The longevity glossary
Biology of aging
AMPK
AMPK (AMP-activated protein kinase) is an enzyme that acts as the cell's energy sensor, activating when ATP is low relative to AMP and triggering processes that restore energy balance, including autophagy.
Apoptosis
Apoptosis is a tightly regulated form of programmed cell death in which a cell activates its own controlled disassembly, allowing damaged or unneeded cells to be removed without triggering inflammation.
Autophagy
Autophagy (literally "self-eating") is the cellular process of enclosing damaged proteins and organelles in a membrane and breaking them down in the lysosome so their components can be reused.
Caloric Restriction
Caloric restriction is a sustained reduction in calorie intake below the amount needed for weight maintenance, without malnutrition, studied for its effects on metabolic health and lifespan.
Cellular Senescence
Cellular senescence is a stable state in which a cell stops dividing in response to damage or stress but does not die, instead persisting and secreting inflammatory signals that can harm nearby tissue.
Genomic Instability
Genomic instability is the progressive accumulation of DNA damage — mutations, chromosomal abnormalities, and impaired repair capacity — that occurs over a lifetime of exposure to replication errors, environmental mutagens, and internal stressors like reactive oxygen species.
Hallmarks of Aging
The hallmarks of aging are a framework of interconnected biological mechanisms — originally nine, expanded to twelve — proposed as the shared drivers underlying aging across tissues and species.
Hormesis
Hormesis is a biphasic dose-response phenomenon in which a low dose of a stressor triggers a beneficial adaptive response, while a high dose of the same stressor is harmful.
Inflammaging
Inflammaging is a state of chronic, low-grade, systemic inflammation that develops with advancing age, in the absence of overt infection, and is associated with most major age-related diseases.
Mitochondrial Dysfunction
Mitochondrial dysfunction refers to the age-related decline in mitochondrial number, efficiency, and quality control that reduces a cell's capacity to produce ATP and manage oxidative stress.
mTOR
mTOR (mechanistic target of rapamycin) is a protein kinase that senses nutrient and energy availability and, when active, drives cell growth and protein synthesis while suppressing autophagy.
NAD+
NAD+ (nicotinamide adenine dinucleotide) is a coenzyme present in every cell that is essential for energy metabolism and serves as a required cofactor for sirtuins and PARP enzymes involved in DNA repair.
Oxidative Stress
Oxidative stress is an imbalance between the production of reactive oxygen species (ROS) — chemically reactive molecules containing oxygen — and the body's antioxidant defenses, resulting in damage to lipids, proteins, and DNA.
Proteostasis
Proteostasis (protein homeostasis) is the network of cellular machinery — chaperones, the ubiquitin-proteasome system, and autophagy — that folds, refolds, and degrades proteins to keep the cell's protein pool functional.
Sirtuins
Sirtuins are a family of seven enzymes (SIRT1–SIRT7 in humans) that require NAD+ as a cofactor and regulate processes including DNA repair, gene expression, and mitochondrial function.
Stem Cell Exhaustion
Stem cell exhaustion is the age-related decline in the number and regenerative function of adult tissue stem cells, reducing the body's capacity to repair and replace damaged tissue.
Telomerase
Telomerase is an enzyme that adds telomere repeat sequences back onto the ends of chromosomes, counteracting the shortening that normally occurs with cell division.
Telomere
A telomere is a repetitive DNA sequence capping the end of each chromosome that protects it from degradation, and that shortens slightly with every cell division.
Biomarkers & testing
ApoB
ApoB (apolipoprotein B) is the main structural protein present on the surface of every LDL, VLDL, IDL, and lipoprotein(a) particle — the lipoproteins capable of depositing cholesterol into artery walls — with exactly one ApoB molecule per particle.
Biological Age
Biological age is an estimate of how much physiological wear a person's body shows relative to population norms, as opposed to chronological age, which is simply the number of years since birth.
DEXA Scan
DEXA (dual-energy X-ray absorptiometry) is an imaging scan that uses two low-dose X-ray beams at different energy levels to distinguish and quantify bone mineral density, fat mass, and lean (muscle) mass throughout the body.
Epigenetic Clock
An epigenetic clock is a mathematical model that estimates biological age from patterns of DNA methylation — chemical tags added to DNA that change predictably with age — at a defined set of genomic sites.
Frailty Index
A frailty index is a composite measure of age-related vulnerability calculated as the proportion of a large set of potential health deficits — symptoms, diseases, and functional impairments — that a given individual has, out of the total number tracked.
Gut Microbiome Testing
Gut microbiome testing analyzes DNA from a stool sample — typically via 16S rRNA sequencing or shotgun metagenomic sequencing — to characterize the bacterial species and their relative abundance living in the gut.
HbA1c
HbA1c (hemoglobin A1c) is a blood test that measures the percentage of hemoglobin that has become glycated (bound to glucose), reflecting average blood glucose levels over roughly the preceding two to three months, matching the lifespan of a red blood cell.
