The 12 Hallmarks of Aging: A Complete Guide

For most of medical history, aging was treated as a single, undifferentiated process — something that just happened to the body, like rust on a car. That view collapsed in 2013, when a landmark paper by Carlos López-Otín and colleagues proposed the "hallmarks of aging" framework: a short list of cellular and molecular processes that together drive the phenotype we call aging. The original paper listed nine hallmarks. In 2023 the same group added three more, bringing the total to twelve.

The hallmarks framework matters because it gives researchers — and you — a map. Instead of treating each age-related disease (Alzheimer's, heart disease, osteoarthritis, type 2 diabetes) as a separate problem, we can ask which hallmarks underlie all of them, and target the hallmarks directly. This guide walks through all twelve hallmarks in plain English, explains the evidence, and tells you what actually moves the needle on each one.

If you're new to longevity science, start with our biological age primer and the beginner longevity protocol — then come back here for the deeper biology.

What are the hallmarks of aging?

A "hallmark" in this context has three properties: (1) it manifests during normal aging; (2) accelerating it experimentally accelerates aging; and (3) slowing or reversing it experimentally extends healthspan. The original nine were organized into three categories — primary hallmarks (causes of damage), antagonistic hallmarks (responses to damage), and integrative hallmarks (systemic consequences). The three added in 2023 round out the framework and reflect a decade of new research.

The framework is not the final word. Some researchers argue it under-emphasizes mechanical and structural aging (stiffening arteries, glycation of collagen), while others point out that the hallmarks are interconnected and don't cleanly separate. But it remains the most useful organizing tool the field has — and it's the lens through which most geroscience is now conducted.

The original nine hallmarks (2013)

The 2013 paper proposed nine hallmarks: genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and altered intercellular communication. For nearly a decade this was the canonical list taught in graduate courses and cited in thousands of papers.

The three new hallmarks (2023)

In a 2023 update, López-Otín and colleagues added three hallmarks: chronic inflammation (inflammaging, previously folded into "altered intercellular communication"), dysbiosis (age-related changes in the gut and other microbial communities), and disabled macroautophagy (the gradual failure of the cell's recycling system). Each had been hinted at in earlier literature but had grown enough evidence to stand on its own.

1. Genomic instability

Every cell in your body suffers tens of thousands of DNA lesions per day from UV light, reactive oxygen species, replication errors, and environmental mutagens. Most are repaired by an army of DNA repair enzymes, but a small fraction slips through. Over decades, mutations accumulate — particularly in long-lived cells like neurons and muscle fibers. The result: rising risk of cancer, declining tissue function, and cellular senescence.

What helps: avoiding cigarette smoke and excessive sun; limiting alcohol; eating a polyphenol-rich diet (berries, olive oil, tea, coffee); and getting adequate folate, B12, and niacin (which fuel DNA repair enzymes). NAD+ precursors like NMN support PARP enzymes, the major DNA repair family.

2. Telomere attrition

Telomeres are the protective caps at the ends of chromosomes. Each time a cell divides, telomeres shorten by ~50–100 base pairs. When they get too short, the cell enters senescence or dies. Telomere attrition is most relevant in tissues with rapid cell turnover (immune cells, gut lining, skin). Elizabeth Blackburn won the 2009 Nobel Prize for discovering telomerase, the enzyme that lengthens telomeres — but telomere length turns out to be only one piece of the aging puzzle. See our telomeres guide for the deeper dive.

3. Epigenetic alterations

The epigenome is the set of chemical modifications (DNA methylation, histone acetylation) that controls which genes are turned on and off in each cell. With age, the epigenetic patterns drift — genes that should be silent get expressed, genes that should be active get silenced. This drift is so consistent that epigenetic clocks like Horvath's can estimate biological age from a sample of DNA with high accuracy.

Excitingly, this hallmark looks reversible. In 2023, Sinclair's lab restored vision in old mice by transiently expressing three Yamanaka factors to "reprogram" retinal cells to a younger epigenetic state. Yamanaka reprogramming in live animals is still risky — too much expression causes tumors — but partial reprogramming is one of the most promising frontiers in longevity science.

4. Loss of proteostasis

Proteostasis = protein homeostasis. Cells must fold, maintain, and degrade billions of protein molecules. With age, the systems that handle this (chaperones, the ubiquitin-proteasome system, autophagy) become less efficient. Misfolded proteins aggregate, forming the amyloid plaques of Alzheimer's, the Lewy bodies of Parkinson's, and the lipofuscin granules that age every tissue. Heat shock, exercise (which upregulates chaperones), and fasting all boost proteostasis.

5. Deregulated nutrient sensing

Cells have evolved to sense whether food is plentiful or scarce and adjust metabolism accordingly. The key pathways: insulin/IGF-1 (signals "fed"), mTOR (signals "growth"), AMPK (signals "low energy"), and sirtuins (signal "low energy, activate repair"). When food is constant and abundant — modern life — these pathways stay in growth mode and never switch to repair mode. The result: accelerated aging. Caloric restriction, fasting, and exercise flip the switches back. See our deep dive on mTOR vs AMPK.

