Racial and Ethnic Reporting and Representation in US Alzheimer Clinical Trials: A Systematic Review.

IMPORTANCE: Alzheimer disease (AD) disproportionately affects racial and ethnic populations underrepresented in US clinical research, raising concerns about the generalizability of AD trial findings and the evaluation of treatment safety and efficacy for populations most affected by AD. OBJECTIVE: To examine patterns and trends in the reporting and representation of patient race and ethnicity in US-based phase 3 AD clinical trials. EVIDENCE REVIEW: This systematic review examined US-based phase 3 AD drug trials identified through the Trialtrove trial database between 1997 and 2023. Trials were cross-referenced with peer-reviewed publications, ClinicalTrials.gov, pharmaceutical company reports, and conference abstracts. Completed trials were eligible for inclusion if they were designated as phase 3 drug trials targeting AD and recruited patients exclusively in the US. Primary outcomes included reporting of race and ethnicity, the number of racial and ethnic groups reported, and their representation among trial populations. Secondary outcomes included terminology used, reporting of safety or efficacy differences by race and ethnicity, and discussion of racial and ethnic representation in trial reports. Temporal trends in reporting and representation were assessed. Methodologic quality was evaluated using the Quality Rating Scheme for Studies and Other Evidence. Data collection was completed May 2024. FINDINGS: Among 88 US-based phase 3 AD clinical trials conducted between 1997 and 2023, 71 (80.7%) had publicly available results, including 52 (59.1%) published in peer-reviewed journals. Nearly half of published trials (35 [49.3%]) did not report patient race or ethnicity. Among published trials, reporting was inconsistent and focused predominantly on White (36 [50.7%]) patients, with substantially fewer trials reporting data on Asian or Pacific Islander (11 [15.5%]), Black (20 [28.2%]), Hispanic (13 [18.3%]), or Native American (2 [2.8%]) patients. Median (IQR) enrollment of White patients was 91.3% (87.3%-93.6%), whereas enrollment of underrepresented patient populations was markedly lower, with median (IQR) enrollment of 0.9% (0.6%-1.6%) for Asian or Pacific Islander, 4.5% (3.6%-6.6%) for Black (ethnicity unspecified), 7.2% (3.7%-9.1%) for Black (non-Hispanic), 5.2% (3.1%-6.6%) for Hispanic, and 0.4% (0%-0.8%) for Native American patients. Few trials (3 of 71 [4.2%]) conducted subgroup analyses by race or ethnicity, and none reported detailed subgroup characteristics or safety or efficacy outcomes by patient race and ethnicity. Reporting practices and representation showed little improvement over time. CONCLUSIONS AND RELEVANCE: US-based phase 3 AD trials showed substantial gaps in racial and ethnic reporting and representation from 1997 to 2023, limiting the evaluation of treatment safety and efficacy across diverse populations. These findings suggest that stronger reporting standards and more inclusive trial design and recruitment strategies are needed to improve the equity and generalizability of AD trials.