People born in the 1980s and 1990s are biologically older than their parents and grandparents were at the same chronological age — and that faster biological aging is associated with a measurably higher risk of developing cancer before 55, according to a large study published June 22, 2026 in Nature Medicine by researchers at Washington University School of Medicine in St. Louis.
The finding may help explain a puzzle that has unsettled oncologists for the past decade: why are rates of colon, breast, kidney, uterine, and other cancers rising sharply among adults under 50, while those same cancers continue to decline in older adults who have had decades more time to accumulate cellular damage?
The answer, researchers suggest, may not be that something uniquely bad happened to one generation — but that modern life has accelerated the pace at which bodies accumulate biological wear across successive generations of young adults.
Why This Matters
Cancer has historically been understood as a disease of aging. Cells accumulate genetic damage throughout life, and the longer a person lives, the more opportunities exist for that damage to trigger tumor formation. The typical American's cancer risk rises steeply after 50.
But that framework has been challenged by a decade of data showing that certain cancers are rising fastest in the least expected age group: adults in their 30s and 40s. Early-onset colorectal cancer — diagnosed before age 50 — has risen so sharply in younger adults that major medical organizations, including the American Cancer Society, moved the recommended screening age from 50 to 45. Breast, kidney, and uterine cancers show similar trends in younger cohorts. By 2023, early-onset cancer diagnoses had risen approximately 25% globally between 1990 and 2019, according to prior analyses.
Researchers have struggled to identify a single cause. The Washington University study's contribution is offering a unifying biological measure — biological age — that captures the cumulative effect of many modern lifestyle and environmental exposures simultaneously, rather than requiring researchers to isolate any single factor.
What We Know So Far
The study, led by Dr. Yin Cao, a molecular epidemiologist at Washington University's Division of Public Health Sciences and a researcher at the Alvin J. Siteman Cancer Center, analyzed data from more than 164,000 people across two large population-based cohorts: one in the United States and one in the United Kingdom.
Rather than using chronological age, researchers measured biological age through blood-based biomarkers — markers of inflammation, metabolic function, kidney function, and immune health — using validated biological aging scoring systems. They then compared biological age to chronological age to calculate an "age gap" for each participant.
The key findings, according to WashU Medicine: participants born in more recent birth cohorts had larger age gaps — meaning their bodies appeared biologically older than their stated age more consistently than participants born in earlier decades. In the U.S. cohort, participants born in the 1990s had substantially higher biological age scores than those born in the 1960s at the same chronological age.
Each unit increase in biological aging was associated with an 8% higher risk of developing cancer before age 55. The researchers also identified organ-specific aging patterns linked to specific cancer risks: an immune system that appeared biologically older than its chronological age was associated with early-onset lung cancer; fat tissue that appeared older was associated with early-onset colorectal cancer.
"If we can identify younger people with the highest cancer risk when they are still healthy, we can focus on prevention and early-detection strategies for the individuals who will benefit most," said Dr. Cao, according to ScienceAlert reporting.
Where the Concern Is Highest
The study found the pattern of faster biological aging in both the U.S. and U.K. cohorts, suggesting the trend is not limited to a specific geographic or healthcare context but reflects broader shared exposures across modern high-income societies.
Within the U.S., early-onset cancer rates are rising in all major population centers — but the trend is particularly significant in communities where ultra-processed food is the dominant food environment, obesity rates are high, sleep disruption is prevalent, and environmental chemical exposures are elevated.
Demographic analysis in prior early-onset cancer research has highlighted Black Americans as facing both higher rates of early-onset colorectal cancer and greater barriers to early screening and intervention — a disparity that, if biological aging is a meaningful risk predictor, would make early biological age assessment tools particularly important for this population.
What Researchers Say
"The trend of rising early-onset cancer is real, and it's happening faster than we previously recognized," Dr. Cao noted in the study's commentary. "Biological aging appears to be accumulating faster in younger people, and that faster accumulation is the bridge between modern exposures and cancer risk."
Dr. Cao and her colleagues did not identify a single cause of faster biological aging in younger generations. The study design documents the association between biological age and cancer risk across generations but does not isolate which specific exposures — ultra-processed food, sedentary behavior, obesity, sleep disruption, antibiotic exposure, environmental chemicals — are driving the generational shift. Prior research and the authors' discussion point to all of these as plausible contributors, individually and in combination.
An editorial accompanying the study in Nature Medicine noted that the findings provide "a compelling integrative framework" for early-onset cancer research, but cautioned that biological age scoring has not yet been validated as a clinical screening tool for cancer risk in individual patients.
What the Evidence Shows — and What It Does Not
This is a large observational study, not a clinical trial. It establishes that younger generations have higher biological age scores on average than older generations did at the same age, and that those higher scores are associated with increased cancer risk. It does not prove that any specific lifestyle or environmental factor is causing both the faster aging and the cancer risk — the mechanism is inferred, not directly demonstrated.
Biological age scoring tools based on blood biomarkers have been validated in research settings but are not currently part of routine clinical care. A person cannot go to their doctor today and request a "biological age test" that is part of standard-of-care risk assessment for cancer.
