Frequency of Suicidal Ideation and Associations With Autonomic, Motor, and Cognitive Dysfunction in People With REM Sleep Behavior Disorders

Background and ObjectivesREM sleep behavior disorder (RBD) is characterized by loss of REM sleep atonia leading to dream enactment behavior. Isolated RBD (iRBD) is a known prodrome of alpha-synuclein pathology including Parkinson disease (PD) and dementia with Lewy bodies (DLB). Depression is also a common prodromal symptom of PD/DLB, and death by suicide is greater among individuals with PD. Patients with RBD are at greater risk of comorbid depression, but the prevalence of suicidal ideation in this population is unknown. We aim to assess the frequency of suicidal ideation and whether it is associated with autonomic, motor, and cognitive dysfunction in the North American Prodromal Synucleinopathy 2 (NAPS2) consortium. MethodsNAPS2 is a longitudinal study that includes measurements of autonomic function (SCOPA-AUT, orthostatic blood pressure), motor function (UPDRS), cognition (MoCA), and suicidal ideation (PHQ-9). We used a linear mixed-effects model, adjusting for age, sex, impulsivity, current carbidopa/levodopa use, and PHQ-9 score, to compare those who endorsed recent suicidal ideation with those who did not. ResultsOf 489 total participants, 40 endorsed suicidal ideation at the first visit (22.5% female, mean age 61.5) and 449 denied suicidal ideation (19.4% female, mean age 64.6). Higher PHQ-9 scores were significantly associated with higher SCOPA-AUT scores (+0.566; SE = 0.045; p < 2 × 10−16), higher UPDRS II scores (+0.372; SE = 0.03; p < 2 × 10−16), higher UPDRS III scores (+0.265; SE = 0.057; p = 3.80 × 10−6), and lower MoCA scores (−0.078; SE = 0.021; p = 3 × 10-4). The PHQ-9 score was not significantly associated with orthostatic blood pressure drops. DiscussionRecent suicidal ideation occurred in approximately 1 of 12 patients with iRBD, a prodromal syndrome of PD with an increased risk of death by suicide. Individuals with iRBD who scored higher on PHQ-9 had on average greater autonomic dysfunction on SCOPA-AUT, more motor findings, and greater cognitive deficits. This study establishes that suicidal ideation is common in iRBD and suggests an iRBD phenotype that identifies individuals at high risk of depression and suicide. Future studies should expand on these findings and target interventions to decrease mortality and self-harm.