The Relationships Between Ruminative Thinking And Rapid Eye Movement Sleep And Cognition In Patients With Chronic Insomnia

Background and objective: Increased ruminating thinking in patients with chronic insomnia（CID）leads to selective increased attention to sleep-related threats.This may lead to physiological hyperarousal and impair daytime cognition and other functions in patients.Ruminative thinking is thought to be associated with REMS as the most common cognitive-emotional arousal.However,previous studies have only found ruminant thinking to be associated with indicators of sleep continuity.This is partly due to the fact that past studies only used macroscopic EEG data and not more fine-grained EEG research methods such as spectral analysis;on the other hand,it may be due to the neglect of REMS heterogeneity.Although some preliminary studies have shown that REMS can be divided into emotion-related temporal REMS and tension REMS characterized by high arousal,the characteristics of different types of REMS in CID patients have not been reported.The purpose of this study was to assess the relationship between ruminative thinking and different types of REMS and cognitive function in patients with insomnia.Methods: Thirty-one patients with chronic insomnia disorder（CID）and 27 age-and gender-matched healthy controls（HC）were included.Subjects’ ruminative thinking was assessed using the Immersion-Reflection Questionnaire;emotional and cognitive functioning was assessed using the Hamilton Depression Inventory（HAMD）,Hamilton Anxiety Inventory（HAMA）,and Montreal Cognitive Inventory（Mo CA-C）;sleep quality was assessed using the Pittsburgh Sleep Quality Index（PSQI）;non-rapid eye movement sleep（NREM）and different types of sleep were assessed using polysomnography REMS structural features.Results: There was no statistical difference in age and gender between the CID and HC groups（P > 0.05）.PSQI,HAMD,and HDMA were higher in CID patients compared to HC（Ps<0.05）.Compared to HC,patients with CID had longer sleep latency,shorter total sleep time,lower sleep efficiency,poorer sleep continuity(longer awakening time,shorter REM phase time,shorter N1 phase,lower percentage of N3 and N3,lower percentage of phasic REM and phasic REM to total sleep time,lower percentage of phasic REM,and higher percentage of tonic REM（Ps<0.05）.In addition,CID patients had lower δ power,higher α power and β power in N1,higher α power in N2,higher β power in N3,higherβ power in REM,higher β power and σ power in phasic REM,and higher β power and γpower in tense REM（Ps<0.05）.Compared to HC,CID patients had lower Mo CA-C total scores as well as lower scores for executive function,naming,attention and language factors（Ps<0.05）,and no significant differences were seen for abstraction,memory and orientation scores（Ps>0.05）.Compared to HC,ruminant thinking scores were higher in CID patients.In patients with CID,ruminative thinking was not associated with PSQI scores,was negatively correlated with total sleep time and sleep efficiency（r=-0.500,P<0.05;r=-0.454,P<0.05）,and was positively correlated with sleep latency and wakefulness duration（r=0.481,P<0.01;r=0.475,P<0.05）,and was associated with phasic REM period and the percentage of phasic REM periods were negatively correlated（r=-0.459,P<0.01;r=-0.355,P<0.05）.In addition,ruminative thinking in CID patients was negatively correlated with N1 and N2 θ（r=-0.375,P<0.05;r=-0.437,P<0.05）and positively correlated with N3 and PR β power（r=-0.385,P<0.05;r=-0.401,P<0.05）.In cognitive function,ruminative thinking was negatively correlated with attentional function in patients with CID（r=-0.409,P<0.05）.Conclusion: There is a relationship between ruminative thinking and phasic rapid eye movement sleep and cognitive impairment in patients with CID.In addition,total REM sleep was reduced in patients with CID,while tonic REM was relatively increased.