The Hallmarks of Ageing: What Actually Makes Us Age

We talk about ageing as if it were one thing — a single, vague slide from young to old that simply happens to us. It feels inevitable and a little mysterious, which is exactly why so much "anti-ageing" marketing gets away with so much. But over the last decade, ageing research has done something quietly powerful: it has broken that one mysterious thing down into a defined, named set of biological processes. They're called the hallmarks of ageing, and understanding them is the single most useful lens for thinking clearly about healthy ageing — including which interventions are worth your attention and which are noise.

This is a plain-language guide to what the hallmarks are, why they matter, how they connect to each other, and — most importantly — what you can actually influence.

Ageing isn't just "wear and tear"

The instinctive way to think about ageing is mechanical: like a car or a pair of shoes, the body simply wears out with use. It's an intuitive picture, but it's incomplete. A great deal of ageing is not passive wear at all — it's the slow accumulation of specific kinds of biological damage, and the body's own responses to that damage, playing out at the level of cells and molecules.

In 2013, a landmark paper in the journal Cell set out to organise this messy picture. Its authors proposed a framework of nine "hallmarks" — biological processes that consistently show up as we age across many different organisms ¹. The idea caught on because it gave the whole field a shared map: instead of thousands of disconnected findings, here was a structured way to say these are the common denominators of getting older.

What makes something a "hallmark" rather than just a feature of old age? Broadly, researchers look for three things: it should appear progressively with age, making it worse should accelerate ageing, and counteracting it should slow ageing down or improve health in later life ¹. That last criterion is the hopeful one — it means these aren't just descriptions of decline, but potential targets.

The hallmarks, grouped so they make sense

Listing twelve biological mechanisms is a fast way to make eyes glaze over. It's far more useful to understand them in the three groups the original framework used, because the groups tell a story ¹.

1. The primary hallmarks — the damage that accumulates. These are the root sources of trouble; they're unambiguously harmful and they pile up over time:

• Genomic instability — damage to your DNA from everyday metabolism, radiation and chemicals, plus the gradual fraying of the systems that repair it.
• Telomere attrition — the protective caps on the ends of chromosomes (telomeres) shorten each time a cell divides, like the plastic tips wearing off a shoelace.
• Epigenetic alterations — the chemical "annotations" that tell genes when to switch on and off drift out of tune with age, so the right genes fire at the wrong times. Reading these marks is how an epigenetic clock estimates your biological age.
• Loss of proteostasis — the cell's quality-control system for folding and clearing proteins falters, letting damaged proteins build up.

The 2023 update added a close cousin here: disabled macroautophagy — a decline in the cell's recycling system, which normally digests and reuses worn-out parts ².

2. The antagonistic hallmarks — helpful in youth, harmful in excess. These are responses that are protective at the right dose but become damaging when they're chronically over- or under-active:

• Deregulated nutrient-sensing — the pathways that read how much food and energy is available (and decide whether to grow or conserve) become dysregulated.
• Mitochondrial dysfunction — the tiny "power plants" inside cells become less efficient, producing less clean energy and more cellular stress. This is the cellular-energy angle behind much of the longevity conversation — the reason molecules like NAD+ attract so much interest (we look at the honest evidence in What is NAD+, and can it really slow ageing?).
• Cellular senescence — cells that stop dividing but refuse to die linger as so-called "zombie cells", releasing inflammatory signals into the tissue around them.

3. The integrative hallmarks — the consequences you actually feel. These emerge when the damage above overwhelms the body's compensation, and they're the ones that show up as the visible, functional signs of ageing:

• Stem-cell exhaustion — the body's reservoirs of repair-and-replace cells run down, so tissues regenerate more slowly.
• Altered intercellular communication — the chemical "conversations" between cells become noisier and more inflammatory.

The 2023 framework formally added two more integrative hallmarks: chronic inflammation and dysbiosis (an unhealthy shift in the gut microbiome) ².

From nine to twelve — a living framework

One of the most reassuring things about this framework is that it's honest about being unfinished. A decade after the original paper, the same authors published an update — Hallmarks of aging: An expanding universe — that grew the list from nine to twelve, adding disabled macroautophagy, chronic inflammation and dysbiosis as the science matured ². Researchers continue to debate which other candidates might eventually qualify ⁴.

That expansion matters for one detail in particular. Chronic, low-grade inflammation — the process nicknamed "inflammaging" — was promoted to a hallmark in its own right. In other words, the inflammation story isn't a side note to ageing; it's now recognised as one of its core drivers. We explore that specific process in depth in Chronic Inflammation and Ageing.

Why this matters: the hallmarks talk to each other

Here's the insight that changes how you read every "anti-ageing" headline: the hallmarks are not a checklist of separate problems. They're deeply interconnected, each one feeding and amplifying the others ². Mitochondrial dysfunction generates stress that damages DNA. Senescent "zombie cells" pump out inflammatory signals that worsen chronic inflammation. Chronic inflammation, in turn, accelerates stem-cell exhaustion. Pull on one thread and the whole web moves.

