Aging and Biomarkers: An Overview

Definition of Aging: Aging is a multifaceted decline in function over time that affects most living organisms. It encompasses processes that diminish an individual's health and survival. While chronological age is a measure of time, "biological age" can differ significantly from it.

Biomarkers: A biomarker is a measurable feature that indicates a biological state or condition. Biomarkers of aging are believed to be more accurate predictors of future health and longevity than chronological age. They should be consistent, cause minimal trauma to the individual, and be reproducible. Currently, there isn't a universally accepted single-measurement biomarker of aging due to the complexity of the aging process. Many believe that a combination of biomarkers will be necessary to confidently predict aging outcomes. Recent studies have shown that composite biomarkers might be more effective than individual ones.

Types of Biomarkers:

• Laboratory Measurements: Examples include telomere length and epigenetic clocks.
• Routine Laboratory Biomarkers: These are standard measurements like complete blood count, inflammation markers, and markers indicating organ function.
• Molecular Biomarkers: These are primarily genome-level biomarkers.
• Non-molecular Phenotypic Biomarkers: These describe physiological functions, such as physical capability and organ function.
• Diagnostic Biomarkers: Used to diagnose or confirm diseases.
• Prognostic Biomarkers: Predict the progression of a disease or dysfunction.
• Predictive Biomarkers: Monitor the success or failure of treatments.

Relevance and Effort Scores: The study investigated the citation profiles of potential aging biomarkers to determine their "relevance," which serves as an indicator of their predictive accuracy. Each biomarker was also assigned an "effort score" (e-score) to estimate the effort required for its measurement.

Research on Aging Biomarkers: Numerous researchers have endeavored to identify potential aging biomarkers. Most reviews in this field focus on specific subsets of markers. The goal of the provided review is to summarize frequently mentioned potential aging biomarkers and suggest effort scores. It acknowledges the subjectivity in determining effort scores and citation profiling scores. The review aims to assist in selecting aging-related biomarkers based on relevance and effort, rather than proposing a comprehensive aging marker.