OBJECTIVES: Duchenne muscular dystrophy (DMD) is characterized by severe, progressive muscle weakness and early mortality. Estimates of the timing of key clinical milestones in DMD exist from clinical cohorts but real-world data are scarce. This study characterized the occurrence of and age at key clinical outcomes among DMD patients in a closed population database.

METHODS: Longitudinal population-based single-payer physician, hospitalization, and pharmacy records from the Manitoba Population Research Data Repository were used. In the absence of specific DMD codes, algorithms/clinical expertise were applied to identify DMD males ≤30 years old during 1998-2020. The frequency and median (interquartile range [IQR]) age at first key clinical event was estimated from those experiencing the event. Events included scoliosis, severe respiratory outcomes (respiratory failure, tracheostomy), cardiomyopathy, and mortality.

RESULTS: Of 198 DMD patients, most (62.7%) were ≤7 years old at index; median (IQR) follow-up was 9.6 (9.0) years. Scoliosis was recorded among 18% (median [IQR] age, 12 [4] years); severe respiratory outcomes among 20% (at 14 [12] years); and cardiomyopathy among 32% (at 13 [19] years). During the follow-up, mortality was observed in 27 (13.6%) patients, with a median (IQR) age of 19 (14) years. Kaplan-Meier analysis revealed that >85% of the cohort remained alive at ≥20 years old.

CONCLUSIONS: In this assessment, the ages of first-recorded key clinical outcomes were consistent with published estimates. Population-based data on mortality are novel and complement recent estimates from Sweden. Strengths included the closed population nature of the data and decades of follow-up. Limitations include a non-specific DMD code for cohort identification; and small sample sizes at older ages affected estimates of median age at mortality (as most individuals were enrolled in mid-childhood and followed for at most 22 years). These estimates contribute to the understanding of the natural history of DMD.