Why ageing is multi-system

Most of us think of ageing as something that happens later, and in parts. Joints first, then eyesight, then memory. One organ, then the next.

The research tells a different story. Ageing starts early, and it happens across the whole body. And the pressures of modern life seem to work the same way.

The study

The Dunedin Study in New Zealand has followed a group of people born in 1972 and 1973 since birth. In 2015, researchers led by Daniel Belsky asked a simple question: can we measure how fast young adults are ageing?¹

They measured 18 biomarkers in 954 participants at ages 26, 32 and 38. The markers covered the heart and blood vessels, metabolism, the lungs, the kidneys, the immune system, the teeth and gums, and DNA itself (telomere length).

954 people followed from 26 to 38 · 18 biomarkers across the body's systems · 12 years of change measured per person

What they found

By 38, the participants were all the same age on paper, but not in their bodies. Their biological ages spanned roughly three decades, and the speed at which they were ageing varied widely.¹

The people ageing faster weren't faster in one system and normal in the rest. The changes showed up across many systems together. They also performed worse on tests of physical function, and looked older in photographs to strangers.

Ageing isn't one clock in one organ. It's many systems changing together, and it starts years before we notice.

The team later turned this into a single measure of the pace of ageing, readable from a blood sample. Faster pace predicted more illness, disability and earlier death in other groups of people.² Ageing, it turns out, can be measured as a speed.

Down to the cell

If the Dunedin Study shows ageing across the body, cell biology shows what drives it. In 2013, and again in an expanded 2023 review, scientists grouped the processes behind ageing into 12 hallmarks, including DNA damage, telomere shortening, mitochondrial decline, chronic inflammation and changes to the gut microbiome.³

The hallmarks are connected. A change in one tends to affect others, which is part of why ageing shows up in many places at once. (Read: The 12 hallmarks of ageing, in plain English.)

Modern life rarely hits one system at a time

Here's the part that surprised me most. The pressures of everyday modern life seem to follow the same pattern as ageing itself. They don't stay in one place.

• Sleep and the body clock. In shift workers, and in lab studies that shift people's sleep and light, a mistimed body clock affects blood sugar control, energy use, the immune system, blood pressure and heart rhythm, all at once.⁴
• Short sleep and immunity. People who sleep too little around the time of a vaccination make fewer antibodies.⁵ Three or more nights of restricted sleep raise markers of inflammation in the blood.⁶
• Stress and energy. Most studies in a systematic review found psychological stress affected mitochondria, the structures that produce energy inside our cells.⁷
• Sitting. Long periods of sitting have their own physiology, affecting metabolism and blood vessels. It isn't simply the absence of exercise.⁸
• The gut. The gut communicates with the brain through nerves, immune signals, hormones and metabolites.¹¹ What happens in one rarely stays there.

A pattern runs through these findings. The same few hubs keep appearing: inflammation, the body's clock, metabolism, the stress response and the gut. Pull on one and the others move.

A note of honesty: much of this research shows links, not proof of cause, and it comes from different kinds of studies. But the direction is consistent. "Energy", "sleep", "gut" and "stress" are better understood as connected systems than as separate problems.

Ageing as resilience loss

Put the pieces together and a picture emerges. A young body absorbs a bad night, a stressful week or a heavy meal and returns to balance. Over decades, that recovery becomes slower and less complete.

Researchers describe one version of this as inflammaging: a low-grade inflammation that creeps up with age, alongside a gradually less responsive immune system.⁹ More broadly, ageing is increasingly described as a slow loss of resilience across many systems, rather than the failure of one organ.¹⁰

It's a more hopeful framing than it sounds. Resilience isn't fixed. Much of what supports it happens daily.

What it means day to day

The practical message isn't alarming. It's that the habits that matter most look after the whole body, consistently, over years: how you eat, move, sleep and recover. Because everyday pressures act on many systems at once, so do the everyday choices that ease them. Consistent sleep timing, regular movement, breaking up long sitting, a varied diet.

This is the thinking behind 4VIA: health you notice day to day, and longevity you build over years, are the same body, working as one network. It's why we built 4VIA around the body's systems rather than a single pathway. You can read how the formula is mapped on our Science page.