Equity in neuromuscular research: a 20-year analysis of race, ethnicity, sex, and age representation

Objectives: We conducted a systematic analysis of studies on neuromuscular diseases registered on ClinicalTrials.gov over the last 20 years to assess disparities in study populations. Methods: Data from interventional and observational neuromuscular disease studies initiated between January 1, 2004, and December 31, 2024, were retrieved from ClinicalTrials.gov and PubMed/MEDLINE. Collected variables included participant race, ethnicity, sex, eligible age range, mean and median ages, as well as study funding source, start year, and phase. These variables were analyzed to evaluate disparities in race, ethnicity, and age across studies and over time. Results: A total of 2166 studies were screened, with 462 meeting inclusion criteria, encompassing data from 37,131 participants. Most participants were male (61.4%), White (83.5%), and non-Hispanic/Latino (87.6%). While the proportion of studies reporting race and ethnicity increased over time (p < 0.001 and p = 0.001, respectively), the racial and ethnic composition of participants remained unchanged (p = 1). Studies on X-linked recessive disorders (i.e., Duchenne muscular dystrophy (DMD), Becker muscular dystrophy, and spinal and bulbar muscular atrophy (SMA)) predominantly excluded female participants. Regarding age accessibility, 37.9% of studies allowed children. Similarly, trial accessibility for older adults was limited. Even in studies with broader age eligibility, mean and median participant ages clustered around midlife, with underrepresentation at both age extremes. Notably, about half of DMD and SMA studies excluded participants over 16 and 18 years, respectively. Conclusion: Significant disparities persist in race, ethnicity, and age representation in neuromuscular disease clinical research, highlighting the need for more inclusive study designs.