Diagnostic and inclusion criteria in Alzheimer's disease clinical trials: A systematic review of the past decade.

Background: Dementia, mainly caused by Alzheimer's disease (AD), is a leading cause of mortality and disability in the elderly. However, inconsistencies in diagnostic and inclusion criteria challenge the design and comparability of AD clinical trials. Objective: To review recent AD clinical trials, focusing on diagnostic methods and inclusion criteria, and identify trends and gaps to inform future research. Methods: We systematically searched Web of Science, PubMed, and Google Scholar for AD clinical trials, extracting data on diagnostic criteria, disease stage, cognitive assessments, biomarker use, and participant age. Results: Of the 27,471 articles screened, 71 studies were included in the final review. Most were conducted in North America (52%) and Europe (34%). NINCDS-ADRDA (56%) and NIA-AA 2011 (30%) were the most used diagnostic criterion, with the latter increasingly adopted in recent years. Over half focused on mild-to-moderate AD (56%), 16% on mild AD, and 13% included mild cognitive impairment/mild AD populations, with growing interest in early-stage interventions. However, only a minority reported notable cognitive improvements. The Mini-Mental State Examination was the most frequently used assessment tool (86%), though 36 different cutoff schemes were identified. Biomarkers were used in 38% of studies, mainly in the past three years, while others relied on symptom-based or imaging approaches. Participants ranged from 45 to 95 years old, with 50 as the most common lower age limit. Conclusions: Symptom-based criteria still dominate AD trials. Given the limited efficacy of single interventions, future studies should consider multimodal, non-invasive approaches and prioritize objective biomarkers to enhance consistency and diagnostic precision.