Five of the six cancers on the rise among both older and younger adults are linked to obesity. (Credit: Halfpoint on Shutterstock)
Colorectal cancer is the one exception, showing an elevated rate of increase among younger adults exclusively.
In A Nutshell
- Not just a young person problem: Five obesity-related cancers (thyroid, breast, kidney, endometrial, leukemia) are increasing at similar rates in both adults under 50 and those 50 and older across most of 42 countries studied
- Colorectal cancer is different: It’s the only cancer type rising significantly faster in younger adults than older adults, likely because screening prevents cases in older populations while younger people remain unscreened
- Obesity is a major culprit: All five cancers increasing across age groups have strong links to excess body weight, suggesting rising global obesity rates may be driving the trend in multiple generations
- The numbers tell the story: While younger adults face notable increases, older adults still account for 71% of cancer deaths worldwide—and their rates are climbing too
Cancer incidence is rising around the world, but an international study is challenging the popular narrative that young people are uniquely vulnerable to this trend.
Researchers analyzed cancer data from 42 countries across five continents and found that while several cancer types are indeed increasing in adults aged 20 to 49, most of these same cancers are also increasing in people 50 and older. The one exception was colorectal cancer, which showed a faster rate of increase in younger adults.
The findings, published in Annals of Internal Medicine, examined 15 years of data from 2003 to 2017 for 13 cancer types previously reported to be rising in younger populations. A separate editorial on the findings was subsequently published in the journal as well.
Six cancer types increased in younger adults in most countries during the study period: thyroid cancer, breast cancer, kidney cancer, endometrial cancer, leukemia, and colorectal cancer. Five of these six also increased in older adults in most countries. The exception was colorectal cancer, which increased in older adults in only about half the countries studied. What links most of them? Obesity.
Why Obesity Matters
Five of the six cancers that rose in both younger and older adults in most countries have known ties to obesity. Some connections are particularly strong. Endometrial cancer and kidney cancer rank among the cancer types most firmly linked to excess body weight, and both showed median annual increases above 1.6% in younger adults across the countries studied.
The researchers note that all the cancer types increasing in both age groups “were all related to obesity and included some of those most strongly related to obesity, such as endometrial and kidney cancer.”
Rising obesity rates represent a global phenomenon affecting multiple generations, which could help explain why these cancer types are climbing in both age groups. Preventable chronic conditions in midlife such as obesity and diabetes are established risk factors for cancer in older adults. Meanwhile, cumulative exposure to metabolic changes associated with obesity throughout life may set the stage for cancer at younger ages.
But the pattern breaks down with some cancers. Stomach cancer and esophageal cancer, which also have links to obesity, actually decreased in younger adults in more than half the countries examined. Obesity alone doesn’t tell the complete story.
A Challenge to Recent Headlines
For five of the six cancers increasing in younger adults, rates climbed at similar speeds in both younger and older adults. Between 2003 and 2017, thyroid cancer showed the largest median annual increase in younger adults at 3.57%, followed by kidney cancer at 2.21% and endometrial cancer at 1.66%.
Breast cancer rates rose by a median of 0.89% annually in younger adults, even though obesity is associated with lower breast cancer risk in premenopausal women. This exception adds another layer of complexity to understanding what’s driving cancer trends across different age groups.
The pattern challenges recent media attention and research focused primarily on early-onset cancer as a distinct phenomenon requiring specialized interventions.
The Colorectal Cancer Puzzle
Colorectal cancer stood out as the only type where the increase was distinctly sharper in younger adults. Rates rose in younger people in 88% of the countries studied but increased in older adults in only about half of those countries.
The difference might come down to screening. Colonoscopy and other screening methods not only catch cancer early but prevent it by removing precancerous polyps. This protective effect in screened populations could mask increases in older adults while leaving younger, unscreened adults exposed to rising risk factors.
