Cognitive study on Chinese patients with idiopathic REM sleep behavior disorder

We investigated cognitive abnormalities using standard tests in Chinese patients with idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD) compared with those in normal controls.

Twenty-three patients with iRBD and 23 normal controls were included in this study. All of the participants underwent one night of video-polysomnography (PSG) monitoring to certify REM sleep without atonia or abnormal behaviors. The cognitive assessments were administered and scored according to a standard procedure, including global cognitive screening and attention/processing speed, executive function, memory, language, and visuospatial ability testing.

Patients with iRBD had similar scores of the Mini Mental State Examination (MMSE) but lower Montreal Cognitive Assessment (MoCA) scores compared with controls (p>0.05, p=0.013). The iRBD patients performed poorly on verbal memory tests, which included immediate recall (p<0.001), delayed recall (p<0.001), and false recognitions (p=0.002) of the Rey Auditory Verbal Learning Test (RAVLT). The visual memory and visuospatial abilities were also impaired in iRBD patients, as reflected by the copy (p=0.005) and immediate (p=0.004) and delayed (p=0.003) recall of the Rey-Osterrieth complex figure, although no difference was found after Bonferroni correction. The duration of RBD was 6.98±8.10years. After controlling for age, the duration of RBD was only correlated with the Trail Making Test B (r=0.613, p=0.045) and block design (r=-0.667, p=0.025).

Impaired verbal memory was observed in iRBD patients who identified as Chinese. MoCA could detect cognitive abnormalities and serve as a screening scale. The present study further confirmed cognitive deficits in iRBD as an early clinical marker in the prodromal stage of synucleinopathy.