Restless legs syndrome and daytime sleepiness are prominent in myotonic dystrophy type 2.

Objectives: Although sleep disturbances are common in myotonic dystrophy type 1 (DM1), sleep disturbances in myotonic dystrophy type 2 (DM2) have not been well-characterized. We aimed to determine the frequency of sleep disturbances in DM2.
Methods: We conducted a case-control study of 54 genetically confirmed DM2 subjects and 104 medical controls without DM1 or DM2, and surveyed common sleep disturbances, including symptoms of probable restless legs syndrome (RLS), excessive daytime sleepiness (EDS), sleep quality, fatigue, obstructive sleep apnea (OSA), probable REM sleep behavior disorder (pRBD), and pain. Thirty patients with DM2 and 43 controls responded to the survey. Group comparisons with parametric statistical tests and multiple linear and logistic regression analyses were conducted for the dependent variables of EDS and poor sleep quality.
Results: The mean ages of patients with DM2 and controls were 63.8 and 64.5 years, respectively. Significant sleep disturbances in patients with DM2 compared to controls included probable RLS (60.0% vs 14.0%, p < 0.0001), EDS (p < 0.001), sleep quality (p = 0.02), and fatigue (p < 0.0001). EDS and fatigue symptoms were independently associated with DM2 diagnosis (p < 0.01) after controlling for age, sex, RLS, and pain scores. There were no group differences in OSA (p = 0.87) or pRBD (p = 0.12) scores.
Conclusions: RLS, EDS, and fatigue are frequent sleep disturbances in patients with DM2, while OSA and pRBD symptoms are not. EDS was independently associated with DM2 diagnosis, suggesting possible primary CNS hypersomnia mechanisms. Further studies utilizing objective sleep measures are needed to better characterize sleep comorbidities in DM2.