Cancer is rising in younger adults, and scientists can't fully explain why

Key points

• Cancer incidence rose significantly among younger adults in England for 16 of 22 cancer types in women and 11 of 21 in men between 2001 and 2019.
• Bowel and ovarian cancers increased among people under 50 but not in older age groups.
• Obesity is linked to 10 of 11 cancers of concern, but researchers say it cannot fully explain the rising rates.

A new study has found that cancer rates are rising among younger adults in England, with bowel and ovarian cancers increasing significantly in people under 50 but not in older age groups. The research, published in the open-access journal BMJ Oncology, also showed that several other cancers are becoming more common at a faster pace among younger adults than among those aged 50 and older.

Researchers examined cancer incidence records from England's National Disease Registry Service between 2001 and 2019, comparing trends in more than 20 cancer types among men and women aged 20 to 49 and adults aged 50 or older. They also analyzed national health survey data to track changes in established risk factors such as smoking, alcohol consumption, diet, excess body weight and physical activity.

What the study found

Among younger women, 16 of the 22 cancer types examined showed statistically significant increases, while among younger men, rates rose significantly for 11 of 21 cancers. Eleven cancers linked to known behavioral risk factors became significantly more common among adults under 50, including cancers of the thyroid, liver, kidney, gallbladder, bowel, pancreas, mouth, breast and ovary, along with multiple myeloma and endometrial cancer.

Most of these cancers also increased among adults over 50, but bowel and ovarian cancers stood out because their incidence rose significantly only among younger people. Several cancers increased more rapidly in younger women, including endometrial, kidney, pancreatic, multiple myeloma and thyroid cancers, while multiple myeloma was the only cancer rising faster in younger men.

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

— the researchers

Obesity and other risk factors

Of the 11 cancers of particular interest, 10 were associated with obesity, with mouth cancer the exception. Six were linked to smoking, four to alcohol consumption, three to physical inactivity and one to dietary factors. Yet apart from excess weight, most of these established risk factors either remained stable or improved among younger adults over the previous one to two decades.

Red meat consumption showed some of the largest improvements, with average daily intake among younger men falling from 38 grams in 2008 to 17 grams in 2018, and among younger women from 22 grams to 10 grams. Fiber intake remained a concern, with more than 90% of younger adults failing to consume enough in 2018, though average intake was generally stable or improved slightly.

What researchers said

The researchers wrote that the patterns suggest some cancers may have age-specific exposures, susceptibilities or differences in screening and detection practices. They noted that 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.

They emphasized that obesity remains important but cannot alone account for the increases, noting that both BMI-attributable and BMI-non-attributable incidence rates have risen. They also cautioned against overlooking the much greater number of cases still occurring among older adults.

Limitations and next steps

The study was observational, meaning it could identify associations and trends but not determine whether particular risk factors directly caused the increases. Researchers acknowledged that 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.

Other potential explanations proposed for the rise in younger-adult cancers include greater consumption of ultra-processed foods and sugary drinks, childhood obesity, sedentary behavior, antibiotic exposure and air pollution. However, the researchers noted that most of these factors have shown stable or declining trends in England in the last decade, and they suggested disruption of the gut microbiome deserves closer examination.