Bowel and Ovarian Cancers Are Dramatically Rising in Young Adults, Scientists Aren’t Sure Why

Cancer incidence is increasing, especially among younger adults, and current risk factors don't fully account for the trend. Scientists suggest other underlying causes may be contributing.

Cancer patterns in England are shifting in a way that is drawing growing attention from researchers. While cancer has long been more common in older adults, new data show that several types are becoming increasingly frequent in younger people, in some cases rising faster than in older age groups.

A study published in BMJ Oncology reports that cases of multiple cancers are climbing across all ages. However, bowel and ovarian cancers stand out because their increase is strangely limited to adults under 50.

Researchers say this trend is unlikely to have a single cause. Although excess body weight remains a major factor, it does not fully account for what is being observed. Similar patterns have also been reported in other countries, suggesting a broader shift that is not yet fully understood.

Study Approach and Data Analysis

To explore this issue, researchers examined cancer incidence data in England from the National Disease Registry Service covering 2001 to 2019. They compared trends by sex across two age groups, 20–49 year olds and those aged 50 and older, across more than 20 cancer types.

They also analyzed national health surveys to track established risk factors such as smoking, alcohol use, diet (including high red and processed meat consumption and low fiber intake), excess weight (BMI), and physical inactivity. This allowed them to measure changes over time and estimate how much each factor contributed to cancer risk.

The results showed significant increases in new cases for 16 of 22 cancers in younger women and 11 of 21 cancers in younger men during the study period.

Cancers Increasing Among Younger Adults

Among people under 50, 11 cancers linked to known behavioral risk factors rose significantly. These included thyroid, multiple myeloma, liver, kidney, gallbladder, bowel, pancreatic, womb lining (endometrial), mouth, breast, and ovarian cancers.

In older adults, rates for most of these cancers also increased, except for bowel and ovarian cancers.

Five cancers, endometrial, kidney, pancreatic, multiple myeloma, and thyroid, rose more quickly in younger women than in older women. Multiple myeloma also increased faster in younger men than in older men.

Links to Risk Factors

All 11 cancers were associated with obesity except for mouth cancer. Smoking was linked to six of them (liver, bowel, mouth, pancreas, kidney, and ovary), alcohol to four (liver, bowel, mouth, and breast), and physical inactivity to three (bowel, breast, and endometrial). Diet was linked only to bowel cancer.

Despite these links, trends for most of these risk factors, apart from excess weight, have remained stable or improved among younger adults over the past one to two decades. The largest change was a drop of about 7% in red meat consumption.

Among younger men, average daily red meat intake fell from 38 g (1.34 oz) in 2008 to 17 g (0.60 oz) in 2018. For younger women, it declined from 22 g (0.78 oz) to 10 g (0.35 oz). Processed meat consumption in younger women was about half that of younger men, at 10 g (0.35 oz) compared with around 20 g (0.71 oz).

More than 90% of younger adults were not getting enough fiber in 2018. However, intake stayed steady or improved slightly between 2009 and 2019 in both sexes, with similar patterns seen in older adults.

Contribution of Behavioral Factors

Behavioral risk factors accounted for a large share of cancer cases. In 2019, they were linked to 68%–65% of mouth cancers in younger and older men, 42%–48% of liver cancers, 49%–53% of bowel cancers, 29%–33% of kidney cancers, and 36%–34% of pancreatic cancers.

Among women, these factors contributed to 52%–45% of mouth cancers, 35%–42% of endometrial cancers, 44%–46% of liver cancers, 38%–42% of bowel cancers, 33%–37% of kidney cancers, 31%–28% of pancreatic cancers, and 19% to 24% of gallbladder cancers.

Excess weight was the most influential factor overall, contributing from 5% of ovarian cancer cases to 37% of endometrial cancers.

"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.

This study is observational, meaning it cannot prove cause and effect. The researchers also note gaps in long-term national data for some risk factors and that the analysis focused only on England rather than the entire UK.

The results also assume a 10 year delay between exposure to risk factors and the development of cancer.

Additional Possible Influences

"The observed increasing cancer incidence despite declining trends in several behavioural 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.

"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 possible contributors include ultra-processed foods, childhood obesity, sedentary behavior, antibiotic use, sugary drinks, and air pollution.

"While these factors are common in England, most have shown stable or declining trends in the last decade," although another suggested contributory factor—a disordered gut microbiome–merits further investigation, they point out.

The researchers also stress the importance of context. "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.

Reference: "Temporal trends in behavioural risk factors for cancers with rising incidence in younger adults: an analysis of population-based data in England" by Montserrat Garcia-Closas, Zoey Richards, Reuben Frost, Marc J Gunter and Amy Berrington de Gonzalez, 28 April 2026, BMJ Oncology.
DOI: 10.1136/bmjonc-2025-000966