Countries with established colorectal cancer screening programs showed the pattern most clearly. In the United States, where colonoscopy screening is widespread, incidence rates in older, screening-eligible adults have been falling for decades. Canada, Australia, New Zealand, Austria, Switzerland, and the United Kingdom showed similar splits between younger and older adults after implementing screening programs.
Some Cancers Are Declining
Several cancer types actually decreased in younger adults in more than half the countries examined. Stomach cancer rates fell in younger people in 77% of countries, with a median annual decrease of 1.62%. Esophageal cancer and oral cancer also declined in most countries studied.
In older adults, liver and oral cancer rates increased in more than half of countries, while stomach and esophageal cancer rates decreased. These varying patterns suggest different underlying causes and risk factor trends.
Prostate, gallbladder, and pancreatic cancer showed increases in younger adults in just over half the countries studied, with similar patterns in older adults.
Different Trends Across Continents
Most participating countries were high- or middle-income nations in Europe, Asia, North and South America, and Australasia. Uganda was the sole African nation represented.
Some trends varied by region. Prostate cancer increased in younger adults in 80% of European countries but only 40% of countries in the Americas. Thyroid and kidney cancer, however, increased in younger adults across most countries in Asia, Europe, and the Americas alike.
For thyroid cancer specifically, nine countries showed a recent decline in rates among younger adults even though the overall 15-year trend remained positive. This shift could reflect reduced screening and detection practices in some regions.
What This Means for Cancer Care
While younger adults with cancer face distinct challenges related to fertility, career disruption, and family planning, older adults still account for the vast majority of cancer cases and deaths worldwide. In 2020, people 50 and older comprised more than two-thirds of new cancer cases and 71% of cancer deaths globally.
The gap in case numbers is substantial. In the United States in 2022, roughly 50,000 breast cancer cases were diagnosed in women younger than 50 compared to 210,000 in those 50 and older. For prostate cancer: 4,000 cases in men younger than 50 versus 220,000 in older men. For colorectal cancer, the numbers were 21,000 in the younger group and 126,000 in the older group.
Despite large relative increases in rates for some cancers, most cancer types remain uncommon in younger adults. One U.S. analysis estimated about 5,000 additional breast cancer cases and 2,000 additional colorectal cancer cases were diagnosed in younger adults in 2019 compared to what would have been expected based on 2010 rates.
Understanding what drives the increases across age groups requires examining what researchers call the “global exposome,” the cumulative spectrum of environmental and behavioral exposures that shape disease risk. Obesity represents just one piece of this puzzle. Changes in diet, physical activity, antibiotic use, environmental pollutants, and microbiome composition all warrant investigation.
The projected financial toll is staggering. The cost of cancer care over the next 30 years is estimated to exceed $25 trillion globally, occurring alongside an anticipated shortage of oncology providers.
Missing from the Research
Both younger and older adults with cancer remain underrepresented in clinical trials. Younger adults comprised only 14% of participants in National Cancer Institute-sponsored trials for newly diagnosed cancer. Meanwhile, just 33% of participants in registration trials were 65 or older and only 10% were 75 or older. This gap means doctors have less evidence to guide treatment decisions for patients at both ends of the age spectrum.
Biological differences between cancers diagnosed at different ages also need more study. Early-onset colorectal cancer, for example, appears to have distinct molecular features compared to cancers diagnosed in older adults. Whether similar differences exist for other cancer types remains unclear.
The study has limitations. Data only extended through 2017, meaning the analysis doesn’t capture the most recent years. The countries included had high-quality cancer registries but weren’t nationally representative of all global regions, particularly low-income countries. Some countries relied on regional rather than national registries.
Rather than focusing exclusively on early-onset cancer as a unique crisis, the researchers argue their findings call for a broader examination of why cancer rates are climbing across all adult age groups in so many countries. The obesity connection provides one potential explanation, but unraveling the full picture will require research across multiple disciplines and age groups.