Heart Rate Variability
Heart rate variability (HRV) is the variation in time between consecutive heartbeats, used as a non-invasive indicator of autonomic nervous system activity and balance between its sympathetic and parasympathetic branches.
Homocysteine
Homocysteine is an amino acid produced as an intermediate in methionine metabolism; elevated blood levels (hyperhomocysteinemia) are associated with increased cardiovascular disease risk and, separately, cognitive decline.
hs-CRP
hs-CRP (high-sensitivity C-reactive protein) is a blood test that measures C-reactive protein at a much lower detection threshold than a standard CRP test, allowing it to detect the low-grade, chronic inflammation associated with cardiovascular risk rather than only acute infection.
VO2 Max
VO2 max is the maximum rate at which the body can take up and use oxygen during intense exercise, expressed in milliliters of oxygen per kilogram of body weight per minute, and is the standard measure of cardiorespiratory fitness.
Whole-Body MRI
Whole-body MRI is a magnetic resonance imaging scan of most or all of the body, marketed directly to healthy, asymptomatic adults as a general screening tool for cancer and other abnormalities, without the radiation exposure of CT scanning.
Therapies
Caloric Restriction Mimetics
Caloric restriction mimetics are compounds intended to reproduce some of the cellular signaling effects of caloric restriction — such as AMPK activation, mTOR inhibition, or autophagy induction — without requiring an actual sustained reduction in food intake.
Exosome Therapy
Exosome therapy is the administration of exosomes — small extracellular vesicles naturally released by cells that carry proteins, lipids, and RNA to communicate with other cells — typically derived from cultured stem cells, and marketed for tissue repair and anti-aging purposes.
Fasting-Mimicking Diet
A fasting-mimicking diet (FMD) is a structured, typically five-day, low-calorie and low-protein eating protocol designed to trigger metabolic changes similar to water-only fasting while still providing some nutrition.
GLP-1 Receptor Agonists
GLP-1 receptor agonists are a drug class that mimics the incretin hormone glucagon-like peptide-1, stimulating insulin release, suppressing glucagon, slowing gastric emptying, and reducing appetite — originally developed for type 2 diabetes and now widely used for weight management.
Hormone Replacement Therapy
Hormone replacement therapy (HRT) refers to prescription treatment with hormones — most commonly estrogen, often combined with progestogen — to replace levels that decline naturally with menopause or other endocrine changes.
Hyperbaric Oxygen Therapy
Hyperbaric oxygen therapy (HBOT) involves breathing near-100% oxygen inside a pressurized chamber, at pressures typically 1.5 to 3 times normal atmospheric pressure, to dramatically increase the amount of oxygen dissolved directly in blood plasma.
Intermittent Fasting
Intermittent fasting is an umbrella term for eating patterns that cycle between periods of voluntary food restriction (fasting windows) and periods of normal eating, rather than restricting the type or total daily amount of food consumed continuously.
IV Nutrient Therapy
IV nutrient therapy is the intravenous administration of vitamins, minerals, and other nutrients directly into the bloodstream, bypassing the digestive system's absorption limits, most commonly given as variations of the "Myers' cocktail" (a mix including B vitamins, vitamin C, and magnesium).
mTOR Inhibition
mTOR inhibition is a therapeutic strategy of pharmacologically reducing mTOR pathway signaling, most commonly with rapamycin or its analogs (rapalogs), based on the reproducible finding that this extends lifespan in multiple model organisms.
Peptide Therapy
Peptide therapy is the use of short chains of amino acids (shorter than a full protein) as therapeutic agents, designed to mimic or modulate the activity of naturally occurring signaling peptides in the body.
Photobiomodulation
Photobiomodulation (PBM), also called red light therapy or low-level laser therapy, is the application of specific wavelengths of red (approximately 630–700 nm) or near-infrared (approximately 700–1100 nm) light to skin or tissue at doses too low to produce a significant heating effect.
Senolytics
Senolytics are a class of compounds designed to selectively induce apoptosis (cell death) in senescent cells while sparing healthy cells, based on the premise that clearing this accumulated cell population could reduce the tissue damage caused by their inflammatory secretions.
Stem Cell Therapy
Stem cell therapy is the administration of stem cells — commonly derived from a patient's own bone marrow or fat tissue (autologous), or from donor umbilical cord or placental tissue (allogeneic) — with the goal of repairing or regenerating damaged tissue.
Testosterone Replacement Therapy
Testosterone replacement therapy (TRT) is prescription treatment with testosterone, indicated for men with clinically diagnosed hypogonadism — consistently low testosterone levels on repeated blood tests combined with associated symptoms.
Therapeutic Plasma Exchange
Therapeutic plasma exchange (TPE) is a medical procedure that removes a patient's blood plasma — the liquid component carrying antibodies, proteins, and other circulating factors — and replaces it with a substitute fluid (such as albumin solution or donor plasma), while returning the patient's own blood cells.
