Relationship between frailty and Alzheimer's disease biomarkers: A scoping review

INTRODUCTION: Frailty and dementia appear to be closely linked, although mechanisms remain unclear. The objective was to conduct a scoping review of the association between frailty and Alzheimer's disease (AD) biomarkers in humans. METHODS: Three databases, PubMed, PsycINFO, and Embase, were searched for articles using the following search terms: “frail elderly”, “Alzheimer's disease”, “dementia biomarkers” and their synonyms. Inclusion was limited to original research in humans published before 2017, which included a frailty measure and AD biomarker (fluid markers, neuroimaging, and neuropathology). RESULTS: Five hundred twenty-two articles were identified and screened; 10 were included. Most were cross-sectional (n = 6), measured the frailty phenotype (n = 6), and included people with dementia (n = 7). Biomarkers examined were postmortem AD pathology (n = 3), brain atrophy (n = 5), and in vivo fluid markers (n = 2). Eight studies reported that increased frailty was associated with at least one biomarker abnormality. DISCUSSION: Evidence is limited and suffers from design limitations but suggests that frailty and AD biomarkers are closely linked. Longitudinal research examining multiple biomarkers and frailty is warranted.