Discrepancies of Cognition Among Different Subtypes and Correlations with Sleep Parameters in the Patients with Chronic Insomnia DisorderAuthor(s): Lan Xia, Gui-Hai Chen, Qi-Guo Wei, Yi-Jun Ge, Xiao-Yi Kong, Xue-Yan Li, Ping Zhang
Backgrounds: Insomniacs have damaged memory. We intended to explore the differ encesof memory and po lysomnogram sleep parameters in the patients with different subtypes ofchronic insomnia disorder (CID) and the correlations between them.
Methods and Findings: 106 CID outpatients were divided into difficulty initiating sleep (DIS),early m orning awakening (EMA), difficulty maintaining sleep (DMS) and mix sleep difficulty(MSD) groups. The polysomnography was completed during a night. Nine-Boxes MazeTest was used to assess the spatial/object working memories (SWM, OWM), spatial/objectreference memories (SRM, ORM) and object recognition memory (ORcM). The results showed
that compared to the DMS group, the EMA group had more SWM e r rors, and the MSD groupad d i t ionally had more ORcM errors. Relative to the DMS group, the EMA and MSD groups hadlower sleep efficiency, longer wake time after sleep onset, decreased REM% and increasedN1%. Furthermore, the EMA group had longer REM latency and less REM density, the MSDgroup had shorter REM time, and the DIS group had enhanced N1%. For all the insomniacs,the linear regression analysis showed that a negative effect of sleep parameters on cognitionmeasures existed in pairs as following: N2% vs. ORM errors; REM%/N3%/ REM density vs. SRMerrors; REM%/N2% vs. SWM errors; N3% vs. ORcM. The canonical correlation analysis showedthat SWM errors negatively correlated with REM, N2% and N3%.
Conclusions: The insomnia-related memory impairment was different among th e subtypes inthe CID patients, with the worst memory in the EMA and MSD subtypes. The decreased N2%,N3% and REM% might be associated with damaged spatial memory.