title: Age at onset of first signs or symptoms predicts age at loss of ambulation in Duchenne and Becker Muscular Dystrophy: Data from the MD STARnet.
abstract: OBJECTIVE
  We investigated the prognostic utility of onset age at first signs and symptoms (SS) to predict onset age at loss of ambulation (LOA) for childhood-onset Duchenne and Becker Muscular Dystrophies (DBMD).
  
  
  METHODS
  Our cohort comprised male cases with DBMD ascertained by the population-based Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet). Adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards models for associations between onset ages of first SS and LOA. Covariates controlled for were corticosteroid use, family history of DBMD, birth year, race/ethnicity, and MD STARnet site. Onset age at first SS was considered as a continuous and as a categorical variable.
  
  
  RESULTS
  A one-year increase in onset age at first SS was significantly associated with a 10% reduction in annual risk of LOA (HR = 0.90, CI = 0.87-0.94). Treating onset age at first SS as a categorical variable yielded a similar association (≥ 5 years: referent; ≥ 3 to < 5 years: HR = 1.36, CI = 1.02-1.81; 18 months to < 3 years: HR = 1.72, CI = 1.31-2.26; < 18 months: HR = 1.52, CI = 1.14-2.02).
  
  
  CONCLUSIONS
  Earlier onset age at first SS is associated with earlier onset age at LOA and may have clinical utility in differentiating childhood-onset Duchenne and Becker muscular dystrophies.
authors.affiliation: University of Rochester, Rochester, NY, USA.
authors.forename: Emma
authors.initials: E
authors.lastname: Ciafaloni
authors.affiliation: New York State Department of Health, Albany, NY, USA.
authors.forename: Anil
authors.initials: A
authors.lastname: Kumar
authors.affiliation: The University of Iowa, Iowa City, IA, USA.
authors.forename: Ke
authors.initials: K
authors.lastname: Liu
authors.affiliation: University of Rochester, Rochester, NY, USA.
authors.forename: Shree
authors.initials: S
authors.lastname: Pandya
authors.affiliation: New York State Department of Health, Albany, NY, USA.
authors.forename: Christina
authors.initials: C
authors.lastname: Westfield
authors.affiliation: New York State Department of Health, Albany, NY, USA.
authors.forename: Deborah J
authors.initials: DJ
authors.lastname: Fox
authors.affiliation: The University of Iowa, Iowa City, IA, USA.
authors.forename: Kristin M
authors.initials: KM
authors.lastname: Caspers Conway
authors.affiliation: Weill Cornell Medical, New York, NY, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Cunniff
authors.affiliation: The University of Iowa, Iowa City, IA, USA.
authors.forename: Katherine
authors.initials: K
authors.lastname: Mathews
authors.affiliation: Colorado School of Public Health, Aurora, CO, USA.
authors.forename: Nancy
authors.initials: N
authors.lastname: West
authors.affiliation: The University of Iowa, Iowa City, IA, USA.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Romitti
authors.affiliation: University of Rochester, Rochester, NY, USA.
authors.forename: Michael P
authors.initials: MP
authors.lastname: McDermott
mesh_terms: D017668:Age of Onset; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D020233:Gait Disorders, Neurologic / Q000209:etiology* / Q000503:physiopathology; D006801:Humans; D007223:Infant; D008297:Male; D020388:Muscular Dystrophy, Duchenne / Q000150:complications* / Q000503:physiopathology; D011159:Population Surveillance / Q000379:methods*; D016016:Proportional Hazards Models
keywords: Becker Muscular Dystrophy; Duchenne Muscular Dystrophy; ambulation