The Mystery of Premature Aging in Generation Z: The Rise in Cancer Among Young People and the Possible Role of "Whole-Body Aging"

The "Invisible Clock" Explaining the Rise in Cancer Among Young People

Cancer has long been considered a "disease that increases with age." This is because the number of cell divisions increases, genetic damage accumulates, and immune function and tissue repair capabilities decline.

However, in recent years, changes have occurred that are difficult to explain with this conventional wisdom alone. Certain cancers are increasing among adults younger than around 50 years old.

Globally, cancer diagnoses in individuals under 50 have increased from 1990 to 2019. The increase has been reported in multiple sites, including colorectal cancer, uterine cancer, kidney cancer, and breast cancer.

Can this be explained solely by the spread of screenings and advancements in diagnostic technology? Or are factors such as diet, obesity, lack of exercise, alcohol consumption, sleep, and environmental pollution collectively influencing this trend? Researchers have long sought the answer.

This is where "biological age" has begun to attract attention.

Unlike chronological age, which is counted from one's birthday, biological age refers to the estimated degree of aging of the body, inferred from blood tests, metabolism, inflammation, and organ function. Even among 40-year-olds, some may have a body condition closer to the average 35-year-old, while others may be closer to a 50-year-old.

Researchers wanted to know whether the increase in cancer among young people could be understood not just as a result of individual lifestyle habits but as an acceleration of aging accumulated throughout the body.

Generational Differences Revealed in Data from Over 150,000 People

A study published in the medical journal 'Nature Medicine' analyzed data from 154,169 individuals registered with the UK Biobank and 10,262 participants in the U.S. All of Us Research Program.

The research team estimated biological aging using multiple methods, focusing on "PhenoAge," which combines indicators related to albumin, creatinine, blood sugar, and inflammation in the blood.

The results showed a tendency for newer birth cohorts to have a higher biological age than the level predicted by chronological age.

In the UK data, the standardized age gap for those born between 1965 and 1974 was 23% higher than for those born between 1950 and 1954. In the U.S. data, those born between 1990 and 1999 showed a 92% higher value than those born between 1965 and 1969.

It is important to note that this does not mean that "those born in the 1990s had bodies that were 92% older."

The 92% figure is a comparison of statistically standardized indicators of the difference between biological age and chronological age, and cannot be simply converted to say "a 30-year-old was equivalent to 58 years old."

Sensational headlines might suggest that an entire generation is aging rapidly. However, in reality, it represents generational differences in estimated values calculated from multiple blood indicators.

Furthermore, Gen Z generally refers to those born in the late 1990s and beyond. Although the U.S. data includes those born in the 1990s, it is not accurate to lump them all together as the current Gen Z.

The essence of the study is not about specific generational labels but the "potential worsening of aging indicators in newer birth cohorts."

Those Biologically "Older" Had More Early-Onset Cancer

The research team further explored the relationship between differences in biological age and solid cancers occurring before the age of 55.

In the UK follow-up analysis, the group with the most advanced biological aging had a 15% higher risk of early-onset solid cancer compared to the group with the least advanced aging.

Analysis for each standard deviation increase in the age gap showed an 8% increase in the overall risk of early solid cancer. By site, the association was reported to be 57% higher for lung cancer, 17% for all gastrointestinal cancers, 14% for colorectal cancer, 25% for other gastrointestinal cancers, and 31% for uterine cancer.

These associations remained even after statistically adjusting for smoking, obesity, alcohol consumption, diet, exercise, socioeconomic conditions, medical history, and genetic predisposition.

However, this figure does not mean that "a 1-year increase in biological age results in a 57% increase in lung cancer."

The comparison is of relative risk when the estimated aging indicator changes by one standard deviation. In younger age groups, where the incidence rate is originally low, a large relative risk does not equate to an individual's absolute probability of developing cancer.

Independent data from the U.S. also showed the same direction of association between biological aging and early solid cancer. However, only 104 cases of early cancer were confirmed on the U.S. side, requiring additional verification for detailed conclusions by cancer type.

Differences in Aging Not Just "Overall" but Also by Organ

An interesting aspect of this study is that it examined not only the age of the entire body but also the aging of individual organs and tissues.

A method was used to analyze numerous proteins in the blood to estimate the condition of the immune system, adipose tissue, lungs, liver, and more.

Exploratory analysis suggested that those with more advanced immune system aging had more early-onset lung cancer, while those with more advanced adipose tissue aging had more early-onset colorectal cancer.

This suggests that not all cancers arise from the same aging pathway, but that different metabolic, inflammatory, and immune changes may be involved depending on the site where cancer occurs.

In the lungs, inhaled harmful substances, air pollution, chronic inflammation, and changes in immune response affect the tissue environment. In the colon, obesity, insulin resistance, inflammatory substances released from adipose tissue, and interactions with gut bacteria are considered.

While the study did not directly prove these pathways, the perspective of organ-specific aging may open new avenues for future personalized prevention.

Why is Aging Faster in Younger Generations?

The study showed generational differences but did not pinpoint a single cause.

Candidates include obesity and metabolic abnormalities from a young age, diets high in ultra-processed foods, prolonged sitting, lack of exercise, a shift to a nocturnal lifestyle disrupting the body clock, chronic sleep deprivation, psychological stress, air pollution, and environmental chemicals containing endocrine disruptors.

It is important not to simplistically attribute these to "young people's lack of self-management."

There are many factors that are difficult to change by individual will alone, such as urban environments overflowing with affordable, long-lasting food, jobs that assume prolonged sitting, digital culture demanding connectivity until late at night, unstable employment and rising housing costs, workplaces where rest is hard to take, and cities that are not conducive to exercise.

Biological age can be thought of as a "cumulative score" that these numerous factors have etched into the body over a long period.

