Correlation between Serum Levels of Sympathetic Nerve Activity Markers and Sleep Quality and Cognitive Function in Patients with Chronic Insomnia Disorder

Objectives: To explore the changes of the serum levels of copeptin and α-amylase and the correlations with sleep quality and cognition function in the patients with chronic insomnia disorder (CID). Methods: Fifty-seven CID patients and thirty healthy controls were enrolled continuously. Pittsburgh Sleep Quality Index (PSQI), polysomnography (PSG) and Pre-Sleep Arousal Scale (PSAS) were used to assess the insomnia severity and cognitive and somatic manifestations of arousal experienced at bedtime. Montreal Cognitive Assessment scale (MoCA) and Nine-Box Maze were used to respectively assess general cognition and memories. The serum levels of copeptin and α-amylase were detected using Enzyme-Linked ImmunoSorbent Assay. Results: Compared to the controls, the CID patients had increased PSQI and PSAS scores (Z=‒7.678 and ‒7.350; Ps<0.001), decreased MoCA score (t=‒4.625, P<0.001), increased numbers of errors in the object working, spatial working and object recognition (Z=‒2.099, ‒3.935 and ‒2.266; Ps<0.05) memories, and elevated serum levels of copeptin and α-amylase (t=5.414 and 5.597, P <0.001). In the CID patients，the level of copeptin positively correlated with PSQI and PSAS scores (r=0.338 and 0.316; Ps<0.05), and PSG sleep latency, wake time and N1% (r=0.324, 0.325 and 0.278, Ps<0.05), and negatively correlated with PSG N 2% (r=‒0.279, Ps<0.05). Alpha-amylase was positively correlated with waking numbers in PSG (r=0.293, P< 0.05). Multiple linear regression analysis showed that copeptin level affected PSQI score and PSG sleep latency (P<0.05). Conclusions: The serum levels of copeptin and α-amylase elevated in the CID patients, and the serum levels of copeptin may be associated with the poor sleep quality, especially in the individuals of initial sleep difficulties.