For at least thirty years, cancer statistics have told a story that runs counter to what one would expect from an increasingly efficient and up-to-date healthcare system: cancers diagnosed at an early age—that is, before age 50—are on the rise. Between 1990 and 2019, cancer diagnoses among people under 50 rose by 24% globally. For certain types of cancer, such as colorectal cancer, people born in the 1990s face at least four times the risk compared to those born in the 1960s in countries such as Australia, Canada, the United Kingdom, and the United States.
The study, led by Ruiyi Tian and Yin Cao of Washington University School of Medicine in St. Louis and published in *Nature Medicine*, attempts to explain why. The bodies of younger generations appear to age biologically faster than their chronological age would suggest, and this discrepancy is linked to a higher risk of developing cancer at a young age.
What does “biological age” mean, and how is it measured?
The researchers analyzed blood samples from 154,169 people under the age of 55 enrolled in the UK Biobank, a large British biomedical database, and calculated their biological age using PhenoAge, an algorithm that estimates how “worn out” the body is by analyzing nine blood parameters such as creatinine, glucose, and C-reactive protein.
The difference between biological age and actual age is called age gap: the wider this gap, the more the body shows signs of wear and tear beyond what is expected for that age. The most significant finding concerns generational trends: when comparing those born between 1965 and 1974 with those born between 1950 and 1954, the authors found a standardized age gap that was 23% higher. Women, in particular, start with a lower age gap than men, but over time they see it grow more rapidly, to the point of approaching men’s levels in more recent generations.
The same trends were confirmed, based on a smaller sample (10,262 people), in theAll of Us Research Program, a U.S. government biomedical research project that collects health data and biological samples from more than 450,000 American adults.
It’s not just a matter of genes
The key point, according to the authors, is thatthe age gap isnot simply a reflection of a predisposition encoded in DNA, but appears to depend on factors related to lifestyle and environmental exposures accumulated over the course of a lifetime. The study explicitly cites factors such as early-onset obesity, poor diet, prolonged physical inactivity, exposure to air pollutants and pervasive chemicals, as well as disrupted circadian rhythms, as possible drivers of this accelerated aging in more recent generations.
A figure to be treated with caution
At the same time, the researchers themselves point out the study’s limitations: it is an observational study and focuses on populations in the United Kingdom and the United States, so its findings may not necessarily be applicable elsewhere. Nevertheless, it remains an important piece of a puzzle that the field of oncology has been trying to solve for years: understanding why, at a time when cancer prevention is more widespread than ever, more and more people are being diagnosed with cancer before the age of 50.
