1025 The Impact of Depression on Neurocognitive Functions and Conversion in Isolated REM Sleep Behavior Disorder

Abstract Introduction Depression is frequently observed in patients with isolated REM sleep behavior disorder (iRBD). The aim of this study was to analyze cognitive function and quantified electroencephalography (QEEG) in iRBD patients according to the presence of depression, and to evaluate the impact of depression on the conversion to neurodegenerative diseases. Methods A total of 90 individuals with iRBD were included in this study. They were followed for up to 9 years, and 21 of them were converted to Parkinson's disease or dementia. Phenoconversion was defined when a definitive diagnosis of parkinsonism by neurologists or any form of dementia by geriatric psychiatrists was established based on evident clinical symptoms. The diagnosis of depression (27 among 90 iRBD) was made based on the initial interview or taking antidepressant medication. Results The depressed group showed poor performance in the executive function (p= 0.029, Stroop color test) than the non-depressed group. The depressed group tended to have lower z-scores than the non-depressed group in global cognition, attention, memory, and frontal/executive domains. The QEEG results, the relative gamma power in the temporal and parietal region, relative high gamma power in the parietal region were significantly increased (p=0.049; p=0.032; p=0.008) in the depressed than the non-depressed group. The conversion was significantly increased in iRBD patients with depression than iRBD without depression (p=0.013). The depression in iRBD patients had 3.319 of hazard ratio (p=0.011) for the risk of conversion to neurodegenerative diseases. Conclusion Depressive symptoms in iRBD patients should be monitored as aggravating cognitive dysfunction and a risk factor for conversion. Support (if any)