6. Mitochondrial dysfunction

Mitochondria are the power plants of the cell, generating ATP via oxidative phosphorylation. With age, mitochondria accumulate damage, become less efficient, and produce more reactive oxygen species. NAD+ levels drop, sirtuin activity falls, and mitophagy (the recycling of old mitochondria) slows. The result: declining energy production, rising oxidative stress, and tissue dysfunction. This is the hallmark where NAD+ boosters, CoQ10, PQQ, and exercise have the clearest impact. See our mitochondrial health guide.

7. Cellular senescence

When cells accumulate too much damage, they often enter a state called senescence — they stop dividing but don't die. Senescent cells secrete a toxic cocktail of inflammatory cytokines (the SASP, senescence-associated secretory phenotype) that damages neighboring cells and drives chronic inflammation. The number of senescent cells rises with age, and clearing them with senolytic drugs (dasatinib + quercetin, fisetin, navitoclax) extends healthspan in mice. Fisetin, found in strawberries, is one of the most promising natural senolytics. See our inflammaging guide for how senescent cells drive system-wide inflammation.

8. Stem cell exhaustion

Most tissues have small reservoirs of stem cells that replenish damaged or aging cells. With age, these reservoirs shrink — both because stem cells divide less and because they accumulate damage. The result: tissues regenerate more slowly, wounds heal more slowly, immune function declines. Exercise, caloric restriction, and certain supplements (spermidine, metformin) help preserve stem cell function. Stem cell therapies are being explored clinically but are not yet standard longevity interventions.

9. Altered intercellular communication

Cells don't age in isolation — they signal to each other via hormones, cytokines, and exosomes. With age, this signaling becomes more inflammatory and less coordinated. Old cells secrete pro-inflammatory signals (the SASP) that "age" their neighbors; young cells can "rejuvenate" old ones in heterochronic parabiosis experiments (where blood is shared between old and young mice). This hallmark is partly why inflammaging matters systemically.

10. Chronic inflammation (inflammaging)

Inflammaging — chronic, low-grade, sterile inflammation that rises with age — was promoted to a full hallmark in 2023. It's driven by senescent cells, gut dysbiosis, visceral fat, chronic infections (CMV), and molecular debris. Inflammaging underlies cardiovascular disease, neurodegeneration, cancer, frailty, and immune decline. Measurable as elevated CRP, IL-6, and TNF-α. Lowered by exercise, sleep, omega-3, curcumin, and weight loss. See our full inflammaging guide.

11. Dysbiosis

The trillions of bacteria, fungi, and viruses that live in your gut (and on your skin, in your mouth, in your airways) change with age. Beneficial bacteria that produce short-chain fatty acids like butyrate decline, while pro-inflammatory species rise. This dysbiosis contributes to inflammaging, leaky gut, immune dysfunction, and possibly neurodegeneration (via the gut-brain axis). Diet (fiber, polyphenols, fermented foods), probiotics, and prebiotics help. See our gut health and aging guide and our microbiome test guide.

12. Disabled macroautophagy

Autophagy (literally "self-eating") is the cell's recycling system: damaged proteins and organelles are engulfed in vesicles and broken down for raw materials. With age, autophagy slows — and the resulting buildup of cellular garbage drives neurodegeneration, inflammation, and metabolic dysfunction. The good news: autophagy is one of the most reliably activatable hallmarks. Fasting (16+ hours), exercise, spermidine, resveratrol, and rapamycin all boost it. Spermidine is one of the most consistent autophagy activators in animal models.

What actually works against the hallmarks?

No single intervention hits all twelve hallmarks. But a small set of high-leverage behaviors and compounds cover most of them:

• Exercise (Zone 2 + strength) — improves mitochondrial function, proteostasis, stem cell function, insulin sensitivity, inflammation. The single highest-leverage intervention. See our exercise guide.
• Sleep (7–9 hours, optimized) — supports DNA repair, proteostasis, immune function, and lowers inflammation. See our sleep guide.
• Caloric restriction or time-restricted eating — activates AMPK, sirtuins, autophagy; lowers mTOR. See our fasting guide.
• Whole-food, plant-forward diet — supports gut microbiome, lowers inflammation, provides polyphenols. See our diet guide.
• NAD+ boosters (NMN, NR) — fuel sirtuins and PARP, supporting DNA repair, mitochondrial function, and epigenetic maintenance.
• Spermidine — activates autophagy, one of the most reliable ways to slow proteostasis decline.
• Fisetin and other senolytics — clear senescent cells, lowering inflammaging.
• Rapamycin (prescription) — inhibits mTOR, extends lifespan in mice. See our rapamycin guide.

For the mitochondrial hallmark specifically, we like Renue's liposomal NMN as a high-bioavailability NAD+ booster:

For the autophagy hallmark, spermidine is the most consistent over-the-counter activator:

And for the senescence hallmark, fisetin is the most-studied natural senolytic:

The bottom line

The hallmarks framework is the best map we have of aging. It explains why a single disease-focused approach to medicine is insufficient — because all age-related diseases share underlying hallmarks. It also explains why a small set of behaviors (exercise, sleep, fasting, whole foods) protects against so many conditions at once: they hit multiple hallmarks simultaneously.

The frontiers are still being mapped. Epigenetic reprogramming (Yamanaka factors), senolytic drugs, NAD+ boosters, and rapamycin are the most exciting. But you don't need to wait for the next breakthrough to start: most of what works against the hallmarks is already available today, mostly for free. For the full lifestyle playbook, see our guide to lowering biological age and our supplement stack guide.