Cancer rates are increasing among adults of different ages in England, but a new study has uncovered a particularly concerning pattern among younger people. Rates of bowel and ovarian cancer have risen among younger adults (under 50), while the same increases have not been observed in older age groups.
The findings, published in the open-access journal BMJ Oncology, also show that several other cancers are becoming more common at a faster pace among younger adults than among those aged 50 and older.
Although excess body weight appears to play an important role, researchers say obesity alone cannot account for the increases. The findings suggest that additional factors may be contributing to the growing burden of cancer in younger generations.
Similar increases in cancer among people under 50 have been reported outside England. However, scientists still do not fully understand whether changing lifestyle habits and other established risk factors can explain these trends.
Cancer Rates Rise Across Multiple Age Groups
To investigate, researchers examined cancer incidence records collected by England’s National Disease Registry Service between 2001 and 2019. They compared trends in more than 20 cancer types among men and women aged 20 to 49 and adults aged 50 or older.
The team also analyzed national health survey data to track changes in established cancer risk factors. These included smoking, alcohol consumption, diet (high red/processed meat, low fiber intake), excess body weight (BMI), and insufficient physical activity. The researchers assessed how these factors changed across age groups and sexes and estimated how much they contributed to cancer cases.
The results revealed widespread increases in cancer incidence. Among younger women, 16 of the 22 cancer types examined showed statistically significant increases. Among younger men, rates rose significantly for 11 of 21 cancers.
Of particular concern were 11 cancers associated with known behavioral risk factors that became significantly more common among adults under 50. These included cancers of the thyroid, liver, kidney, gallbladder, bowel, pancreas, mouth, breast, and ovary, along with multiple myeloma and cancer of the uterine lining (endometrial).
Most of these cancers also increased significantly among adults over 50. However, bowel and ovarian cancers stood out because their incidence rose significantly among younger adults but not among older people.
The researchers also identified several cancers whose incidence increased more rapidly in younger women. These included endometrial, kidney, pancreatic, multiple myeloma, and thyroid cancers. Among men, multiple myeloma was the only cancer found to be increasing significantly faster in the younger age group.
Obesity Is a Major Factor, but It Doesn’t Explain Everything
The researchers examined how established lifestyle risks might help explain the increases. Of the 11 cancers of particular interest, 10 were associated with obesity, with mouth cancer being the exception.
Six cancers (liver, bowel, mouth, pancreas, kidney, and ovary) were linked to smoking, while four (liver, bowel, mouth, and breast) were associated with alcohol consumption. Three (bowel, breast, and endometrial) were connected to physical inactivity, and one (bowel) was linked to dietary factors.
Yet the findings revealed an important contradiction. Apart from excess weight, most of these established risk factors either remained relatively stable or improved among younger adults over the previous one to two decades.
Red meat consumption, for example, showed some of the largest reported improvements, with reductions of around 7% in the survey trends examined. Among younger men, average daily consumption fell from 38 grams in 2008 to 17 grams in 2018. Among younger women, it dropped from 22 grams to 10 grams over the same period.
Younger women also consumed substantially less processed meat than younger men, averaging about 10 grams per day compared with approximately 20 grams.
Fiber intake remained a concern, with more than 90% of younger adults failing to consume enough fiber in 2018. Nevertheless, average intake was generally stable or improved slightly among both sexes between 2009 and 2019. Older adults showed broadly similar dietary trends.
These findings raise questions about why cancer incidence continued to increase even as several recognized lifestyle risks were moving in a more favorable direction.
How Much Cancer Is Linked to Known Risk Factors?
Despite these improvements, established behavioral risk factors were still associated with a substantial proportion of cancer cases.
For men in 2019, the researchers estimated that these factors accounted for 68% of mouth cancer cases among younger adults and 65% among older adults. The corresponding figures were 42% and 48% for liver cancer, 49% and 53% for bowel cancer, 29% and 33% for kidney cancer, and 36% and 34% for pancreatic cancer.
Among women, the estimated proportions attributable to these risks were 52% for younger adults and 45% for older adults for mouth cancer. For endometrial cancer, the figures were 35% and 42%, while liver cancer accounted for 44% and 46%.
The corresponding estimates were 38% and 42% for bowel cancer, 33% and 37% for kidney cancer, 31% and 28% for pancreatic cancer, and 19% and 24% for gallbladder cancer.
Excess body weight was associated with more of the cancer types examined than any other individual risk factor. In 2019, the estimated proportion of cases attributable to excess weight varied considerably, from 5% for ovarian cancer to 37% for endometrial cancer.
Even so, the researchers found that increases in obesity could not fully account for the broader cancer trends.
“These patterns suggest that while similar risk factors across ages are likely, some cancers may have age-specific exposures, susceptibilities, or differences in screening and detection practices,” write the researchers.
Scientists Search for Other Explanations
The study was observational, meaning it could identify associations and trends but could not determine whether particular risk factors directly caused the increases in cancer incidence.
The researchers also acknowledged several limitations. Reliable national data covering long periods were unavailable for some risk factors, and the analysis focused exclusively on England rather than the entire United Kingdom.
In addition, their calculations assumed a 10-year delay between exposure to a risk factor and the development of cancer.
“The observed increasing cancer incidence despite declining trends in several behavioral risk factors may reflect the net effect of multiple influences operating in different directions. Other contributing factors not evaluated here, for example, reproductive history, early-life or prenatal risk factors, and changes in cancer diagnosis and detection practices, may also play a role,” they explain.
The researchers emphasized that obesity remains important, but increases in cancer cases cannot be attributed to weight alone.
“Although overweight and obesity are linked to 10 of the 11 cancers evaluated and account for a substantial proportion of cancer cases, both BMI-attributable and BMI-non-attributable incidence rates have increased — though the latter more slowly — suggesting other contributors,” they add.
Other potential explanations have been proposed for the increase in cancers among younger adults. These include greater consumption of ultra-processed foods and sugary drinks, childhood obesity, physical inactivity/sedentary behavior, antibiotic exposure, and air pollution.
However, many of these possible contributors have not shown the increases that might be expected if they were solely responsible for rising cancer rates.
“While these factors are common in England, most have shown stable or declining trends in the last decade,” the researchers note.
One possibility that deserves closer examination is disruption of the gut microbiome, the community of microorganisms living in the digestive system. Changes in these microbial populations have been suggested as a potential influence on cancer risk, although further research is needed to establish their role.
Cancer Remains More Common in Older Adults
While the rise in cancer among younger people is concerning, the researchers cautioned against overlooking the much greater number of cases that still occur among older adults.
The findings highlight the need to investigate cancer risk throughout life, including the possibility that exposures during childhood or even before birth may influence disease decades later.
“Although increases in cancer in younger adults are concerning, the absolute burden remains far higher in older adults, underscoring the public health and clinical importance of studying risk factors across all ages,” they conclude.
