Well-known risk factors such as smoking, alcohol use, diet, and physical activity have not been increasing among younger adults in recent decades, except for obesity. But researchers say that alone cannot fully explain the rise of cancer among young adults.
Eleven cancers are becoming more common in young people in England, according to a major study, but the rise cannot be fully explained by changes in lifestyle.
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Researchers at the Institute of Cancer Research and Imperial College London analysed cancer incidence between 2001 and 2019 in adults aged between 20 and 49 and identified 11 cancers with increasing rates, including breast, colorectal, pancreatic, and kidney cancers.
For most of these cancers, rates also rose in older adults, where cancer remains far more common overall. Researchers said this may point to some shared risk factors across age groups, although the picture is likely to vary by cancer type.
But two cancers stood out: colorectal and ovarian cancer, which showed rising rates only in younger adults, suggesting that unique factors may be affecting this age group.
The 11 cancers identified as increasing in younger adults are:
- Breast cancer
- Colorectal (bowel) cancer
- Pancreatic cancer
- Kidney cancer
- Liver cancer
- Gallbladder cancer
- Thyroid cancer
- Multiple myeloma (a type of blood cancer)
- Oral cancer
- Endometrial cancer
- Ovarian cancer
Researchers looked at well-known risk factors such as smoking, alcohol use, diet, physical activity and body weight.
They estimated that these factors account for a substantial share of some cancers, ranging from about 7% to 65%, depending on the cancer type.
However, most of these risks have not been increasing among younger adults in recent decades. Fewer people are smoking, alcohol use has fallen or remained stable, physical inactivity has generally decreased, and consumption of red and processed meat has dropped.
Obesity was the main exception. It has risen steadily across adult age groups and remains an important contributor to cancer risk.
But the researchers found that obesity alone did not explain the overall rise in cancer among younger adults.
Even for cancers associated with higher body weight, such as bowel, kidney, pancreatic, liver, gallbladder, and womb cancers, the increase could not be fully accounted for by rising obesity.
The findings suggest that known lifestyle factors are a small piece of the puzzle. Researchers said there is an urgent need to investigate other possible causes, including emerging risk factors, early life exposures, and the impact of increased testing, improved detection and screening practices.
They also stress that prevention efforts must continue, and that public health action is needed to address inequalities. Smoking and obesity remain more common in more deprived communities, and obesity has risen more sharply in these groups.
