Why young people are getting cancer more often: scientists have found an unexpected answer
Cancer, once considered a disease of the elderly, is increasingly being found in people under 50 — with a particularly notable rise in colorectal cancer among younger individuals. A new study in the journal Nature Medicine offers an unexpected explanation: the bodies of younger generations may be aging slightly faster than those of their parents at the same age. The authors immediately emphasize that this is early-stage research and does not prove a direct causal relationship, although it does reveal important insights.
How biological age differs from chronological age
Chronological age is straightforward: it’s the number of years since birth. But biological age can vary significantly between two people born in the same year. This term refers to a whole set of indicators — markers on DNA and substances in the blood that show how worn out the body actually is.
It is measured using so-called “aging clocks” — algorithms that use test results to determine whether the body is behaving older or younger than its chronological age. Understanding why two people of the same age can age at different rates is aided by new biological clocks.
The main idea is simple: one person at 35 may have a “body” of a 30-year-old, while another may have one of a 40-year-old. It is precisely this difference, which researchers called the age gap, that became the focus of the new study.
Why the 1990s generation is aging faster than their parents
Scientists applied this approach to large biobanks — databases containing genetic and medical data from tens of thousands of people. In the American All of Us program, which included about 10,000 participants, a notable pattern emerged.
People born between 1990 and 1999 had an age gap approximately 0.92 standard deviations higher than those born between 1965 and 1969. In plain language: the younger generation’s biological age, on average, outpaced their chronological age slightly more than it did for their parents at a comparable age.
The main calculations were based on a tool called PhenoAge — one of the “aging clocks” that estimates age using blood markers. Another algorithm, the Klemera-Doubal method, showed a similar pattern, though weaker. This means the trend was not dependent on a single measurement method.
Meanwhile, the question of why millennials get cancer more often than their parents also still lacks a definitive answer.
The strongest association between age gap and early-onset cancer was found for lung, gastrointestinal, and uterine cancers
How accelerated aging was linked to early-onset cancer
The most important part of the study was the attempt to link this age gap to cancer risk. In the UK Biobank, scientists found that participants with a larger age gap were more likely to develop early-onset cancer — meaning malignant tumors in solid tissues rather than “liquid” blood cancers.
The strongest association was found for lung, gastrointestinal, and uterine cancers. When participants were divided into three groups by biological age, people in the “oldest” group had an approximately 15% higher risk of early-onset cancer compared to the “youngest” group.
To dig deeper, the authors used a model that estimates organ-specific aging based on blood proteins. It turned out that an immune system that had “aged prematurely” was associated with a risk of early-onset lung cancer, while prematurely aged adipose tissue was associated with a risk of early-onset colorectal cancer. Incidentally, age isn’t the only factor affecting cancer risk — tall people also get cancer more often.
One type of cancer increasingly found in people under 50 is breast cancer.
Accelerated aging and early-onset cancer: a real pattern or a data error
The authors explicitly call the study a “proof of concept” — meaning a test of an idea, not a definitive answer. Does this mean younger generations are aging faster and that’s exactly why they get cancer more often? Maybe, maybe not.
There are several important caveats. First, the pattern needs to be confirmed using other data and populations. Second, biological age tests are relatively new, and different tests can produce completely different results for the same person. This raises the question of what a single score even means.
An independent expert, Cambridge University biostatistics professor Stephen Burgess, who was not involved in the study, suggested that the observed difference between younger and older participants might be related to how the PhenoAge test was originally calibrated. To verify this, a detailed examination of how the scores are calculated is needed, and whether they distorted the assessment.
What accelerated aging and early-onset cancer risk mean for ordinary people
The main thing not to do after hearing such news is rush to take a biological age test and panic over the number. At the individual level, these tests are still unreliable, and the authors themselves acknowledge that PhenoAge requires additional validation for cancer risk assessment. Meanwhile, long-known risk factors remain relevant: a sedentary lifestyle is also linked to faster bodily aging and the risk of certain types of cancer.
Far more valuable is the fact that science is gaining a new tool to understand why cancer is getting younger. In observational studies on large datasets, it’s difficult to separate cause from effect: a found association does not yet prove that one caused the other. But even so, the approach is useful: either as a way to monitor population health, or as a clue about the mechanisms that trigger cancer.
The rising number of cancer diagnoses among young people is a real and alarming trend that scientists have not yet fully explained. This study doesn’t put a final period on the matter but rather outlines a direction: perhaps the key to the mystery lies not in a single “harmful factor” but in how the body of an entire generation ages. What needs to be investigated further is whether the pattern holds up in other populations and whether “aging clocks” can withstand more rigorous scrutiny.
