Longevity and Aging Research Glossary

This glossary explains words you will meet in longevity and aging research. It is education only. A definition tells you what a term means in research, not whether a product or medicine works, and none of it is advice to start, stop or change any treatment. Evidence labels such as preclinical and promising but limited are explained on How We Label Evidence in Longevity Research.

Aging and age

• Ageing (aging): at the biological level, the result of molecular and cellular damage building up over time, leading to a gradual decrease in physical and mental capacity and a growing risk of disease. [1] See What Is Aging?.
• Chronological age: age in years. Health changes are only loosely associated with age in years. [1]
• Biological age: an estimate of aging based on body measurements rather than the calendar. Researchers have studied epigenetic clocks, telomere length and other predictors, and a 2017 review said the true value of the epigenetic clock needs longitudinal confirmation. [2] See Biological Age vs Chronological Age.
• Lifespan, healthspan, maximum lifespan: how long a life lasts, how many of those years are healthy, and the longest recorded life in a species. See Lifespan vs Healthspan vs Maximum Lifespan.
• Geroscience: a field that aims to define and modify aging-related biologic pathways, slow age-related disability, prevent age-related diseases and increase disability-free survival. [3]
• Hallmarks of aging: a framework of twelve features proposed in 2023, among them genomic instability, telomere attrition, cellular senescence and chronic inflammation. [4] It is a research framework, not a treatment map. See The Hallmarks of Aging.
• Frailty: a state of vulnerability to poor recovery after a stressor event, resulting from cumulative decline in many body systems. [5]
• Sarcopenia: described in a European consensus as a muscle disease (muscle failure) rooted in adverse muscle changes across a lifetime, with low muscle strength as a key feature. [6]
• Inflammaging: chronic, sterile, low-grade inflammation that develops during aging and is thought to contribute to age-related disease. [7] See Inflammaging.

Cell and molecular terms

• Cellular senescence: a cell state implicated in physiological processes and a wide range of age-related diseases. [8]
• Senescence-associated secretory phenotype (SASP): factors released by senescent cells that can cause inflammation and dysfunction. [9]
• Senolytic: a drug intended to remove senescent cells. In an open-label phase 1 pilot of dasatinib plus quercetin in nine people with diabetic kidney disease, cell markers fell, and the authors disclosed patents held by Mayo Clinic. [9] See Cellular Senescence Explained.
• Autophagy: a self-degradative process that balances energy sources and removes misfolded proteins and damaged organelles. [10] See Autophagy Explained.
• mTOR: a signaling pathway. Rapamycin, an inhibitor of the mTOR pathway, extended lifespan in genetically varied mice. [11] That is a mouse result, not a human one. See mTOR, AMPK and Nutrient-Sensing Pathways.
• NAD+ and sirtuins: NAD is a coenzyme in metabolic pathways and a substrate for sirtuin enzymes. [12] A review said the clinical evidence that raising NAD+ improves physiological function is unclear. [13]
• Telomere: the protective end of a linear chromosome. [14] See Telomeres and Aging.
• DNA methylation and epigenetic clock: DNA methylation levels can be used to build predictors of age; one multi-tissue predictor used 353 sites. [15] Such clocks need validation before clinical use. [16]
• DunedinPACE: a blood DNA methylation measure of the pace of aging, associated with illness, disability and death in its development study. [17] See Biological Age Clocks Compared.

Measures and endpoints

• Biomarker: a measurable signal in the body. A biomarker of aging is not a health outcome, and no consensus exists on how such biomarkers should be validated before clinical use. [16]
• Surrogate endpoint: a trial endpoint used as a substitute for a direct measure of how a patient feels, functions or survives. [18] See Surrogate Endpoints and Aging Biomarkers in Trials.
• Clinical outcome: a direct measure of how a person feels, functions or survives. [18]
• Disability-free survival: a combined endpoint used in the ASPREE trial: death, dementia or persistent physical disability. [19]

Study design terms

• Preclinical: work in cells or animals. The National Institute on Aging Interventions Testing Program identifies agents that extend lifespan and healthspan in mice. [20]
• Observational study: a study that does not test a medical intervention but watches people over time. [21]
• Clinical trial: a study that tests a medical, surgical or behavioral intervention in people. [21] See Reading Longevity Studies.
• Randomized trial: participants are randomly assigned to groups, such as aspirin or placebo. [19]
• Pilot study: a small early study, such as a nine-person phase 1 trial. [9]
• Systematic review and meta-analysis: a review that follows a stated method, and a statistical pooling of results. PRISMA is a reporting guideline for systematic reviews. [22] A 2023 physical activity paper is an example of a systematic review with a dose-response meta-analysis. [23]
• Trial registration: listing a trial publicly before it enrolls people; the ICMJE says failing to do so risks inadmissibility to its journals. [24] See How to Find Longevity Studies and Trial Records.
• Preprint and retraction: PubMed notes that preprints are among the citations not indexed for MEDLINE, and it has a Retracted Publication type. [25]
• Conflict of interest: a financial or other stake in the result. One rapamycin trial disclosed that several authors were employees and shareholders of a company offering the medicine. [26]