Sleep disorders in myotonic dystrophy type 2: A controlled polysomnographic study and self-reported questionnaires

Background: Scarce data are available regarding the occurrence of sleep disorders in Myotonic Dystrophy type 2(DM2).We investigated sleep-wake cycle and daytime sleepiness in DM2 patients compared with healthy subjects and DM1 patients. Patients and Methods: Twelve DM2 outpatients, twelve age- and sex-matched healthy controls and 18 DM1 patients were evaluated. Subjective quality of sleep was assessed by means of the Pittsburgh Sleep Quality Index (PSQI). Both the Epworth Sleepiness Scale and the Daytime Sleepiness Scale were performed in order to evaluate excessive daytime sleepiness (EDS). All participants underwent a 48-hour polysomnographic monitoring and the Multiple Sleep Latency Test.Results: Sleep efficiency was <90% in 12/12 DM2 patients, and significantly reduced when compared with controls or with DM1. Decreased sleep efficiency was associated with sleep-disordered breathing in 7/12 DM2 patients and/or PLMS in 3/8 patients. Six DM2 patients showed REM sleep without atonia, whereas none of controls and DM1 patients showed REM sleep dysregulation. The global PSQI score was higher in DM2 versus controls and versus DM1. Conclusions: Sleep quality in DM2 is poorer than in DM1 and controls. Sleep apnea is the most common sleep disorder in DM2. OSA and sleep fragmentation may represent the main cause of EDS, whereas PLMS are a frequent finding in DM1.