The hallmarks of aging, and the three tests that decide the list

What the framework actually claims

In 2013 a group of researchers proposed that the bewildering biology of aging could be organized into 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.^[1] The paper has since been cited more than twenty thousand times, which tells you how badly the field wanted an organizing structure.

What is often lost is that the framework is a proposal about how to think, not an inventory of facts. It was built to be argued with, and it has been.

The three tests a hallmark has to pass

Strong human evidence The criteria are the intellectual core of the whole thing. A candidate process must manifest with age. Experimentally aggravating it must accelerate aging. And experimentally ameliorating it must slow aging or extend healthy lifespan.^[2]

Notice how demanding the third condition is. Plenty of things change with age. Rather fewer accelerate aging when you make them worse. Very few have ever been improved in a way that measurably extended healthy lifespan in an animal. That is why the list is twelve items rather than two hundred, and it is a ready-made filter for any supplement claim you encounter.

No one really knows yet what the true causes are.

Why the list went from nine to twelve

The 2023 update added disabled macroautophagy, chronic inflammation and dysbiosis, bringing the count to twelve.^[3] None of the three was new as a concept. Each had simply accumulated enough evidence over a decade to satisfy the criteria that had excluded it earlier.

Autophagy was separated from proteostasis because its decline turned out to deserve its own line. Chronic low-grade inflammation, sometimes called inflammaging, earned inclusion on the strength of a large intervention literature. Dysbiosis arrived with the microbiome field. A framework that revises itself on evidence is behaving correctly.

What are the 14 hallmarks of aging?

There is no such published list. The two peer-reviewed frameworks are the nine of 2013 and the twelve of 2023. Meeting reports have floated further candidates, including mechanical properties of tissue and splicing dysregulation, and none of these has become canonical.

Where the number fourteen usually appears is on commercial pages that need a slightly bigger list to hang more products on. If a page presents fourteen as settled without naming the paper, that is the tell.

How the hallmarks connect

The framework groups them into primary damage, antagonistic responses to that damage, and integrative consequences that produce the phenotype. That structure matters because the hallmarks are not independent. Mitochondrial dysfunction feeds inflammation. Inflammation accelerates senescence. Senescent cells release signals that damage neighbors and deplete stem cell pools.^[4]

The consequence for anyone reading intervention claims is direct. Because everything is connected to everything, almost any compound can be described as targeting a hallmark. The description is nearly free. The demonstration is not.

There's no evidence that there is a single aging process that drives all of aging pathology.

Which hallmarks current interventions actually target

Deregulated nutrient sensing is the one with a real drug attached. Rapamycin inhibits mTORC1 directly, and it remains the compound with the most consistent lifespan extension record in animals, including mice started in late life.^[5] Our explainer on how mTOR inhibition works covers that pathway.

Cellular senescence has senolytics, an area with strong mouse data and thin human data, which we cover in the senolytic evidence review. Mitochondrial dysfunction and altered communication are the pitch for NAD precursors, where NAD levels do fall with age and the supplement case is far weaker than the biology implies.^[6] Disabled macroautophagy is where spermidine sits, with real animal work and a serious human absorption problem.^[7]

What actually touches the most hallmarks

Exercise. Reviews have argued that it attenuates most of the hallmarks simultaneously, through separate mechanisms rather than a single pathway: mitochondrial biogenesis, autophagy induction, lower chronic inflammation, better proteostasis, preserved stem cell function.

No compound comes close, and it is worth being blunt about why that comparison is uneven. Exercise has been studied for decades in enormous populations with hard outcomes. The supplements have mechanistic plausibility and mouse data. Those are different tiers of evidence, and the hallmarks framework, used properly, makes the difference visible rather than hiding it.

If they could bottle the effects of exercise, it would be the biggest thing in aging research that exists.

