Changed serum levels of neurotrophic factors and their correlations with sleep and cognition in patients with chronic insomnia disorder

Abstract

Objective To explore serum levels of brain-derived neurotrophic factor (BDNF) and glial-derived neurotrophic factor (GDNF), and whether changes of BDNF and GDNF are correlated with sleep quality and cognitive function in patients with chronic insomnia disorder (CID). Methods Fifty-seven CID patients in the Department of Sleep Disorders, Chaohu Hospital of Anhui Medical University and 30 healthy controls were enrolled from May 2017 to July 2018. Pittsburgh Sleep Quality Index (PSQI) was used to assess the degree of insomnia severity (some CID patients were monitored by overnight polysomnography). Montreal Cognitive Assessment (MoCA) scale and Nine-Box Maze were used to assess general cognitive function and specific memory function, respectively. The serum levels of BDNF and GDNF were detected using ELISA. Results Compared to the controls, CID patients had significantly higher PSQI scores (CID patients: 14.0±2.2, healthy controls: 3.9±1.1; t=28.093, P<0.01), lower MoCA scores (CID patients: 24.5±3.6, healthy controls: 26.5±0.9; t=-2.985, P<0.01), more errors in object working memory (CID patients: 1.0 (0, 1.0), healthy controls: 0 (0, 0.3)), spatial working memory (CID patients: 3.0 (2.0, 4.0), healthy controls: 1.0 (1.0, 2.0)) and object recognition memory (CID patients: 0 (0, 0), healthy controls: 0 (0, 0); Z=-2.896、-5.007、-2.306, P<0.05), and lower serum BDNF (CID patients: (19.48±7.50) ng/ml, healthy controls: (46.49±13.33) ng/ml; t=-10.274, P<0.01) and GDNF (CID patients: (32.76±14.04) pg/ml, healthy controls: (59.63±20.30) pg/ml; t=-7.240, P<0.01). The partial correlation analysis showed that in the CID patients, the levels of BDNF and GDNF were correlated with PSQI scores negatively (r=-0.293, -0.320, P<0.05) and MoCA scores positively (r=0.331, 0.295, P<0.05). The BDNF level was also correlated with the duration of disease and the errors in the spatial working memory test negatively (r=-0.319, -0.393, P<0.05), and the GDNF level was correlated with the total sleep time detected with polysomnogram positively (r=0.520, P<0.05). Conclusion Serum BDNF and GDNF levels in CID patients were lower than those in healthy controls, and correlated with sleep quality and cognitive impairment. Key words: Insomnia; Neurotrophic factor; Cognitive function