Why Are More Younger Adults Being Diagnosed With Colorectal Cancer?
Doctors and researchers are examining a notable shift in colorectal cancer: more adults under 50 are being diagnosed, including people without obvious risk factors such as obesity, heavy alcohol use, or family history. Andrew Chan, MD, a gastroenterologist and professor at Harvard Medical School, has observed this change over two decades in clinical practice.
According to the American Cancer Society’s 2026 report, overall colorectal cancer rates have declined since the mid-1980s. However, among people under 50, rates have risen by about 2.9 percent per year. Research also suggests that early-onset colorectal cancers may be more aggressive than cases diagnosed later in life.
The causes remain unclear. Scientists are investigating several possibilities, including diet, processed foods, microbiome changes, alcohol use, environmental chemicals, microplastics, sleep patterns, and other lifestyle or exposure-related factors. Chan is helping lead Team Prospect, a $25 million National Cancer Institute-funded project involving researchers from several countries and disciplines.
One emerging area of study is biological aging. Research led by cancer epidemiologist Yin Cao at Washington University found that people born after 1965 were more likely to show signs of accelerated biological aging than those born in the early 1950s. This accelerated aging was associated with higher risks of several cancers, including gastrointestinal cancers.
Scientists measure biological age using tools such as epigenetic clocks, which analyze chemical changes to DNA, or blood-based biomarkers. Researchers say these tools may eventually help identify people at higher risk for age-related diseases before symptoms appear.
At the same time, experts caution that reducing biological age through lifestyle changes may have limits. Studies are underway on drugs and compounds that target aging-related processes, including senescent cells, mitochondrial function, and vascular aging.
For now, physicians emphasize timely screening. Average-risk adults should begin colorectal cancer screening at age 45, while those with symptoms or family history should discuss earlier testing with a clinician.