Using the framework to judge a claim

The next time a product says it targets a hallmark, apply the third criterion. Has improving this process, by this means, been shown to extend healthy lifespan in any organism? For rapamycin the answer is yes in mice. For most of the supplement shelf, the honest answer is that the compound changes a marker in a cell.

That is the practical value of the hallmarks of aging: not as a list to memorize, but as a standard of evidence someone already wrote down. Our review of what the longevity supplement evidence actually shows applies exactly that standard, compound by compound.

Frequently asked questions

What are the 12 hallmarks of aging?

Genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, disabled macroautophagy, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, altered intercellular communication, chronic inflammation and dysbiosis. The 2023 update added the last three plus disabled macroautophagy to the original nine.

What are the 14 hallmarks of aging?

There is no canonical list of fourteen. The peer-reviewed frameworks are the nine proposed in 2013 and the twelve proposed in 2023. Various meeting reports and commercial articles have floated additional candidates, and a page presenting fourteen as established is usually selling something adjacent to it.

Why did the list change from nine to twelve?

Because a decade of research strengthened the case for candidates that had not met the criteria in 2013. Chronic inflammation, dysbiosis and disabled macroautophagy accumulated enough evidence to qualify. The framework was designed to be revisable, and that revision is a sign of it working.

What makes something a hallmark rather than just a feature of aging?

Three tests. It should appear with age, experimentally worsening it should accelerate aging, and experimentally improving it should slow aging or extend healthy lifespan. That third test is the hard one and is why many plausible candidates never qualified.

Which hallmark do longevity drugs target?

Mostly deregulated nutrient sensing. Rapamycin inhibits mTORC1 directly, which is the clearest example of a compound aimed squarely at one hallmark. Senolytics target cellular senescence, and NAD precursors are aimed at mitochondrial dysfunction, with much weaker evidence in both cases.

Are the hallmarks causes of aging or symptoms?

The framework deliberately does not settle that. The three criteria require that intervening on a hallmark changes the trajectory, which implies causal contribution, but the hallmarks interact so heavily that separating cause from consequence for any single one is largely unresolved.

What is cellular senescence?

A state in which a damaged cell stops dividing permanently but does not die, and instead secretes inflammatory signals that disturb the tissue around it. It is both protective, as a brake on cancer, and harmful when senescent cells accumulate, which is why targeting it is more delicate than it sounds.

What habits age you faster?

Smoking, chronic sleep deprivation, sustained inactivity, excess alcohol, chronic psychological stress and diets that keep insulin and inflammation elevated. Each maps onto several hallmarks at once, which is part of why lifestyle effects are larger than any single supplement.

Can any intervention address all twelve?

Exercise comes closest. Reviews have argued it attenuates most hallmarks simultaneously through separate mechanisms. No drug or supplement does anything comparable, and any product claiming to cover all twelve is describing marketing rather than pharmacology.

Is telomere length worth testing?

Not really, for an individual. Telomere attrition is a real hallmark and consumer telomere tests have poor reproducibility and no established action attached to the result. Epigenetic clocks are more informative and still not clinically actionable.

How do the hallmarks connect to each other?

Densely. Mitochondrial dysfunction drives inflammation, inflammation accelerates senescence, senescence depletes stem cell pools, and nutrient sensing modulates almost everything else. That interconnection is why isolating one hallmark for treatment has been so much harder than describing it.

Does the framework predict how long someone will live?

No. It is a map of mechanisms, not a clinical tool. Nothing in it produces an individual prognosis, and no combination of consumer tests currently converts hallmark status into a reliable personal number.

Why does every supplement claim to target a hallmark?

Because the framework is respected, freely citable and written at the level of cell biology, which makes it easy to attach a mechanistic story to almost any compound. Meeting the first criterion is trivial. Meeting the third one, that improving it extends healthy lifespan, is where nearly everything fails.

Where should someone start reading?

The 2013 paper for the original architecture and the 2023 update for the current version. Both are open enough to read directly, and both are considerably more careful than the summaries built on top of them.