ABSTRACT
Objective To explore the differences of memory functions and objective sleep parameters and their correlations in patients with insomnia disorder in different subtypes.Methods Eightynine patients with insomnia disorder,including 11 patients with difficulty initiating sleep(DIS),20 patients with early morning awakening(EMA),20 patients with difficulty maintaining sleep (DMS) and 38 patients with mixed sleep symptoms(MS) were enrolled between August 2012 and February 2014 in the Memory and Sleep Disorders Clinic of the First Affiliated Hospital of Anhui Medical University.Memory functions,including objective memory,spatial memory,working memory and reference memory were detected with nine boxes maze,and objective sleep profiles were assessed using polysomnography.Results The error numbers of spatial(H =15.404,P =0.002) and working (H =10.126,P =0.018) memories were significantly different among the 4 subtypes of patients,with more errors of spatial and working memory in the EMA (6.00 (5.00,8.00),5.00 (4.00,6.00)) and MS (5.00 (3.75,7.25),5.00 (2.75,7.00)) groups compared with the DMS (2.50 (2.00,4.00),2.00 (1.00,4.00)) group (tspstial =3.938,3.428;t =2.803,2.840;all P ＜ 0.05).Sleep efficiency(H =7.929,P =0.048),REM sleep time(F =2.840,P =0.043) and the percentage of REM sleep time on total sleep time (REM％;H =7.913,P =0.048) were also significantly different among the 4 subtypes of patients,with lower sleep efficiency in the MS(69.7％ (50.5％,78.7％)) group compared with the EMA (81.0％ (64.8％,86.4％)) and DMS (80.2％ (62.6％,88.9％)) groups (t =2.242,2.352;all P ＜ 0.05),less REM sleep time (min) and REM％ in the EMA(61.6 ±27.1,16.9％ (13.1％,21.9％)) and MS(56.9 ±31.4,16.9％ (11.5％,21.2％)) groups compared with the DMS (80.9 ± 32.7,22.3％ (18.5％,25.5％)) group (qREM time =3.791,5.397;tREM％ =2.513,2.612;all P ＜0.05).The error numbers of working memory and spatial memory negatively correlated with the REM sleep time (r =-0.387,-0.348;all P ＜ 0.05) and REM％ (r =-0.350,-0.354;all P ＜ 0.05).Conclusions There are discrepancies in the spatial and working memories and subtle differences in the objective sleep parameters among the patients with different subtypes of insomnia disorder.The worse memories in insomnia disorder patients might be associated with the decreased REM sleep.