Disclaimer: This article is based on peer-reviewed research published in Annals of Internal Medicine. It is intended for informational purposes only and does not constitute medical advice. Readers should consult qualified healthcare professionals for personalized medical guidance. Cancer screening recommendations vary by age, family history, and individual risk factors.
Paper Summary
Methodology
Researchers used the International Agency for Research on Cancer’s GLOBOCAN database to analyze cancer incidence data from 42 countries in Asia, Europe, Africa, North and South America, and Australasia. The study included annual cancer incidence data from 2003 to 2017 for adults aged 20 years and older. Countries were eligible for inclusion only if they had high-quality population-based national or regional cancer registries with complete data for the 15-year study period. The researchers evaluated 13 cancer types previously reported to be increasing in younger adults: leukemia and colorectal, stomach, breast, prostate, endometrial, gallbladder, kidney, liver, esophageal, oral, pancreatic, and thyroid cancer. They used joinpoint regression to estimate the average annual percentage change in cancer incidence rates, allowing for trends to vary across time by fitting a piecewise linear function on log-transformed age-standardized rates. The study compared trends in younger adults (aged 20 to 49 years) with trends in older adults (aged 50 years or older) using statistical tests to determine whether differences between age groups were significant.
Results
Cancer incidence rates increased in younger adults in most countries (more than 75%) for six of the 13 cancer types studied between 2003 and 2017. These included thyroid cancer with a median average annual percentage change of 3.57%, breast cancer at 0.89%, colorectal cancer at 1.45%, kidney cancer at 2.21%, endometrial cancer at 1.66%, and leukemia at 0.78%. Incidence rates for these cancer types also increased in older adults in most countries, with median average annual percentage changes of 3% for thyroid cancer, 0.86% for breast cancer, 0.37% for colorectal cancer, 1.65% for kidney cancer, 1.20% for endometrial cancer, and 0.61% for leukemia. Colorectal cancer was the exception, increasing in older adults in only about half the countries studied, with the average annual percentage change greater in younger adults than older adults in 69% of countries. For liver, oral, esophageal, and stomach cancer, rates decreased in younger adults in more than half the countries. Prostate, gallbladder, and pancreatic cancer showed increases in younger adults in just over half the countries, with similar patterns in older adults. When accounting for multiple testing using Bayesian false-discovery probability, very few countries showed noteworthy differences in trends between younger and older adults except for colorectal cancer.
Limitations
Most countries with available data were high- or middle-income nations, limiting the generalizability of results to low-income countries and other global regions. The most recent data for the majority of countries were from 2017, meaning the study could not evaluate trends from the past five years. Some countries included in the analysis relied on regional cancer registries rather than national registries, which may not fully represent national trends. The study used average annual percentage change as a summary statistic, which may not capture complex trends identified through joinpoint regression in some cases. The researchers could not determine what specific factors or exposures were driving the observed increases in cancer incidence across age groups. Different approaches to cancer ascertainment and registry practices across countries, even among high-quality registries, could introduce variability in the data. The study did not examine trends in specific younger age subgroups such as adults aged 20 to 29 years. Screening and improved detection methods may have influenced incidence trends for some cancer types, making it difficult to separate true increases in cancer occurrence from increases in detection.
Funding and Disclosures
The study was funded by the Institute of Cancer Research and the National Institutes of Health Intramural Research Program. The funders had no role in the design, conduct, interpretation, or publication of the study. The authors completed disclosure forms, which are available with the published article.
Publication Information
Berrington de Gonzalez A, Brayley M, Frost R, Freedman N, Gunter MJ, Jackson I, Lapitan P, Shiels MS, García-Closas M. “Trends in Cancer Incidence in Younger and Older Adults: An International Comparative Analysis,” published October 21, 2025 in the Annals of Internal Medicine;178:000-000. doi:10.7326/ANNALS-24-02718. The corresponding author is Amy Berrington de Gonzalez at the Institute of Cancer Research, United Kingdom.