A growing body of research is drawing attention to an unsettling trend: several cancers are becoming more common among younger adults in England, even as many traditional lifestyle risk factors remain stable or improve. However, scientists say these known factors alone cannot fully account for the increase.
A major analysis conducted by researchers at the Institute of Cancer Research and Imperial College London examined cancer incidence between 2001 and 2019 among adults aged 20 to 49. The study identified 11 cancer types showing rising rates in this age group, including breast, colorectal (bowel), pancreatic, kidney, liver, gallbladder, thyroid, multiple myeloma, oral, endometrial, and ovarian cancers.
While these cancers are also increasing in older adults—where overall incidence remains far higher—researchers noted that the shared upward trend across age groups may suggest overlapping risk factors. However, they stressed that the underlying causes are likely to differ depending on cancer type and demographic group.
Two cancers in particular—colorectal and ovarian—stood out for showing increased incidence exclusively among younger adults. This pattern, researchers say, raises the possibility that unique or emerging risk factors may be influencing cancer development earlier in life.
The study also evaluated well-established risk factors such as smoking, alcohol consumption, diet, physical inactivity, and body weight. These are known to contribute significantly to cancer risk, with estimates ranging from about 7% to 65% of cases depending on cancer type. However, the researchers found that these behaviours have not worsened in younger populations in recent decades. In fact, smoking rates have declined, alcohol consumption has either decreased or remained stable, physical activity levels have improved in some groups, and intake of red and processed meats has generally fallen.
Obesity was the major exception to this pattern. It has steadily increased across adult age groups and is widely recognised as a contributor to multiple cancers, including those of the bowel, kidney, pancreas, liver, gallbladder, and uterus. Yet even here, researchers concluded that rising obesity levels alone do not fully explain the increase in cancer incidence among younger adults.
Even for cancers strongly associated with excess body weight, the observed rise in cases could not be entirely attributed to obesity trends, suggesting that additional factors are likely involved.
According to the researchers, the findings point to a gap in current understanding of cancer development in younger populations. They highlighted the need to investigate other possible drivers, including early-life exposures, environmental influences, biological changes, and improvements in diagnostic practices and screening that may be identifying more cases than in the past.
At the same time, they emphasised that known prevention strategies remain critical. Smoking and obesity continue to disproportionately affect more deprived communities, and rising obesity rates in these groups remain a significant public health concern.
Overall, the study underscores a growing scientific consensus: while lifestyle factors remain important, they do not fully explain the increasing cancer burden in younger adults, and broader investigation is urgently needed to identify what else may be contributing to the trend.