Multiorgan Involvement and Mortality in Individuals With Adult-Onset Myotonic Dystrophy (DM1)-A Danish Register-Based...

Adult-onset myotonic dystrophy type 1 (DM1) is characterized by a diagnostic delay due to milder symptoms than the infantile and juvenile forms. Despite this, there is a risk of negative biopsychosocial consequences, particularly due to the cognitive impact. Individuals with adult-onset DM1 may receive less attention and have lower adherence to hospital follow-ups, which increases the risk of adverse events and early death. The aim of this study was to provide knowledge on the time of diagnosis, multiorgan involvement, and mortality in a national cohort of individuals with adult-onset DM1.

Data from individuals with DM1 were extracted from the Danish National Health and administrative registers in the period 1994-2022; each individual with DM1 was paired with 10 reference individuals from the general Danish population.

Analyses were based on 949 individuals with DM1 and 9427 controls. The median age at diagnosis was 43 years; 40% of individuals had a parent-child relationship. Respiratory insufficiency and cataracts were the most common involvements among individuals with DM1. The average age at death was 58 years; risk of mortality was 5.87 times higher than controls (p < 0.001) and individuals with DM1 and cardiovascular disease had a higher mortality rate compared to controls (HR: 2.63, CI: 2.14-3.23, p < 0.001). The risk of mortality tended to decline in the later years of the study period.

Despite adult-onset DM1 often being characterized as mild, comorbidities and an excess risk of death are major concerns. This calls for attention from health professionals to improve rehabilitation and survival for this population.