Supplementary Material for: Duchenne and Becker Muscular Dystrophies’ Prevalence in MD STARnet Surveillance Sites: An Examination of Racial and Ethnic Differences

Introduction: Previous studies indicated variability in the prevalence of Duchenne and Becker muscular dystrophies (DBMD) by racial/ethnic groups. The Centers for Disease Control and Prevention’s (CDC) Muscular Dystrophy Surveillance, Tracking, and Research network (MD STARnet) conducts muscular dystrophy surveillance in multiple geographic areas of the USA and continues to enroll new cases. This provides an opportunity to continue investigating differences in DBMD prevalence by race and ethnicity and to compare the impact of using varying approaches for estimating prevalence. Objective: To estimate overall and race/ethnicity-specific prevalence of DBMD among males aged 5–9 years and compare the performance of three prevalence estimation methods. Methods: The overall and race/ethnicity-specific 5-year period prevalence rates were estimated with MD STARnet data using three methods. Method 1 used the median of 5-year prevalence, and methods 2 and 3 calculated prevalence directly with different birth cohorts. To compare prevalence between racial/ethnic groups, Poisson modeling was used to estimate prevalence ratios (PRs) with non-Hispanic (NH) whites as the referent group. Comparison between methods was also conducted. Results: In the final population-based sample of 1,164 DBMD males, the overall 5-year prevalence for DBMD among 5–9 years of age ranged from 1.92 to 2.48 per 10,000 males, 0.74–1.26 for NH blacks, 1.78–2.26 for NH whites, 2.24–4.02 for Hispanics, and 0.61–1.83 for NH American Indian or Alaska Native and Asian or Native Hawaiian or Pacific Islander (AIAN/API). The PRs for NH blacks/NH whites, Hispanics/NH whites, and NH AIAN/API/NH whites were 0.46 (95% CI: 0.36–0.59), 1.37 (1.17–1.61), and 0.61 (0.40–0.93), respectively. Conclusions: In males aged 5–9 years, compared to the prevalence of DBMD in NH whites, prevalence in NH blacks and NH AIAN/API was lower and higher in Hispanics. All methods produced similar prevalence estimates; however, method 1 produced narrower confidence intervals and method 2 produced fewer zero prevalence estimates than the other two methods.