Prevalence and clinical correlates of sleep disordered breathing in myotonic dystrophy types 1 and 2.

PURPOSE: Myotonic dystrophy types 1 (DM1) and 2 (DM2) are the most common muscular dystrophies in adulthood. A high prevalence of excessive daytime sleepiness (EDS) and sleep disordered breathing was documented in DM1; however, there are limited data available regarding DM2. Goals of the study were: (1) to evaluate the prevalence of sleep apnea in a large cohort of patients (71 DM1 and 14 DM2) and (2) to analyze correlations among such disorders and clinical features of myotonic dystrophies.

METHODS: All patients underwent clinical examination, subjective sleep evaluation, and home based cardiorespiratory monitoring, and most of them performed pulmonary function tests and oropharyngeal-oesophageal scintigraphy (OPES).

RESULTS: Almost 45% of patients reported poor sleep quality; only 20% of them referred EDS. Sleep studies documented sleep apnea, mostly obstructive, in 69% DM1 patients and 43% DM2 patients; overall, 28% of cases needed non-invasive ventilation. Neither age, gender, illness duration, body mass index, muscle involvement, OPES respiratory function indexes, nor n(CTG) in leukocytes were predictive of sleep apnea in DM1 patients. Conversely, in DM1 the central apnea-hypopnea index is correlated with the oral transit time estimated by OPES, whereas in DM2 apnea indexes are correlated with pulmonary function parameters.

CONCLUSIONS: Sleep apnea is highly prevalent in both forms of myotonic dystrophies. In DM1, no clinical parameters appear to be predictive, while age appears to influence the severity of the obstructive variant; in DM2, the severity of sleep apnea is correlated with the degree of respiratory muscle involvement. Considering the harmful consequences of sleep apnea on cardiorespiratory function, our findings suggest including PSG in the follow-up of myotonic dystrophies.