Journal of Disease and Global Health

Global disparities in dementia diagnosis remain substantial, driven by unequal access to diagnostic tools, limited research infrastructure in low- and middle-income countries, and the persistent underrepresentation of non-European populations in dementia research. Drawing on evidence from major longitudinal cohorts, systematic reviews, population-based studies, and international research initiatives, this review examines how advances in cerebrospinal fluid, imaging, plasma, and digital biomarkers have reshaped early dementia detection. However, the validation of these biomarkers has relied predominantly on cohorts from high-income settings, limiting their generalizability and clinical accuracy in diverse populations. We synthesize evidence demonstrating that interacting genetic, metabolic, vascular, environmental, and sociocultural factors influence dementia risk at multiple biological levels from cellular and molecular pathways to systemic and cognitive phenotypes resulting in population-specific biomarker expression. These differences have direct clinical implications, including misclassification, delayed diagnosis, and inequitable access to biomarker-dependent therapies. The review highlights critical representation gaps in existing biomarker cohorts and discusses methodological challenges in global validation. Finally, we propose a framework for developing multi-ethnic, globally representative dementia biomarker cohorts through ethical governance, infrastructure investment in low- and middle-income countries, and the adoption of scalable plasma and digital biomarkers. Advancing biomarker equity is essential for improving diagnostic validity and building a globally inclusive dementia research and care ecosystem.