Assessing the relationships between frailty, sarcopenia and Alzheimer's disease biomarkers: a scoping review.

INTRODUCTION

While both frailty and sarcopenia have been linked with the Alzheimer’s disease (AD) clinical phenotype, their association with AD pathophysiology is unclear. This review aimed to identify current evidence of relationships between frailty, sarcopenia and AD biomarkers.

METHODS

Four databases (Ovid MEDLINE, Embase, PsycINFO, Web of Science) were searched for articles that explored relationships between frailty or sarcopenia and AD biomarkers.

AD biomarkers (fluid, tissue, neuroimaging) were defined by the 2024 criteria for diagnosis and staging of AD: Alzheimer’s Association Workgroup. Assessment of frailty and sarcopenia were by use of a method/tool defined by the authors of the study.

RESULTS

8187 articles were screened, with 49 studies included (31 frailty, 22 sarcopenia, 4 both).

For frailty, the main AD biomarkers evaluated were hippocampal volume (35%) and beta-amyloid [Aβ] positron electron tomography (PET) (29%). For sarcopenia, the most common AD biomarkers evaluated were hippocampal volume (36%) and Aβ PET (55%).

The findings were limited by the heterogeneity of the available evidence, in particular, the variability in frailty/sarcopenia definitions, AD biomarker assessments and the predominance of cross-sectional studies. Potential associations were identified across some studies, but these associations were not consistent across all studies.

CONCLUSIONS

Conclusions are limited by substantial heterogeneity in the assessment of frailty, sarcopenia, AD biomarkers, and a lack of longitudinal data.

Future studies are needed that include longitudinal analyses, consensus in AD biomarker, frailty and sarcopenia assessments, and incorporation of novel AD biomarkers, in particular tau and neuroinflammation, to help clarify these relationships.