Study Finds Colorectal Cancer Rates Increasing Across Age Groups
Colorectal cancer incidence in the United States increased in 2023, reversing more than two decades of decline, according to research published in NEJM Evidence. The analysis found rising rates across nearly every age group younger than 70, extending a pattern previously associated primarily with younger adults.
Researchers led by University of Chicago epidemiologist Caitlin Murphy examined National Cancer Institute data from 2000 through 2023. The overall age-adjusted incidence rate fell from 55.2 cases per 100,000 people in 2000 to 36.7 in 2022, before increasing to 38.3 in 2023.
Adults ages 45 to 49 experienced the largest increase, with incidence rising 12.76% annually between 2019 and 2023. Researchers attributed much of that increase to screening guidelines lowering the starting age from 50 to 45, which enabled detection of cancers that might otherwise have remained undiagnosed.
However, screening changes do not explain the entire trend. Rates also increased among adults ages 65 to 69, while declines stalled among those ages 70 to 74. The upward pattern persisted after researchers excluded data from 2020 and 2021 to assess pandemic-related disruptions.
The researchers pointed to a possible birth cohort effect, in which people born during similar periods carry shared risks as they age. The underlying causes remain uncertain. Further research will examine environmental chemical exposures using blood samples and laboratory-grown colon tissue models to investigate potential associations and biological effects.
The report emphasizes screening as an important means of detecting colorectal cancer early. It notes that recommendations call for routine screening from ages 45 through 75 for adults at average risk. Options include colonoscopy and stool-based tests, with testing choices and frequency discussed with a clinician.
Researchers say continued national monitoring is needed to determine whether increases persist and to assess potential implications for cancer treatment and long-term care as affected generations grow older.