Colorectal cancer is rising in younger Americans as deaths increase.

Incidence of colorectal cancer has been increasing in adults in their 20s to 40s for decades, with cases among 20–39-year-olds rising about 2% per year since the mid-1990s; a recent study reported colorectal cancer is now a leading cause of cancer deaths for Americans under 50.

Colorectal cancer rates among younger Americans have risen steadily over the past three decades, and deaths in this age group have also increased. Researchers and cancer specialists report that more adults in their 20s, 30s and 40s are being diagnosed than in previous generations. Experts say the reasons are not yet clear and that research into diet, the gut microbiome, obesity and other factors is underway. Screening recommendations were lowered in 2021 for average-risk adults from age 50 to 45. Key facts: - The American Cancer Society reports incidence in adults ages 20–39 has climbed by about 2% per year since the mid-1990s. - About one in five people currently diagnosed with colorectal cancer are under age 55, according to the report. - A recent study published in JAMA found that colorectal cancer has become a leading cause of cancer deaths among Americans under 50, with increases in mortality since 2005. - Clinicians report two-thirds of younger patients are diagnosed at stage 3 or 4, and experts note multiple factors — including diet, the microbiome, obesity, smoking, alcohol use, family history and inflammatory bowel disease — are being studied. Summary: The rise in cases and deaths means a larger share of younger adults are being affected, and clinicians are working to better understand the causes. Research programs and ongoing studies aim to clarify contributing factors, and screening guidelines were updated in 2021 to begin at age 45 for average-risk adults; Undetermined at this time.