INTRODUCTION

Alzheimer's disease and related dementias (ADRD) affect an estimated 55–57 million people worldwide, a burden projected to nearly triple by 2050. Growth is fastest in low- and middle-income countries (LMICs), where 60% of people with dementia already live, rising to 71% by 2050. This review synthesizes 2020–2026 literature on ADRD trial characteristics, geography, participant diversity, and outcomes, mapping disparities across continents and income strata.

METHOD

We synthesized registry-based landscape analyses (ClinicalTrials.gov, WHO ICTRP), annual drug-development pipeline reports, bibliometric analyses, and systematic/scoping reviews addressing ADRD trial geography, diversity, and outcomes, identified via structured searches of publicly indexed literature (2020–2026). Findings were synthesized narratively across six themes: trial volume, phase/design, therapeutic targets, geographic distribution, participant diversity, and clinical outcomes.

RESULTS

Only 11.6% of 1,237 disease-modifying therapy trials were conducted in emerging economies. Pooled analysis of 12 pivotal anti-amyloid trials (16,055 participants) found enrollment 85.1% White, 7.8% Asian, 1.2% Black, spanning 164 countries of which only 15.2% were LMICs. Among 88 US Phase III trials (1997–2023), two decades of compound failures (2004–2021) show 51% failing in Phase III and 49% in Phase II, while lecanemab and donanemab mark the first disease-modifying approvals in nearly 20 year

CONCLUSION

ADRD trials remain concentrated in North America, Western Europe, and high-income Asia-Pacific settings, with systematic under-representation of Africa, Latin America, South Asia, and the Middle East. Even in high-volume settings, racial and ethnic minorities remain under-represented and inconsistently reported.