LRRK2 and REM sleep behavior disorder: Furthermore, for instance, the presence or absence of sleep disorder was reported in only 3.7% of cases, making it challenging to conclude whether rapid eye movement sleep behavior disorder (RBD) - increasingly recognized to be a predictor of poorer prognosis in PD80 - is less common in PARK-LRRK2 compared to idiopathic PD, as suggested by some authors51,81.