A new study by the American Cancer Society has unveiled a worrying trend, revealing that Generation X and millennials are at a higher risk of developing various types of cancer compared to their predecessors. This finding aligns with a growing body of evidence that certain cancers, including those of the bowel, breast, and pancreas, are becoming more common in younger populations.
The study, which analyzed data from nearly 24 million cancer patients collected from US cancer registries over a 20-year period starting in 2000, provides the most definitive evidence yet for a changing landscape of cancer incidence. The research team categorized the data based on cancer type, sex, and birth cohort—the five-year period during which individuals were born. They also implemented a statistical adjustment to account for the natural increase in cancer risk with age.
By examining the rates of the 34 most frequent cancers (those with at least 200,000 cases over the two decades), the study paints a stark picture. Shockingly, 17 different cancers are becoming increasingly common in the younger cohorts analyzed. For instance, individuals born in 1990 were between two and three times more likely to develop cancers of the small intestine, thyroid, kidney, and pancreas than those born in 1955.
The study also unearthed a troubling trend: younger generations are being diagnosed with cancer at a younger age. Across all ages and cancer types, the most dramatic increases in cancer were observed in the pancreas and small intestine among those under 30. In some instances, such as bowel cancer, the increased incidence in younger generations has even reversed previous trends of decline seen in older generations, suggesting that past public health gains are now being eroded.
The study points to lifestyle and behavior changes as potential culprits for the rising cancer risk in younger generations. Poor diet and increasingly sedentary lifestyles are two likely contributing factors. Ten of the 17 identified cancers, including bowel and breast cancer, have been associated with obesity. The US, like many other countries, is experiencing an obesity epidemic, with rates escalating year after year. Growing evidence suggests that childhood or early adulthood obesity can heighten the risk of certain cancers.
A related factor likely to play a significant role is the surge in consumption of ultra-processed foods. These foods have been linked to an increased probability of developing cancer. Increased binge drinking, particularly among millennial women, was highlighted by the study’s authors as a cause for the elevated rates of liver and esophageal cancers observed in this specific cohort. Meanwhile, in men, they noted a U-shaped trend (rates declined after an initial peak, then began rising again) for Kaposi’s sarcoma and anal cancer—two cancers associated with HIV infection. After a period of declining rates, this trend reversed for cohorts born from the mid-1970s onward. This mirrors the recent resurgence in HIV infection rates in the US.
Infection with human papillomavirus (HPV)—a sexually transmitted virus known to cause cervical cancer—may also contribute to the rise in anal cancer rates. It is estimated that 90% of anal cancers are caused by HPV infection. Interestingly, in contrast to the trend seen for anal cancer in men, the study observed a sharp decrease in cervical cancer risk for women born in the 1990 birth cohort—the first to have been vaccinated against HPV. When HPV vaccines were initially rolled out, they were only provided to girls, meaning that young men in this generation will not have been protected.
While some of the changes observed in cancer rates can be attributed to generational shifts in lifestyles and behaviors with known links to cancer, they cannot account for all the changes observed, such as increases in leukemia. The authors acknowledge that further research is needed to comprehend the causes of these cancers. Without a complete understanding of why these cancers are becoming more common, it will be challenging to take appropriate measures to reverse these trends.
However, the picture is not entirely bleak. Some cancers are actually becoming less common in younger generations. The study showed a consistent decline in the risk of developing lung cancer across successive generations. People born in 1990 are five times less likely to develop the disease compared to those born in 1955. Similar progress is also beginning to be seen for melanoma, where individuals born in 1990 were at lower risk than every other cohort born in the preceding 50 years. These trends reflect the success of public health campaigns aimed at discouraging tobacco use and encouraging sun-safe behavior. They highlight the effectiveness of changing behavior and making healthier choices in reducing our cancer risk.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
