If you’re overdue for a colonoscopy, let this be your reminder: Colorectal cancer rates are increasing for pretty much everyone.
While word has gotten out of rising colorectal cancer rates among younger adults, a new study found that rates are rising across all age groups up to the age of 69. Researchers from the University of Chicago found that the overall incidence rate for this type of cancer—the second leading cause of cancer-related deaths in the U.S.—rose for the first time in more than 20 years, according to a study published earlier this week in NEJM Evidence.
The age-adjusted incidence rate of colorectal cancer rose from 36.7 per 100,000 people in 2022 to 38.3 in 2023, the study’s authors found. By comparison, the incidence rate in 2000 was 55.2. The incidence rate among people between the ages of 45 to 49 rose nearly 13% from 2019 to 2023, the sharpest increase among any age group, though that’s likely driven by more people in this cohort undergoing screening for the testing. In 2021, the U.S. Preventive Services Task Force lowered the recommended age of first screening to 45 from 50.
“That means that screening is doing as we intend it to do—it’s catching cancer earlier,” Caitlin Murphy, the lead author of the study and a professor of pediatrics and public health sciences at the University of Chicago, said in a statement.
But earlier screening doesn’t explain why the incidence rate is also rising among older adults between the ages of 65 and 69 as they’re about 80% up-to-date with screening and historically benefitted from this detection method. The results suggest that unknown risk factors may be offsetting the previous gains from screening—and the study’s authors say they still need to understand why that’s happening.
“In terms of understanding the root cause, I think our study shows that we can consider that whatever might be causing colorectal cancer in younger people is now also causing it to increase in older people as well,” Murphy said.
THEORIES FOR THE ROOT CAUSE
Finding that root cause of colorectal cancer remains the biggest mystery for researchers to unravel. Earlier this year, new evidence showed that colorectal cancer is now the leading cause of cancer-related deaths among men and women under the age of 50. Meanwhile, nearly 160,000 Americans will be diagnosed with colorectal cancer this year, including both colon cancer and rectal cancer, according to estimates from the American Cancer Institute.
Theories for what causes colorectal cancer are wide ranging. A recent study found that faster biological aging could be a factor that’s associated with an increased risk of several early-onset cancers, including colorectal cancer. The authors of this latest study plan to explore another possible culprit: environmental chemical exposures.
Working with a toxicologist from Emory University, the team from the University of Chicago will measure thousands of environmental exposures to see which ones warrant further research, then test those chemicals on organoids, which are specialized models that can grow colons in a dish.
