Associations between timing of corticosteroid treatment initiation and clinical outcomes in Duchenne muscular dystrophy

The long-term efficacy of corticosteroid treatment and timing of treatment initiation among Duchenne muscular dystrophy (DMD) patients is not well-understood. We used data from a longitudinal, population-based DMD surveillance program to examine associations between timing of treatment initiation (early childhood [before or at age 5 years], late childhood [after age 5 years], and naïve [not treated]) and five clinical outcomes (age at loss of ambulation; ages at onset of cardiomyopathy, scoliosis, and first fracture; and pulmonary function). Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using survival analysis. DMD patients who initiated corticosteroid treatment in early childhood had a higher risk of earlier onset cardiomyopathy compared to cases who initiated treatment in late childhood (HR = 2.0, 95% CI = [1.2, 3.4]) or treatment naïve patients (HR = 1.9, 95% CI = [1.1, 3.2]), and higher risk of suffering a fracture (HR = 2.3, 95% CI = [1.4, 3.7] and HR = 2.6, 95% CI = [1.6, 4.2], respectively). Patients with early childhood treatment had slightly decreased respiratory function compared with those with late childhood treatment. Ages at loss of ambulation or scoliosis diagnosis did not differ statistically among treatment groups. We caution that the results from our study are subject to several limitations, as they were based on data abstracted from medical records. Further investigations using improved reporting of disease onset and outcomes are warranted to obtain a more definitive assessment of the association between the timing of corticosteroid treatment and disease severity.