Living with Duchenne muscular dystrophy in Sweden - A national study of health status, respiratory care, life expectancy and causes of death

Abstract

Background: Duchenne muscular dystrophy (DMD) is a progressive neuromuscular disease characterized by severe morbidity and mortality. With improved health care, life expectancy has increased from late adolescence to a lifespan over 30 years of age, providing new challenges to understand and consider in the management and care of individuals living with DMD. Aims: To describe the epidemiology, life expectancy and causes of death among individuals with DMD in Sweden born since 1970, and to describe respiratory-related comorbidities and treatments, their correlation with longevity and cause of death, and their impacts on quality of life. Methods: Paper I is an epidemiological and nationwide descriptive study exploring the incidence, prevalence, life expectancy and causes of death. Paper II is a nationwide descriptive and case-control study exploring respiratory-related comorbidities including scoliosis, and treatment among Swedish patients with DMD and the impacts on longevity and cause of death. Paper III comprises a cross-sectional survey and a longitudinal sub-study aiming to characterise and identify associations between functional ability, ventilatory support and health-related quality of life among Swedish adult males with DMD. This paper includes an in-depth evaluation of motor functioning, lung functioning, respiratory comorbidity and other comorbidities over time. Paper IV is a cross-sectional survey exploring perceived quality of life among adult men with DMD and explore its associations with lung function and patient-reported symptoms including fatigue, poor quality of sleep, depressive symptoms and pain. Results: In paper I, 373 males with DMD were identified, among which 129 were deceased. Median survival was 29.9 years, with cardiac or respiratory failure being the leading causes of death in 79.9% of patients. The patients who died from non-cardiopulmonary causes died at younger ages than the patients with cardiopulmonary causes of death. Paper II showed that pneumonia was commonly found in patients with DMD. Pneumonia and scoliosis untreated by surgery are two risk factors that increased the risk of dying from respiratory-related causes. Paper III showed that despite the progressive functional decline during early adulthood, that adult men with DMD rated their overall health-related quality of life as relatively good. The study also revealed that none of age, functional ability, lung function and level of use of assisted ventilation were associated with overall health-related quality of life. Paper IV suggested that overall quality of life appeared to be good in adult men with DMD, although differences were evident across the domains of QoL. Further associations between QoL and patient-reported outcomes were explored, including fatigue, poor sleep quality, depressive symptoms and pain. Lung function did not seem to affect these outcomes, irrespective of the use of assisted ventilation. Conclusions: Life expectancy for individuals with DMD is increasing at a national level, with cardiac failure being the leading cause of death; however, non-cardiopulmonary causes contribute to higher mortality among younger patients. The risk of developing pneumonia is high for patients living with DMD and entails a high risk of severe clinical outcomes, including early death. Adult men living with DMD appear to perceive their health as relatively good, while respiratory dysfunction seems to have limited influence on subjective disease-associated symptoms.