Abstract

Background: The aim of this study is to investigate the frequency of rapid eye movement (REM) sleep behavior disorder (RBD) in Parkinson's disease patients who presented to the movement disorders outpatient clinic and were classified as having benign or malignant phenotypes according to clinical criteria, and to examine the relationship of this condition with motor complications and non-motor symptoms.

Materials and Methods: In this cross-sectional study, the medical records of patients diagnosed with Parkinson's disease according to the UK Brain Bank diagnostic criteria at a tertiary training and research hospital were reviewed. Patients were divided into two groups as benign (bPD) and malignant (mPD) phenotypes, based on their disease course and clinical characteristics. Demographic data, Hoehn and Yahr stages, Mini-Mental State Examination (MMSE) scores, Schwab and England activities of daily living scores, and levodopa equivalent daily doses of the included patients were recorded. The presence of RBD was evaluated using physician file records and the IRBD-9 (The Innsbruck REM Sleep Behavior Disorder Diagnostic Inventory) questionnaire administered to patients/relatives via telephone.

Results: A total of 73 patients (36 bPD, 37 mPD) who met the inclusion criteria were included in the study. The mean age of the patients in the malignant group (78.2±6.3 years) was significantly higher compared to the benign group (69.3±7.6 years) (p < 0.001). The frequency of RBD was 62.1% in malignant patients, whereas it was 36.1% in benign patients; this difference between the groups was statistically significant (p = 0.036). Additionally, MMSE scores indicating cognitive functions were significantly lower (p < 0.001), and complaints of constipation, an autonomic symptom, were observed more frequently (p = 0.032) in the malignant group. In the logistic regression analysis, advanced age and the presence of clinical RBD were identified as independent risk factors predicting a malignant course.

Conclusion: The findings reveal that RBD is not merely an isolated accompanying non-motor symptom in Parkinson's disease; rather, it is a strong and independent clinical marker predicting the evolution of the disease into an aggressive malignant phenotype. Screening for the presence of RBD in routine evaluations is of critical importance for the early identification of patients at risk for cognitive decline and rapid clinical deterioration.