Even if it is difficult to measure each cause individually, the strength of this indicator lies in its ability to collectively capture results manifested in inflammation, metabolism, kidney function, and immunity.

On the other hand, this strength can also be a weakness.

A high biological age does not reveal what the cause is. There may be a possibility that obesity affects both aging indicators and cancer risk, or that a small cancer before diagnosis changed blood indicators, making the body appear older.

It is not possible to determine causation from correlation.

Four Reactions Spread on Social Media

When the study was reported, it attracted significant attention on social media platforms like Reddit and LinkedIn.

However, public posts are written voluntarily by users and do not represent a survey of public opinion. What can be confirmed are the noticeable trends in reactions within the publicly available discussions.

1. "More Convincing than Surprising"

The first noticeable reaction was that people found the results more convincing than surprising, considering their current lifestyles.

Surrounded by sleep deprivation, sedentary lifestyles, processed foods, economic anxiety, a digital environment with constant notifications, and work stress, it is not surprising that young people's bodies are wearing out quickly.

Some people who experience long working hours and unstable employment pointed out that "this is not just a medical issue but also an environmental and policy issue."

The argument is that it is necessary to review not only treatment after illness but also the working styles, food environments, and urban environments that harm health.

2. Voices Suspecting COVID-19 Infection and Aftereffects

The second reaction was suspicion of a link to COVID-19 infection and its aftereffects.

Posts suggested that repeated infections and chronic inflammation might be accelerating aging, with some individuals feeling a sudden decline in physical strength after infection.

However, this study did not examine COVID-19 as a primary factor. The observed generational differences cannot be fully explained by the pandemic or post-infection aftereffects alone.

It is necessary to distinguish between the impressions and hypotheses on social media and the conclusions confirmed by research.

3. Skepticism About Measurement Methods and Participant Bias

The third reaction was cautious opinions about the research methods.

Biological age is not a directly measurable value like blood pressure; it is calculated by inputting multiple test values into an algorithm. The results may vary depending on how the model is constructed, and its significance in clinical settings is not yet fully established.

It is known that participants in the UK Biobank tend to be healthier and wealthier than the general population.

Additionally, in older generations, there is a possibility of "survivor bias," where unhealthy individuals die before the study begins, leaving only relatively healthy individuals as participants. In such cases, younger generations may appear relatively unhealthy.

In the UK analysis, 92% of the subjects were white, and the results may not be directly applicable to regions with different races, incomes, healthcare systems, food cultures, and environments.

There were voices on social media questioning whether the same trends are seen in Asia, Africa, Latin America, and other regions. The research paper itself acknowledges the limitations of generalization and calls for revalidation in more diverse populations.

4. Expectations for Preventive Medicine

The fourth reaction was the expectation that biological age could be utilized in future preventive medicine.

Posts from healthcare professionals and researchers pointed out that if biological age is sufficiently validated, it could help identify high-risk individuals who have been overlooked based on chronological age and family history alone.

In the future, if it becomes possible to determine from blood data that "the immune system related to the lungs is older than average" or "adipose tissue aging is advanced," it might be possible to individualize screening timing and lifestyle interventions.

However, at present, this is still in the research stage, and it is not a situation where screening methods can be changed based solely on biological age.

What the Research Has Not Proven

For high-profile research, it is necessary to confirm not only "what has been discovered" but also "what has not been discovered."

Firstly, this study is observational and does not prove that biological aging directly causes cancer. There may be a third factor that advances both aging and cancer.

Secondly, the measurement of biological age was essentially at a single point in time.

It is unknown who started aging rapidly at what age, or whether cancer risk decreases in individuals whose numbers decreased due to improved living environments. Research that follows individuals over several years and repeatedly measures the same indicators is needed.

Thirdly, we are not at the stage where "taking a biological age test will tell you if you will get cancer."

There are various methods for commercially available aging tests, and they are not necessarily the same as the indicators used in this study. It is not appropriate to become overly fearful if the numbers are high or to skip screenings and medical visits if they are low.

Fourthly, generational averages are not individual destinies.

Even if average values worsen in a new birth cohort, there are significant individual differences within the same generation. Genetics, living environment, income, region, sleep, diet, exercise, infection history, and access to healthcare can greatly affect one's physical condition.

What Should We Take Away?

This study should not be used for generational criticism, such as "Gen Z is unhealthy."

Rather, the question is what modern society is accumulating in young bodies.

If people cannot get enough sleep, find it difficult to secure time for healthy food and exercise, and cannot easily escape harmful substances and chronic stress, it is not a problem that can be solved by individual effort alone.

At the individual level, traditional preventive measures such as quitting smoking, reducing alcohol consumption, regular exercise, managing weight and blood sugar, a diet including vegetables and fiber, and getting enough sleep remain realistic options.

If there are persistent bloody stools, unexplained weight loss, prolonged cough, irregular bleeding, or persistent pain or lumps, it is important not to assume "it's okay because I'm young" and to consult a medical institution.

At the societal level, there is a need for price policies that make it easier to choose healthy foods, work environments where people can sleep, walkable cities, measures against environmental chemicals and air pollution, and a medical system that does not underestimate the symptoms of young people.

If biological aging truly explains part of early-onset cancer, prevention does not end within the consultation room.

The body has a clock separate from the calendar.

What is advancing the hands of that clock—diet, stress, environment, or a combination of multiple factors—is still in the process of being elucidated.

Nevertheless, this study provided a perspective that views early-onset cancer not as an "unfortunate exception" but as a bodily change accumulating from an early stage in life.

The important thing is not to incite fear.

It is to refine measurement methods, verify them in diverse populations, identify causes, and reduce modifiable factors from both societal and individual perspectives.

Beyond the provocative words "young people are aging," there is the potential for medical care