Credit: Simon Prades
The study of ageing has shifted from a niche pursuit to a major area of research. Over the past two decades, scientists have flooded the field, determined to unlock the secret to a longer, healthier life. “Various people have started to think we could intervene in the ageing process and extend lifespan. [The field] has really exploded because of that view,” says Alan Cohen, a biologist at Columbia University in New York City.
But even as interest grows, scientists have yet to reach consensus on fundamental concepts in biological ageing, Cohen says. There is no widespread agreement on what ageing is or when it begins, or what the goal should be in investigating it. “There are people like me who think we can’t intervene — and even if we could, we shouldn’t — to people at the far end of the extreme who say we should make humans immortal and every moment we delay is equivalent to murder,” Cohen says. “Serious scientists are at every point along that spectrum.”
Nature Index 2025 Ageing
A key contention is whether ageing should be considered a disease. As Richard Faragher, a biogerontologist at the University of Brighton, UK, puts it, if a disease is defined as something abnormal, then ageing does not count. But if a disease is defined as something that is preventable, treatable and able to be slowed down, then ageing is a disease.
Scientists, doctors and philosophers have pondered this question for centuries, but as more countries confront the realities of an ageing population, the debate has taken on new urgency, and it has the potential to influence everything from the direction of research to how older people are treated in society. “This is the early phase of an incredibly rapidly growing field,” says John Beard, an epidemiologist at Columbia University. “I think people are open to thinking about it in new ways, if a new way makes sense.”
Is ageing a disease?
The concept of what is and isn’t a disease has changed over time. For example, before the 1960s, developing high blood pressure in older age was not considered a problem, says Faragher. “Now, we know that your blood pressure going through the roof is not benign.” Crucially, he adds, labelling high blood pressure, or hypertension, as a disease brought both funding and research attention to find treatments for it. “Things only start to get studied when they become problems.”
Some people like to think of ageing as “a kind of optimal, almost benign decline” with certain diseases overlaid, says Faragher. But he and some other researchers argue that this oversimplifies things, that ageing and disease aren’t necessarily separate, and that treating them as such can hold back progress on understanding and managing the process. Ageing “is inseparable from pathology”, says Faragher. He points to senescent cells — damaged cells that behave in harmful ways and accumulate with age — which not only contribute to conditions such as heart disease, osteoporosis and cognitive impairment, but are also linked to hallmarks of ageing such as grey hair and wrinkles. In animal studies1, deleting these cells leads to “dramatic increases” in health and lifespan, Faragher says, which suggests that this aspect of ageing “is both treatable and reversible”.
James Pacala, an academic geriatrician at the University of Minnesota in Minneapolis, says that for some researchers, the ideal scenario in ageing science is to find “some common cellular and molecular denominator that leads to all of the declines we see with ageing”. Cohen says it’s unlikely, however, that a single cause could explain ageing, because millions of factors probably contribute to the body gradually losing its ability to stay organized and function properly. Faragher agrees that there probably isn’t one single mechanism of ageing, but that there is a small set of key mechanisms — such as a build-up of senescent cells — that act together as a loose network and cause many age-related diseases as well as ageing itself.
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