Compounds & drugs
Alpha-Ketoglutarate
Alpha-ketoglutarate (AKG) is a metabolic intermediate in the citric acid cycle (Krebs cycle) that also serves as a cofactor for enzymes involved in collagen synthesis and epigenetic regulation, and declines in circulating levels with age.
Berberine
Berberine is a bitter-tasting alkaloid compound found in several plants (including barberry and goldenseal), long used in traditional Chinese and Ayurvedic medicine, that activates AMPK and has been studied for effects on blood glucose and lipid metabolism.
Curcumin
Curcumin is the primary bioactive polyphenol in turmeric (Curcuma longa), studied for anti-inflammatory and antioxidant properties, whose clinical usefulness is heavily constrained by very poor natural oral bioavailability.
Dasatinib
Dasatinib is a tyrosine kinase inhibitor drug approved by the FDA for treating chronic myeloid leukemia and Philadelphia-chromosome-positive acute lymphoblastic leukemia, which was separately identified as having senolytic activity when combined with the flavonoid quercetin.
Fisetin
Fisetin is a flavonoid found in strawberries and several other fruits and vegetables that has been identified in laboratory screens as having senolytic activity — the ability to selectively induce death in senescent cells.
Melatonin
Melatonin is a hormone produced primarily by the pineal gland in response to darkness, which signals circadian timing to the rest of the body and is sold over the counter in many countries as a sleep aid.
NMN
NMN (nicotinamide mononucleotide) is a molecule that sits one enzymatic step upstream of NAD+ in its biosynthesis pathway, and is sold as an oral supplement intended to raise NAD+ levels.
NR
NR (nicotinamide riboside) is a form of vitamin B3 and a precursor in the NAD+ salvage pathway, absorbed via well-characterized nucleoside transporters and converted to NAD+ through fewer, better-established enzymatic steps than NMN.
PQQ
PQQ (pyrroloquinoline quinone) is a small redox-active compound found in trace amounts in various foods (including fermented soybeans, parsley, and green tea) that has been studied in animal and cell models for a role in stimulating mitochondrial biogenesis.
Quercetin
Quercetin is a flavonoid found widely in fruits and vegetables (including onions, apples, and berries) that, in combination with the chemotherapy drug dasatinib, forms the most-studied senolytic drug combination, known as "D+Q."
Resveratrol
Resveratrol is a polyphenol compound produced by certain plants (notably grape skins, and therefore red wine) in response to stress or fungal infection, popularized as a longevity compound after early research suggested it activated sirtuins.
Urolithin A
Urolithin A is a compound produced by gut bacteria metabolizing ellagitannins — polyphenols found in pomegranates, walnuts, and some berries — that has been shown in preclinical models to activate mitophagy, the selective autophagic clearance of damaged mitochondria.
General & clinical
Blue Zones
Blue Zones are a set of geographic regions — originally Sardinia (Italy), Okinawa (Japan), Nicoya (Costa Rica), Ikaria (Greece), and Loma Linda (California) — identified by demographic researchers as having unusually high concentrations of people reaching age 100, studied for common lifestyle patterns that might explain this.
Compounding Pharmacy
A compounding pharmacy prepares customized medications for an individual patient — combining, mixing, or altering drug ingredients — to meet a specific prescription need that a commercially manufactured, FDA-approved product does not meet, such as a different dose, a removed allergen, or an alternate delivery form.
Confounding Variable
A confounding variable is a factor that is associated with both the exposure or treatment being studied and the outcome being measured, and that can create or distort an apparent association between the two even when no true causal relationship exists between them.
Evidence Grade
Evidence grade is this site's letter rating (A through D) of how strongly human clinical data supports a given compound or therapy, assigned strictly on the basis of human study results rather than animal or cell-culture data.
Healthspan vs. Lifespan
Lifespan is the total number of years a person lives; healthspan is the portion of that lifespan spent free of significant chronic disease, disability, or functional decline.
Longevity Escape Velocity
Longevity escape velocity is a hypothesis — not an established scientific finding — proposing that if biomedical advances extend healthy life expectancy faster than one year per calendar year, a person alive when this threshold is reached could theoretically avoid dying of age-related causes indefinitely, as each year buys more than a year of additional life expectancy.
Observational Study
An observational study is a research design in which researchers measure and analyze outcomes as they naturally occur, without assigning participants to a particular exposure or treatment the way a randomized controlled trial does.
Off-Label Prescribing
Off-label prescribing is the practice of a licensed prescriber prescribing an approved drug for an indication, patient population, dose, or route of administration that has not been specifically evaluated and approved by the relevant regulatory agency for that use.
Randomized Controlled Trial
A randomized controlled trial (RCT) is a study design in which participants are randomly assigned to receive either the intervention being tested or a comparison (control) condition, allowing researchers to isolate the treatment's effect from other influences.
Sarcopenia
Sarcopenia is the progressive, age-related loss of skeletal muscle mass, strength, and physical function, distinct from simple muscle loss from disuse in that it is driven by a combination of biological aging processes.
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