Abstract
Background and Objectives: The aim of this study is to categorize and combine (according to the source of biomaterial) biomarkers of frailty syndrome and identify challenges in research on these biomarkers by reviewing the current literature from the past five years. Methods: We systematically searching five electronic databases—PubMed, Scopus, Web of Science, CINAHL, and the Cochrane Library—for citations from 1 January 2019 to 1 July 2024. We conducted a qualitative data synthesis and categorized the limitations by topics and subtopics. PROSPERO—CRD: 42024491369. Results: A total of 61 papers met the criteria for inclusion in this study. These studies included a total of 56,758 participants, and 1479 unique biomarkers. We categorized biomarkers such as blood, genetic, urinary, and salivary biomarkers. Our analysis identified three major categories of challenges: challenges related to study design, unclear pathophysiological mechanisms, and biomarker-specific challenges. Conclusions: This review underscores the extensive research into biomarkers associated with frailty syndrome, such as blood, genetic, urinary, and salivary biomarkers. However, significant challenges persist, including methodological inconsistencies, biomarker measurement variability, and a limited understanding of underlying mechanisms.