Cancer Is Rising Among Adults Under 50, and Lifestyle Factors Can’t Fully Explain Why
Cancer is becoming more common among adults across all age groups in England, but a new study has identified a particularly concerning increase among people under 50. Researchers found that several types of cancer, including bowel and ovarian cancer, are increasing more rapidly in younger adults than in older populations.
The analysis, published in BMJ Oncology, suggests that the rise in early-onset cancers cannot be fully explained by established lifestyle risk factors. Although excess body weight appears to play an important role, researchers believe additional influences may be contributing to the growing cancer burden among younger generations.
Rising cancer in younger adults
Researchers analyzed cancer registry records from England's National Disease Registry Service covering the period from 2001 to 2019. They examined incidence trends for more than 20 types of cancer among adults aged 20 to 49 and compared them with trends among people aged 50 and older during the same period.
Among younger women, 16 of 22 cancer types showed statistically significant increases in incidence. Among younger men, rates rose significantly for 11 of 21 cancers, indicating a widespread and sustained increase in early-onset cancers affecting multiple organs.
Eleven cancers associated with established behavioral risk factors became substantially more common among adults under 50. These included cancers of the bowel, pancreas, liver, kidney, gallbladder, thyroid, mouth, breast and ovary, along with multiple myeloma and endometrial cancer.
Most of these cancers also became more common among older adults. However, bowel and ovarian cancers were notable because their incidence increased significantly only in the younger age group. This pattern raises questions about age-specific risk factors and potential differences in diagnostic or screening practices.
Obesity important but not sufficient
The researchers examined major lifestyle risk factors using data from national health surveys. Their analysis focused on smoking, alcohol consumption, dietary habits, excess body weight and physical inactivity. They also estimated the contribution of these factors to cancer cases across different age and sex groups.
Of the 11 cancers examined in greater detail, 10 were associated with obesity, with mouth cancer being the exception. Six were linked to smoking, four to alcohol consumption, three to physical inactivity and one, bowel cancer, to dietary patterns.
However, most lifestyle risk factors other than obesity had either improved or remained relatively stable among younger adults over the previous one to two decades. Smoking rates declined, alcohol consumption decreased modestly, and consumption of red and processed meat also fell.
Among younger men, average red meat consumption decreased from 38 grams per day in 2008 to 17 grams in 2018. Younger women showed a similar pattern, although their consumption was generally lower. Processed meat intake was also lower among women than men, suggesting improvements in certain dietary habits.
Fiber consumption, which is particularly relevant to bowel health, remained inadequate for most younger adults. In 2018, more than 90% failed to meet recommended intake levels. Nevertheless, average fiber consumption remained stable or improved slightly between 2009 and 2019 in both younger and older age groups.
These findings present a challenge for researchers. Cancer incidence continues to rise among younger adults even as several established behavioral risk factors have moved in a more favorable direction. This discrepancy suggests that other influences may be contributing alongside obesity.
How much is linked to behavior?
The researchers estimated the proportion of cancer cases attributable to combined behavioral risk factors in 2019, examining differences by age and sex. The results demonstrate that modifiable exposures remain important contributors to cancer risk despite improvements in some lifestyle habits.
Among men under 50, behavioral factors were associated with 68% of mouth cancers, 49% of bowel cancers and approximately one-third of kidney and pancreatic cancers. For liver cancer, these factors accounted for an estimated 42% of cases in the same age group.
Among younger women, behavioral risk factors were linked to 52% of mouth cancers and more than one-third of bowel, kidney and pancreatic cancers. Approximately 35% of endometrial cancer cases among women under 50 were attributed to these exposures.
Excess body weight emerged as the most widespread individual risk factor, associated with more cancer types than smoking or alcohol consumption. Depending on the cancer, approximately 5% to 37% of cases among women were linked to obesity, with the highest proportion observed in endometrial cancer.
Nevertheless, the researchers concluded that increasing obesity rates could not fully account for the rise in cancers among younger adults. Incidence increased for cancers associated with high body mass index (BMI) and those without a clear BMI association, although the increase was more pronounced among BMI-related cancers.
Searching for missing explanations
The study was observational, meaning it could identify trends and associations but could not establish direct cause-and-effect relationships. The analysis was also restricted to England and assumed a 10-year interval between exposure to a risk factor and the development of cancer.
Reliable long-term information was unavailable for several potential contributors, including certain environmental exposures and detailed early-life factors. The authors caution that the observed trends are likely influenced by multiple interacting factors operating over several decades.
Possible explanations include reproductive history, prenatal and early-childhood exposures, and changes in cancer diagnosis or screening. Improvements in diagnostic sensitivity and greater awareness of symptoms may also contribute to cancers being identified earlier in life.
Other proposed factors include increased consumption of ultra-processed foods and sugary drinks, childhood obesity, sedentary behavior, widespread antibiotic use and air pollution. However, several of these trends have stabilized or improved in recent years, making it difficult to establish how much they contribute to rising early-onset cancer rates.
Changes in the gut microbiome have also attracted attention as a possible contributor, particularly in bowel cancer and other digestive system cancers. Alterations in intestinal bacteria, influenced by diet, medication and environmental exposures, may affect inflammation and immune responses in ways that could influence cancer risk.
Balancing concern with perspective
Although increasing cancer incidence among younger adults is concerning, researchers emphasize that cancer remains substantially more common in people over 50. The absolute number of cases among older adults is still many times higher than among those under 50.
Public health strategies must therefore address cancer prevention and treatment across the entire lifespan rather than concentrating exclusively on early-onset disease. This includes preventive measures, timely diagnosis and equitable access to effective treatment for younger and older patients alike.
The findings also point to the importance of investigating exposures that begin during childhood or even before birth. Maternal health, early nutrition, environmental pollutants and antibiotic exposure during childhood may all warrant further investigation as potential influences on long-term cancer risk.
Researchers stress that these unanswered questions should not overshadow established prevention recommendations. Avoiding tobacco, maintaining a healthy body weight, limiting alcohol consumption and remaining physically active can still help prevent a substantial proportion of cancers, even if these measures do not fully explain the rising incidence among younger adults.
At the same time, the study highlights the need for more detailed research into emerging risk factors and the biological mechanisms underlying early-onset cancer. Understanding why incidence is increasing in younger generations could help improve screening recommendations and support more targeted prevention strategies in the future.
