall sleep status.The patients were randomized into the AD with SD(AD-SD)group(PSQI>7)and the AD without SD(AD-NSD)group(PSQI<7). The cognitive function of AD patients was evaluated by the Montreal cognitive assessment(MoCA)scale, and the overall cognitive function and cognitive domains were compared between the AD-SD and AD-NSD groups. Results Of the 89 AD patients, 71 cases(79.78%)had SD.There was no significant difference in gender, age, age of onset, education level and disease duration between the AD-SD and AD-NSD groups(P>0.05). The factors in the PSQI scale had significant differences between AD-SD和AD-NSD groups, including sleep quality, sleep latency, sleep duration, sleep efficiency, sleep disturbance, administration of sleeping medication and daytime dysfunction(P<0.05). Compared with the AD-NSD group, the AD-SD group showed that the total score of MoCA scale was significantly reduced(P<0.05), and the scores of delayed recall and language were significantly decreased(P<0.05). There was a negative correlation of the sleep time with the total score of MoCA scale and the score of delayed recall in the AD-SD group(r=-0.245 and -0.249, P=0.041 and 0.039). Night SD was negative correlated with the total score of MoCA scale and the score of delayed recall(r=-0.248 and -0.283, P=0.038 and 0.018). Conclusions The incidence of AD-SD is up to 79.78%.AD-SD patients have a worse subjective sleep quality, longer time to fall asleep, shorter sleep time, lower sleep efficiency, higher night SD, more use of sleep drugs and more daytime dysfunction.General cognitive dysfunction, delayed recall and language impairment are more obvious in AD-SD patients.In AD-SD group, longer time to fall asleep and night SD are related to the general cognitive function and delayed recall. Key words: Alzheimer disease; Sleep disorders; Cognition disorders