What is aging? Disagreement among researchers about the definition and causes

What is aging? Disagreement among researchers about the definition and causes

Researchers who aging study, disagree on almost everything - including what exactly aging is, whether it is a disease and when it begins. This emerges from a survey of around 100 scientists working in this area.

A central goal of aging research is to help people live longer, healthier lives. Yet the exact causes of aging and effective methods to slow or reverse it remain elusive. For scientists to address these challenges, they need to speak a common language, says Alan Cohen, who studies aging at Columbia University in New York City. “There doesn't have to be a perfect consensus, but we have to clarify things clearly,” he explains.

Vadim Gladyshev, another researcher in the field at Harvard Medical School in Boston, Massachusetts, and his colleagues agree. They decided to survey participants at an international aging conference in Newry, Maine, in 2022 to better understand the views of those researching the topic. Respondents included emerging researchers, established scientists and industry professionals. The results are described today in PNAS Nexus 1.

Most researchers are clear about the definition of aging - but their perspectives often don't agree with those of others, says Gladyshev. “In this field, people joke that there are more theories than people.” Despite these diverse views, Gladyshev was surprised at the scale of the problem.

The latest results echo those of a similar survey of 37 researchers in 2019 conducted by Cohen and his colleagues 2. Now it's "undeniably clear that there is tremendous disagreement," Cohen says.

What is aging?

When asked to describe aging, a third of respondents viewed aging as a loss of function over time, from cellular damage to a decline in overall health and fitness. Others saw aging as one gradual accumulation of harmful changes. Not all respondents associated aging with negative consequences; some described it as a state – reversible or not – or a continuation of development. Others looked at the issue from a demographic perspective and simply described aging as one increased chance of dying.

Questions about the causes of aging also yielded a wide range of answers, from damage accumulation to evolutionary constraints, and from changes in the regulatory system to deterioration in repair mechanisms. Some admitted that they do not know what underlies aging.

Researchers also disagree about whether aging is a disease. More than a third of respondents said it was a disease, 38% denied it, and the remaining 28% remained neutral. Cohen is against describing aging as a disease because it implies that it is something that needs to be eliminated, although many researchers in the field do so to some extent work towards this goal.

For Gladyshev, the answer to this question is more complicated. “Aging is not a disease, but it is not not a disease either,” he says. He sees many diseases as ultimately accelerated aging that occurs in specific organs or the body as a whole.

When does aging begin?

Respondents generally agreed that aging begins early in life, but could not agree on how early.

Some said the process begins before conception, when eggs and sperm are produced. According to this theory, people whose parents are older when they conceive are more advanced in age, Cohen says. The problem with this view is that it theoretically goes back forever into the past. Cohen believes that aging begins from the moment the egg and sperm meet - at conception.

However, others believe that aging begins on the day of birth. Some said it starts with the onset of puberty. Still others believe that aging only begins when the body stops developing, when a person is in their early twenties, or a few years later when the body reaches its peak performance - mid-twenties.

Ultimately, Gladyshev says, the wide variety of answers reflects the many unknowns in the field. He expects rapid progress in defining aging, including the development of biomarkers to do that biological age to pursue. “It’s a time of opportunity.”

1. Gladyshev, V.N. et al. PNAS Nexus https://doi.org/10.1093/pnasnexus/pgae499 (2024).

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2. Cohen, A.A. et al. Mech. Aging Dev. 190, 111316 (2020).

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