Diagnostic Criteria for REM Sleep Behavior Disorder

Participants were selected from 12 centers of the International REM Sleep Behavior Disorder Study Group and were recruited from 2008 to 2011. All RBD patients had RBD diagnosis confirmed by polysomnography according to the International Classification of Sleep Disorders-2⁷ ; namely, loss of REM atonia on polysomnographic trace in association with history of dream-enactment or witnessed dream enactment during REM sleep on video polysomnogram. Patients were not blinded to RBD diagnosis when they completed the questionnaire. Convenience sampling was used (i.e., maximal recruitment each center). All cases had neurological examination confirming the absence of dementia (defined as Mini-Mental State Examination [MMSE] <24 with functional impairment resulting from cognitive decline^{8 (link)}— note that MMSE was required only if symptoms of dementia were present) and parkinsonism (by UK Brain Bank criteria^{9 (link)}). Each center also recruited controls (both healthy subjects and patients with other sleep disorders), frequency-matched 1:1 on age (within 5 years) and sex (10% tolerance outside perfect matching allowed). All controls underwent a polysomnogram confirming the absence of RBD. Participants with asymptomatic REM atonia loss were not included. Ethics approval was obtained from the research ethics board of each participating center. All patients gave informed consent according to the Declaration of Helsinki.