Prodromal Status of Rapid Eye Movement Sleep Behavior Disorder: Clinical Significance and Future Perspectives

Rapid eye movement (REM) sleep behavior disorder (RBD) is a prodromal stage for major neurodegenerative diseases, particularly α-synucleinopathies. Recently, the spectrum of RBD is expanding and its prodromal state has been recognized and categorized into isolated REM sleep without atonia and isolated dream-enacting behavior. Although unclear, prodromal RBD frequently occurs in the aged population, with a significantly high phenoconversion rate to RBD and an increased risk of developing neurodegenerative disorders. More active and structured general surveillance of this condition may contribute to the effective modulation of major neurodegenerative diseases. However, the clinical and polysomnographic profiles of prodromal RBD, methods for effective screening and diagnosis of prodromal RBD, and biomarkers for disease progression and phenoconversion must be investigated.