Patients with myotonic dystrophy (DM) have complex respiratory and neurological disease. Sleepiness is common. We describe a prospective cohort study of patients with DM and response to sleep treatments.
Methods DM patients with daytime sleepiness or symptoms of respiratory failure were referred to the Regional Sleep Centre. They were admitted overnight for sleep study and respiratory assessment. If there was central hypoventilation causing respiratory failure, or obstructive sleep apnoea (OSA), they were offered non-invasive ventilation (NIV) or continuous positive airway pressure (CPAP) respectively. People without sleep disordered breathing with daytime sleepiness were assessed for modafinil, an alerting drug.
Results From May 2011 to May 2015, 120 people with DM had investigations. Mean age was 47 (SD 13, range 18–74), mean BMI 28 kg/m2 (7, 16–53) and mean Epworth Sleepiness Score 13 (5, 2–24). Mean Muscular Impairment Rating Scale was 3.85 (0.7, 2–5).
Mean FEV1 was 70% predicted (SD 22), FVC 68% predicted (27), with a >15% supine fall in FVC in 18%. PI max, PE max or SNIP were below 50% predicted in 73% of people.
In this cohort, 32 people (27%) had raised CO2 >6.2 mmHg; NIV was trialled and provided at home in 29 (90% of those in whom it was indicated). Twelve people (37%) have continued this, 17 (53%) have returned it.
Twenty one people (18%) were found to have OSA and 19 commenced CPAP (90% of those in whom it was indicated). This was continued by seven people (33%) and returned by 12 (57%).
Thirty seven people (31%) found to have no evidence of significant sleep-disorderd breathing were assessed for modafinil. Twenty seven people (73% of those in whom this was indicated) attended clinic for this: 16 (43%) had good effect from modafinil and continue on it, 8 (22%) had no effect or intolerance; in three (8%) it was not prescribed.
Thirty people (25% of total cohort) had no sleep disordered breathing and required no further input.
Conclusions DM is a heterogeneous disorder, with varying BMI, sleepiness, muscular and respiratory impairment. Overall, only 35% of the total cohort gained benefit from CPAP, NIV or modafinil and continued with this therapy.