Biomarkers of Frailty

Several biomarkers have been proposed to identify the multisystemic age-related syndrome, frailty. However, due to its complex pathophysiology and the lack of consensus for a comprehensive definition of this syndrome, the existence of a unique biomarker or set of biomarkers is still lacking and challenging. In this review, we address the main laboratory biomarkers, with special emphasis on those related to different pathways tightly linked to the frailty condition such as inflammation, oxidative stress, and metabolic alterations. In addition, we summarize different imaging biomarkers related to frailty (Dual Energy X-ray Absorptiometry, Bioelectrical Impedance analysis, Computed Tomography and Magnetic Resonance Imaging, and Ultrasound). Despite the number of available biomarkers, the evidence is still limited, since many of them have been associated with frailty only cross-sectionally, and very few studies have assessed the longitudinal influence of these biomarkers on different trajectories or transitions of frailty. Considering the multicausality of frailty, there is an increasing need to assess the role of sets of biomarkers and combining laboratory, clinical, and imaging biomarkers to determine their value in improving the sensitivity, specificity, and predictive values to diagnose frailty as compared with the usual clinical criteria.