Cognitive abnormalities were investigated in Chinese patients with iRBD.

MoCA could detect cognitive abnormalities and serve as a screening scale.

The iRBD patients performed poorly on verbal memory tests.

The visual memory and visuospatial abilities were impaired, although no difference was found after Bonferroni correction.

Cognitive deficits were an early clinical marker in the prodromal stage of synucleinopathy.