Assessment of respiratory function and need for non-invasive ventilation in a cohort of patients with myotonic dystrophy type 1 followed at one single expert centre

Introduction Respiratory insufficiency is one of the main causes of death in myotonic dystrophy type 1 (DM1). Although there is general consensus these patients have a restrictive ventilatory pattern, hypoventilation, chronic hypercapnia and sleep disturbances, the prevalence of respiratory disease and indication for and effects of non-invasive ventilation (NIV) need to be further explored. Objectives We aim to describe the respiratory function and the need for NIV at baseline and over time in a cohort of adult patients with DM1. Methods One hundred and fifty-one adult patients with DM1 were subjected to arterial blood gas analysis, sitting and supine forced vital capacity (FVC), peak cough expiratory flow (PCEF), nocturnal oximetry, maximal inspiratory and expiratory pressures (MIP/PEP). Results On first assessment 84 of 151 had normal respiratory function (median age 38 years, median BMI 23.9, median disease duration: 11 years); 67 received an indication to use NIV (median age: 49 years, median BMI: 25,8, median disease duration: 14 years). After a median time of 3.85 years, 43 patients were lost to follow-up; 9 of 84 required NIV; only 17 of 67 with the new NIV prescription were adherent. Conclusions We provide additional data on the natural history of respiratory function decline and treatment adherence in a relatively large cohort of well-characterized patients with DM1. A high proportion (28%) were lost to follow-up. A minority (11%) required NIV, and only 25% were treatment adherent, irrespective of specific demographics and respiratory features. Our results also confirm previous findings showing that age, disease duration and higher BMIs are predisposing factors for respiratory impairment.