Cancer has long been associated with ageing. But in recent years, more adults are being diagnosed with cancer at younger ages, prompting scientists to investigate what could be driving the trend.

A new study led by researchers at Washington University School of Medicine in St Louis suggests that faster biological ageing may be one piece of the puzzle.

The researchers found that people from more recent generations tended to have biologically older bodies than people from earlier generations at the same chronological age. They also found that greater biological age acceleration was associated with a higher risk of early-onset cancer.

The findings were published in Nature Medicine.

When biological age does not match your actual age

Chronological age is simply the number of years a person has lived. Biological age, however, reflects how old the body appears based on changes in cells, organs, metabolism and other physiological systems.

According to the researchers, cancer risk increased as the gap between biological and chronological age grew.

People born in more recent generations generally showed larger gaps, meaning their bodies appeared biologically older despite being the same chronological age as people born in earlier generations.

The researchers say this generational shift could help explain part of the rise in cancer among younger adults.

The effects were not the same across every part of the body. An immune system that appeared biologically older was associated with a higher risk of early-onset lung cancer, while older-appearing fat tissue was linked to early-onset colorectal cancer.

Younger generations show signs of faster ageing

The researchers analysed health and biological data from more than 154,000 young adults in the UK Biobank and more than 10,000 participants in the US National Institutes of Health’s All of Us Research Program.

To measure biological ageing, they looked at both ageing across the whole body and ageing in specific organs and biological systems.

For overall ageing, the team used established measures such as PhenoAge and the Klemera-Doubal Method, along with a metabolomic age score based on age-related changes in metabolism.

They also examined blood proteins associated with individual organs to estimate organ-specific biological age.

The differences were visible in both the UK and US populations.

In the UK data, people born between 1965 and 1974 had systemic ageing that was 23% of a standard deviation higher than those born between 1950 and 1954, after accounting for chronological age.

The difference was even larger in the US data. People born between 1990 and 1999 had systemic ageing that was 92% of a standard deviation higher than those born between 1965 and 1969.

In simple terms, younger generations tended to have slightly older biological profiles than older generations when compared at the same age.

Faster biological ageing linked to cancer risk

The researchers then examined whether the differences in biological ageing were associated with early-onset cancer.

They found that greater systemic ageing among younger participants was associated with an 8% higher risk of early-onset solid cancers. The strongest links were found for lung, gastrointestinal and uterine cancers.

Participants with the most advanced systemic ageing had a 15% higher risk of early-onset solid cancer compared with those with the least advanced ageing.

The association remained even after researchers accounted for inherited genetic cancer risks and genetic susceptibility to accelerated ageing.

Looking at individual biological systems also revealed more specific links. Advanced immune-system ageing was associated with a higher risk of early-onset lung cancer, while accelerated ageing of fat tissue was linked to early-onset colorectal cancer.

What is causing younger people to age faster?

The researchers caution that there is still no definitive answer to why early-onset cancers are becoming more common.

Previous research by Cao’s team has examined several factors that may influence cancer risk, including obesity, metabolic problems, alcohol consumption, sedentary behaviour, poor diet and caesarean delivery.

However, no single factor appears to explain the wider increase in cancer among younger adults.

The new research is part of Team PROSPECT, an international project supported by Cancer Grand Challenges, which brings together researchers from different fields to investigate why early-onset cancers are becoming increasingly common.

Researchers are now examining how environmental, lifestyle and social changes may leave lasting biological effects on the body, potentially accelerating ageing or making certain people more vulnerable to disease.

The long-term goal is to identify people at higher risk of cancer while they are still healthy. If researchers can better understand these biological changes, screening and prevention could eventually begin earlier and be tailored to an individual’s risk.

As researchers continue to investigate why cancer is appearing earlier in life, biological ageing could offer another important clue to what is happening inside the bodies of younger generations.