The prospective memory of patients with idiopathic REM sleep behavior disorder

Background: Idiopathic rapid eye movement sleep behavior disorder (iRBD) likely represents the prodromal stage of synucleinopathy. The present study was to investigate if there was prospective memory (PM) impairment and the relationship between different PM tasks and traditional cognitive tests in patients with iRBD.

Methods: A total of 28 patients with iRBD, 25 with Parkinson's disease (PD) and 21 healthy controls were included. The Cambridge Prospective Memory Test (CAMPROMPT) was used to measure the PM including time-based (TBPM) and event-based PM (EBPM). Standard cognitive tests were administered to all participants.

Results: EBPM scores were lower only in patients with iRBD, while the obvious PM abnormalities were found in patients with PD. The patients with iRBD and PD performed worse on delayed recall of the Rey Auditory Verbal Learning Test (RAVLT) and copy of the Rey-Osterrieth complex figure (ROCF). The EBPM correlated with attention, executive function, and immediate memory besides working memory in patients with iRBD. The PM tasks involved in more memory functions in PD patients.

Conclusions: The patients with iRBD were impaired on both episodic memory and EBPM tasks that correlated with attention, executive function, and immediate memory. The PM abnormality was an early cognitive change in iRBD to which more attention should be paid more attention.