This is precisely why the framework has been so valuable — and why it's such a useful filter for hype ⁴. There is no single "master switch" of ageing waiting to be flipped. Any product promising to reverse ageing by targeting one molecule is, almost by definition, telling you a story that's too simple. The real picture is a system, and systems respond to broad, consistent inputs far more than to single silver bullets.

What you can actually influence

If the hallmarks were purely about damage you can't control, this would be a gloomy article. They're not — and this is the genuinely encouraging part. Several hallmarks are strongly shaped by how you live, and the most powerful interventions we have don't target one hallmark; they nudge many at once.

The clearest example is physical activity. Regular exercise has been described in the research literature as acting like a "polypill" for ageing — a single habit that favourably influences a remarkable range of the hallmarks at the same time, from mitochondrial function and nutrient-sensing to inflammation and intercellular communication ³. It is, by a wide margin, one of the most evidence-backed pro-longevity things a person can do, and it costs nothing.

The rest of the list will look familiar, because the foundations of healthy ageing are consistent across almost every area of medicine:

• Move regularly. The single most broadly protective lever, touching many hallmarks simultaneously — and consistency matters far more than intensity ³.
• Eat mostly whole foods. Dietary patterns rich in vegetables, fruit, whole grains, legumes, fish and healthy fats support nutrient-sensing pathways and a healthier gut microbiome — two of the twelve hallmarks directly.
• Protect your sleep. Sleep is when much cellular repair and clean-up happens; chronically short or poor sleep undermines several hallmarks at once.
• Manage chronic stress. Sustained stress keeps inflammatory signalling switched on — and chronic inflammation is now a hallmark in its own right.
• Don't smoke. Smoking is a direct, powerful driver of DNA damage and inflammation — two root hallmarks at the same time.

None of this is glamorous, and none of it is new. But measured against the hallmarks, it's clear why these basics work: they act on the underlying biology of ageing broadly and consistently, which is exactly what a system of interconnected processes responds to.

Where regenerative medicine fits

The hallmarks framework also explains why so much serious longevity research has moved towards regenerative approaches. Two hallmarks in particular — stem-cell exhaustion and the broader loss of the body's capacity to repair itself — point to the same problem: with age, tissues regenerate more slowly and less completely. Regenerative medicine is the field trying to understand and support that repair capacity rather than simply manage symptoms. We cover what that does and doesn't mean, honestly, in our guide to regenerative medicine.

What we see at the clinic

People often come to us looking for the anti-ageing thing — the one infusion, supplement or test that will turn the dial. We understand the appeal, but the hallmarks framework is exactly why we answer the way we do: ageing is not one process with one switch, it's a dozen interconnected ones, so there is no single intervention that credibly addresses it. What genuinely helps is broad and consistent — the foundations done well, applied over years, and personalised to the individual. Where it adds value, thoughtful measurement and physician-led care can help track and tailor that plan. But the plan itself is built on the basics, not as a way around them — and anyone selling a shortcut around them deserves a healthy dose of scepticism.

Common questions

How many hallmarks of ageing are there? The original 2013 framework defined nine. A 2023 update expanded it to twelve, adding disabled macroautophagy, chronic inflammation and dysbiosis. It's an actively evolving framework, so the number may grow again as the science matures.

Can ageing be reversed? In the lab, researchers have reversed specific hallmarks in cells and animals, which is genuinely exciting — but that is a long way from a proven way to reverse ageing in people. The realistic and honest goal today is to slow the processes and extend healthspan — the years lived in good health — not to find a reversal pill. Be very cautious of anyone claiming otherwise.

Is there a single most important hallmark? No — and that's the central point. They're interconnected and reinforce one another, so no single one is "the cause" of ageing. Chronic inflammation is often described as a connective thread because it links to so many of the others.

What's the single best thing I can do today? Regular physical activity. It influences more hallmarks at once than almost any other single habit, and it improves sleep, weight, mood and inflammation along the way.

Are anti-ageing supplements worth it? Mostly far less than their marketing suggests. Because ageing is a system of interconnected processes, single-molecule supplements rarely live up to the promise. A consistent whole-lifestyle pattern is far better supported by the evidence than any individual product.

Key takeaway

Ageing isn't one vague, inevitable thing — it's a defined set of biological processes, the hallmarks of ageing, that scientists can now name, measure and study. There are twelve in the current framework, they're deeply interconnected, and two of them — chronic inflammation and stem-cell exhaustion — tie ageing directly to the topics of inflammation and regenerative medicine. The most empowering conclusion is also the most down-to-earth: because the hallmarks form a connected system, the things that influence many of them at once are the everyday foundations — moving, eating well, sleeping, managing stress and not smoking — done consistently. There's no master switch, but there's a great deal you can do.