Study Of Memory Functions And Sleep Electroencephalogram The Patients With Primary Insomnia

Background: Insomnia refers patients who have enough sleep time, appropriatesleep environment and opportunities, but subjectively experience difficulty in fallingasleep or maintaining sleep, so that the sleep duration and/or sleep quality do not meetthe individual physiological needs, and affect the daytime functions[1]. Insomnia canlead to the damage of cognitive function, including attention, alertness, and executivefunction, especially memory decline. Sleep EEG records the electrical activity of thebrain during sleep according to the sleep monitoring of physiological parameters toevaluate the sleep quality. The changes of sleep EEG is closely related to the daytimefunctions damage.Objective: To investigate the sleep quality and memory function in patients withprimary insomnia (PI) and its two subtypes, explore the correlation between sleepelectroencephalogram and memory.Methods: According to Diagnostic and Statistical Manual of Mental Disorders-IV(DSM-Ⅳ) and International Classification of Sleep Disorders-2(ICSD-2) diagnosticcriteria, we collected PI as the patient group, including psychophysiological insomnia（Psy-I）and paradoxical insomnia (Para-I), the normal population as the control group.The background information such as gender, age, educational level was matched.Hamilton Depression Scale17items (HAMD-17) and the Hamilton Anxiety Scale(HAMA) were used to measure depression and anxiety. We evaluated the subjectiveinsomnia by Pittsburgh Sleep Quality Index (PSQI) and the objective insomnia by polysomnography (PSG). Their gross cognitive function was measured by MontrealCognitive Assessment Scale (MoCA), spatial memory and object memory weremeasured by nine-boxes maze, object recognition memory was detected by picturerecognition test.Results:①Background information: there was no significant difference amonggroups in sex, age and the years of education. The total scores of PSQI, HAMD andHAMA were higher in the PI group than those in the normal group (Ps <0.05); therewere no significant difference between Psy-I and Para-I groups (Ps>0.05). MoCAscore in the PI group was significant lower than that in the control group (P<0.05).Further, the MoCA scores in both Psy-I and Para-I was lower than that in the normalgroup (Ps<0.05), and there was no significant difference between the two insomniacsubgroups.②Memories: the erroneous numbers of spatial working memory in the PIgroup were more than those in the control group (Ps<0.05). Both Psy-I group andPara-I group showed poor spatial working memory comparing to the control group(Ps<0.05), but there was no significant difference between the two PI subtypes groups.Object reference memory, object working memory, spatial reference memory andobject recognition was no significantly difference among various groups.③Electroencephalogram: compared to the control group, the sleep parameters wassignificant difference in the PI group (Ps<0.05)(i.e. delay sleep latency, increased totalsleep time, reduced sleep efficiency, and lowed the REM duration and its proportion,and N3duration and its proportion). The results in the Psy-I group was the same as thecontrol group (Ps<0.05). The REM duration and its proportion, N3duration and itsproportion in the Para-I group was significantly decreased compared to the controlgroup (Ps<0.05). Compared to the Para-I group, the Psy-I group had reduced totalsleep time, prolonged sleep latency, decreased sleep efficiency, and increased N2duration (Ps<0.05).④Relationships between cognitive and the sleep parameters: Spearman correlation analysis showed that the total score of MoCA positivelycorrelated to the N3proportion (r=0.234, P=0.006). The errors of spatial referencememory was positively correlated to the N1duration and its proportion (r=0.295, P=0.002; r=0.285, P=0.010). The errors of spatial working memory positivelycorrelated to durations of REM and N1, and the N1proportion (r=0.274, P=0.020; r=0.270, P=0.033; r=0.244, P=0.040), but negatively correlated to the duration ofN3and its proportion (r=–0.277, P=0.015; r=–0.343, P=0.001). The errors ofobject recognition memory negatively correlated to the sleep efficiency (r=–0.277, P=0.047), and positively correlated to the duration of wake time (r=0.304, P=0.001).Conclusion: The sleep quality decreased in the patients with PI, including the totalsleep time reduced, the sleep latency prolonged, the sleep efficiency decreased, REMduration and its proportion reduced, and N3duration and its proportion reduced. Thedegree of impairment in Psy-I group was the same as the PI group, but there was onlySWS and REMS decreased in Para-I. Spatial work memory impaired in the PI patients,and the impaired severity was similar between two PI subtypes. Spatial workingmemory consolidation is likely to be involved in SWS and REMS stages.