¹Chang Gung Memorial Hospital and College of Medicine, Department of Psychiatry and Sleep Center, Taoyuan, Taiwan, ²Chang Gung Memorial Hospital, Chang Gung Memorial Hospital, Taoyuan, Taiwan

Background: As the proportion of elderly increases, age-related psychological and physical health issues have gradually been taken seriously, especially depression and neurodegenerative disorders, which are also closely related to sleep. Depressive individuals often report sleep disturbances, and depression can lead to a decline in executive functions, with inhibitory control being the most severely affected. This decline is partly due to the inability to suppress negative rumination and worry, leading to the development of depressive symptoms. Additionally, executive function is also easily affected by sleep deprivation. However, the actual association between depression, sleep, and executive function requires further discussion.

Aims & Objectives: Therefore, this study focuses on the elderly population to investigate the interconnections between sleep, depression, and neurocognitive function.

Method: This study included elderly subjects ages 65 and above, with 35 in the depression group and 44 in the non-depression group. After obtaining informed consent and ensuring that participants met the cutoff score on the Montreal Cognitive Assessment (MoCA) screening, they sequentially filled out basic demographic information, the Geriatric Depression Scale (GDS-15), the Insomnia Severity Index (ISI), the Pittsburgh Sleep Quality Index (PSQI), the Activities of Daily Living (ADLs) scale, and the Instrumental Activities of Daily Living (IADLs) scale. They also completed the Conners' Continuous Performance Test (CPT), and wore an actigraphy for one week. The data will be analyzed using statistical methods such as descriptive statistics, correlation analysis, and bootstrapping.

Results: 79 participants were included (29 men and 50 women; mean age: 73.02±5.85 years). The elderly depression group showed significantly poorer global cognitive function, specific sleep quality indicators, and executive function compared to the non-depressed group. There were correlations between depression, specific sleep quality indicators, and specific components of executive function. Total in-bed time and total sleep time were found to mediate the relationship between elderly depression and global cognitive function. This study also examined the relationship between the severity of elderly depression and inhibitory control. The findings indicated that sleep quality did not mediate the relationship between depression severity and inhibitory control. However, the severity of elderly depression could directly predict certain inhibitory control indicators.

Discussion & Conclusions: This study found that elderly individuals with depression exhibit impairments in global cognitive function, specific sleep quality indicators, and executive function. Depression affects global cognitive function through total time in bed and total sleep time, indicating that sleep duration plays a crucial role in the relationship between elderly depression and global cognitive function.