Serum p‐tau217 Is a Prognostic Indicator of Cognitive Impairment in Idiopathic REM Sleep Behavior Disorder

Assess the performance of serum phosphorylated tau 217 (p-tau217) and neurofilament light chain (NfL) in predicting risk of cognitive impairment or phenoconversion to dementia in individuals with iRBD.We measured serum p-tau217 and NfL levels by electrochemiluminescence across 4 polysomnographically confirmed iRBD cohorts (n = 300), including individuals who phenoconverted to Parkinson's disease (PD) (n = 51), dementia with Lewy bodies (DLB) (n = 22), and multiple system atrophy (MSA) (n = 5).Serum p-tau217 levels were increased in individuals with iRBD and cognitive impairment (CI) on testing defined as Montreal Cognitive Assessment