0683 Rest-activity Pattern in Isolated RBD – from Prodromal Stage to Association with Parkinsonism-first Phenoconversion

Abstract

Introduction: Previous evidence suggested that the alteration of rest-activity pattern occurred in patients with isolated rapid eye movement behavior disorder (iRBD), a prodromal stage of alpha-synucleinopathy with implication to future phenoconversion. Nonetheless, it remains unclear whether this rest-activity pattern alteration has already emerged in the prodromal stage of RBD, and whether it would be related to conversion of iRBD into parkinsonism-first or dementia-first subtype of alpha-synucleinopathy. Method(s): We performed 1) a case-control study to compare the rest-activity pattern measured by 7-day actigraphy among prodromal RBD subjects (n = 21) and their age-, sex-, and body mass index-matched control subjects (n = 52) and patients with iRBD (n = 63); and 2) a longitudinally follow-up study to investigate the predictive value of altered rest-activity pattern to parkinsonism-first or dementia-first subtype of alpha-synucleinopathy in full sample of patients with iRBD (n = 170). Prodromal RBD subjects were defined as subjects who had recurrent dream-enactment behaviors but with subthreshold REM sleep electromyography activity. Generalized linear model was employed to assess rest-activity pattern in prodromal RBD subjects and competing risk regression model was used to determine the predictive value of rest-activity pattern to RBD phenoconversion. Result(s): Similar to patients with iRBD, prodromal RBD subjects had more daytime probable napping (percentage and duration) and lower average weekly activity level and physical activity level during active period as compared to control subjects. Of 170 patients with iRBD, 166 were successfully followed up with a mean follow-up duration of 4.6 years. Lower average weekly activity level, amplitude, and physical activity level during active period were associated with a higher risk of parkinsonism-first subtype of alpha-synucleinopathy, instead of dementia-first subtype. Conclusion(s): Our study found that altered rest-activity pattern has already emerged in prodromal stage of RBD. As for iRBD patients, lower physical activity level and amplitude might serve as predictive markers of parkinsonism-first conversion.