Why Colorectal Cancer is Rising in Young Adults: Q&A with an Emory Winship Colorectal Surgeon

Colorectal cancer is now the leading cause of cancer death in adults under 50 in the U.S., making early screenings even more important. Patrick Sullivan, MD, colorectal surgeon at Emory Winship Cancer Institute, explains what patients need to know about cancers of the colon and rectum, symptoms not to ignore, factors that likely play a role in early onset and why colonoscopies are key.

Early-onset colorectal cancer is defined as cancer diagnosed before age 50. Here's what we know:

• Rates in adults under 50 have been rising about 2% per year since the 1990s.
• In people under 40, rates are rising even faster — about 3–4% per year.
• Early-onset cases now account for about 15% of all colorectal cancers.
• Colorectal cancer is now the leading cause of cancer death in men under 50 and the second leading cause of cancer death in women under 50, after breast cancer.
• This is not just happening in the U.S. It’s a global trend, especially in high-income countries. At the same time, however, rates in older adults are declining, largely due to improved screening.

What raises or lowers risk in younger adults?

There is no single cause. But several factors that likely play a role are:

• Genetics - Your genes are the most important risk factor. About half of colorectal cancers have an inherited component. Some people are born with genetic changes that increase their risk. In those cases, lifestyle or environmental exposures may “push” the disease to develop earlier.
• Obesity - Obesity (body mass index of over 30) is one of the strongest risk factors for colorectal cancer. Nearly 40% of U.S. adults are considered obese. Excess body fat changes hormone levels and increases inflammation, and both are linked to cancer risk.
• Diet - The typical Western diet plays a major role. Red meat and processed meats (like bacon, hot dogs and deli meats) increase risk, as do other highly processed foods, which often contain preservatives, additives and stabilizers, as well as sugary drinks. Smoking and drinking alcohol also increase risk.
• Sedentary lifestyle - Regular exercise lowers risk. Spending long hours sitting, especially more than 14 hours per day, is linked to a higher risk.
• Metabolic disorders - Conditions like Type 2 diabetes, high blood pressure and metabolic syndrome are associated with increased risk.
• Environmental exposures - Researchers are investigating environmental factors, including microplastics, heavy metals, pesticides and herbicides, as well as early and frequent antibiotic use, which may alter the microbiome (gut bacteria).