Racial and ethnic diversity in clinical studies reported to ClinicalTrials.gov, 2009–2024

Abstract

Objective: A lack of transparent reporting of race and ethnicity in clinical research limits the ability to identify health inequities and evaluate to what extent clinical research includes diverse populations. Our objectives are: (1) to identify study characteristics associated with reporting race and ethnicity of clinical study participants and (2) to document temporal trends in race and ethnicity reporting on ClinicalTrials.gov. Design: Cross-sectional analysis of interventional trials and observational studies from 2009 to 2024; multivariable logistic regression assessed study-level factors associated with reporting race and ethnicity. Setting: Global registry of clinical studies (ClinicalTrials.gov). Participants: 58 163 studies with posted results and without early termination. Exposures: Study characteristics: sponsor trial phase, study type and country. Main outcomes and measures: Reporting of race, reporting of ethnicity, reporting of both. Results: Among 58163 studies (mean enrolment=1215 participants), 44.8% did not report race or ethnicity to the repository (mean enrolment=1481 participants). The proportion of studies reporting both race and ethnicity rose from 7.4% in 2013 to 54.6% in 2024. In multivariable models, observational studies had lower odds of reporting race and ethnicity (OR 0.55, 95% CI 0.49 to 0.61) compared with interventional trials. Phase 4 trials were least likely phase to report race and ethnicity (OR=0.32; 95% CI 0.29 to 0.35), and studies with only National Institute of Health funding were more likely to report race and ethnicity compared with studies with any industry funding or sponsorship (OR=1.70, 95% CI 1.61 to 1.79). For studies that reported race, White participants comprised ≥50% each year based on study-level percentages; proportions of Asian participants declined, and Black participants fluctuated. ‘Not Hispanic or Latino’ remained ≥80% of reported ethnicity annually. Conclusions: Race and ethnicity reporting on ClinicalTrials.gov has improved markedly yet remains incomplete, with shortfalls in late-phase and observational studies.