MedicalDaily Evidence Check
- Study type: Large observational cohort study
- Published: June 22, 2026, Nature Medicine (DOI: 10.1038/s41591-026-04448-w)
- Institution: Washington University School of Medicine in St. Louis; Siteman Cancer Center
- Participants: 164,000+ across U.S. and U.K. cohorts
- What it found: Recent birth cohorts show faster biological aging than older cohorts at the same chronological age; each unit increase in biological aging is associated with 8% higher risk of cancer before age 55
- Cancer types linked: Colorectal, lung, uterine, kidney cancers noted in organ-specific aging analyses; general early-onset cancer risk measured across types
- What it did not prove: The specific cause of accelerated biological aging; that any single lifestyle factor explains the generational shift; that biological age testing is clinically ready for individual cancer screening
- What readers should know: This research adds biological evidence to the early-onset cancer trend; reducing modifiable risk factors — ultra-processed food, sedentary behavior, poor sleep, obesity — is the most actionable current response
Who Faces the Greatest Risk?
Based on the study's findings and prior early-onset cancer literature, the people most likely to have the highest biological age gaps — and thus the highest cancer risk the study describes — include:
- Young adults with high consumption of ultra-processed foods
- People with sedentary lifestyles and low levels of physical activity
- Those with obesity, particularly visceral (abdominal) fat
- People with chronic sleep disruption or irregular sleep patterns
- Young adults with a family history of colorectal, breast, or other early-onset cancers
- Those with frequent antibiotic use in childhood
- People with high occupational or environmental chemical exposures
The presence of these risk factors does not guarantee an individual has accelerated biological aging, and their absence does not guarantee protection. Risk is probabilistic, not deterministic.
Symptoms and Warning Signs to Watch For
The early-onset cancers associated with the biological aging trend often present with symptoms that young adults are likely to attribute to less serious causes. The most important are:
Colorectal cancer: A persistent change in bowel habits (diarrhea or constipation lasting more than a few weeks), rectal bleeding or blood in stool, persistent abdominal discomfort, unexplained weight loss, fatigue.
Breast cancer: A new lump or thickening in the breast or underarm, change in breast size or shape, skin dimpling or puckering, nipple changes.
Kidney cancer: Blood in urine (often painless), persistent flank pain below the ribs, unexplained weight loss, fatigue.
Uterine cancer: Abnormal vaginal bleeding — particularly any bleeding after menopause or unusual bleeding patterns before it.
Young adults who experience any of these symptoms should not assume they are too young to have cancer. A clinical evaluation is appropriate. Earlier diagnosis consistently improves outcomes.
What You Can Do Now
- Reduce ultra-processed food consumption. Choose whole foods, cook at home when possible, and reduce packaged snacks, processed meats, and sugar-sweetened beverages.
- Move more. The American Cancer Society recommends at least 150 to 300 minutes of moderate activity or 75 to 150 minutes of vigorous activity per week. Even incremental increases from sedentary baselines reduce cancer risk.
- Prioritize sleep. Chronic sleep disruption is associated with accelerated cellular aging. Aim for seven to nine hours per night and consistent sleep and wake times.
- Get screened at 45 for colorectal cancer — or earlier if you have a first-degree relative with colorectal cancer diagnosed before 60. The American Cancer Society recommends starting at 40 if you have that family history.
- Know your family cancer history. Early-onset cancers in a parent or sibling are a risk factor that warrants earlier or more frequent screening discussions with your doctor.
- Talk to your doctor about personal risk if you have several of the modifiable risk factors described. Some health systems are beginning to integrate biological aging assessment into precision health programs, though this is not yet standard care.
Cost and Access: What Patients Should Know
Colorectal cancer screening is covered at no cost by most insurance plans for people 45 and older under the ACA's preventive care provisions — meaning no cost-sharing even before the deductible is met. Colonoscopy and stool-based tests (FIT, Cologuard) are both covered. For people under 45 who have a family history or other risk factors, a physician can order a diagnostic colonoscopy, which is typically covered with cost-sharing.
Breast cancer screening is similarly covered for women 40 and older under most ACA-compliant plans.
For patients without insurance, the National Cancer Institute's cancer screening resources and the CDC's National Breast and Cervical Cancer Early Detection Program provide subsidized or free screening for eligible low-income individuals.
What Happens Next
The study authors' next steps include identifying which specific biological aging scores — and which biomarkers within those scores — are most predictive of particular early-onset cancer types. That level of specificity could eventually inform who should be screened earlier, with what test, and with what frequency. Research in this direction is underway as part of the Cancer Grand Challenges initiative funded by Cancer Research UK and the National Cancer Institute.
Whether biological age scoring tools will eventually move into clinical use as part of cancer risk assessment remains to be determined. For now, they are research instruments that illuminate a population-level trend — not a test your doctor can order today.
The Bottom Line
Washington University researchers found that millennials and Gen Z are biologically older than previous generations were at the same age — and that this accelerated biological aging is associated with a meaningfully higher risk of developing cancer before 55. The study does not identify a single cause, but points to the accumulated effects of modern diets, sedentary lifestyles, disrupted sleep, and environmental exposures beginning in childhood. The most actionable response is not to panic but to reduce modifiable risk factors now, start cancer screenings at the recommended ages, and see a clinician promptly for any symptoms that might suggest cancer regardless of how young you feel.
