Long-Term Trends in Racial and Ethnic Reporting and Representation in US Alzheimer's Clinical Trials

Alzheimer's disease (AD) disproportionately burdens racial and ethnic minority populations, yet the extent to which US clinical trials reflect this burden remains poorly understood. We conduct a systematic review of all 88 completed US-based Phase III AD drug trials between 1997 and 2023, using a multi-source approach that integrates the Trialtrove clinical trial database with PubMed, ClinicalTrials.gov, pharmaceutical reports, and conference abstracts. We document three main findings. First, nearly half of published trials (49.3%) reported no data on patient race or ethnicity. Among trials that did report, practices were highly inconsistent in terminology, categorization, and analytical depth. Second, White patients constituted a median of 91.3% of enrollment, while Black patients represented 4.5%-7.2%, Hispanic patients 5.2%, and Asian / Pacific Islander and Native American patients less than 1% - shares that are grossly disproportionate to AD prevalence rates, which are approximately twice as high among non- Hispanic Black older adults and 1.5 times as high among Hispanic older adults relative to non- Hispanic Whites. Third, only 3 trials (4.2%) conducted any subgroup analyses by race or ethnicity, and none reported treatment safety or efficacy stratified by demographic group. Critically, regression models find no evidence of improvement in reporting or representation from 1997 to 2023. These patterns limit the generalizability of existing AD treatment evidence and raise fundamental concerns about health equity. Our findings support strengthening mandatory reporting standards, broadening eligibility criteria, and diversifying trial site selection to ensure emerging AD treatments are evaluated equitably across the populations most affected.