Mortality Trends and Causes of Death in Myotonic Dystrophy Type 1 Patients From the UK Clinical Practice Research Datalink.

Introduction/aim: Patients with myotonic dystrophy type1 (DM1) have reduced lifespan. This study aimed to quantify mortality risks, and evaluate causes and time trends in DM1.

Methods: We identified 1021 DM1 patients and 15,104 matched DM1-free controls from the United Kingdom (UK) Clinical Practice Research Datalink. We used Cox proportional hazards regression models to assess differences in all-cause or cause-specific mortality between DM1 patients and matched controls, and computed standardized mortality ratios (SMRs) for comparisons of DM1 patients with the UK general population.

Results: DM1 patients were at higher risk of death compared with matched DM1-free controls (hazard ratio [HR] = 2.9, 95% confidence interval [CI] = 2.5-3.4) or the general UK population (SMR = 8.1, 95% CI = 7.3-9.1). The excess risk was primarily attributed to deaths from respiratory failure (HR = 26.7, p < 0.001), aspiration pneumonia (HR = 15.8, p < 0.001), arrythmia, and conduction defects (HR = 15.7, p < 0.001). No mortality risk difference between DM1 patients and matched DM1-free cohort was noted for all cancers combined (p = 0.52). No significant calendar time-related changes in overall survival were seen for DM1 patients (p trend = 0.19). In mortality cause-specific analysis, and compared with patients diagnosed before 1993, death from cancer was on the rise (HR = 2.35, and 5.82 for patients diagnosed 1993-2003, and 2004-2016).

Discussion: Most DM1 patients died of known disease complications. This highlights the need for integrated clinical approaches with more careful and frequent monitoring.