Colorectal cancer has tripled among some young people, but experts still aren't sure why

From 1999 to 2000, case rates increased by 333% in those 15 to 19 years old, and by 185% in those 20 to 24 years old.
A doctor visits with a young adult patient.
Posted at 5:16 PM, May 13, 2024

A new study says colorectal cancer has become far more common among young people in the U.S., where it more than tripled among teenagers from 1999 to 2020.

In that time frame, the rate of colorectal cancer increased by 500% among those 10 to 14 years old, by 333% in those 15 to 19 years old and by 185% in those 20 to 24 years old.

A team at the University of Missouri-Kansas City published the new findings after analyzing data on colorectal cancer rates from the Centers for Disease Control and Prevention

“Colorectal cancer is no longer considered just a disease of the elderly population,” said lead researcher Islam Mohamed, MD. “It’s important that the public is aware of signs and symptoms of colorectal cancer.”

Risk factors that may contribute to increased rates include obesity, tobacco use, low fiber intake and high intake of fat, processed meats and sugary drinks. Sedentary lifestyle may also contribute.

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Despite the increase, the findings do not warrant a change in colonoscopy screening practices, the researchers say.

Over the time period surveyed, the actual detection rates per 100,000 individuals went from 0.1 to 0.6 for those 10 to 14 years old, from 0.3 to 1.3 for those 15 to 19 years old and from 0.7 to 2 for those 20 to 24 years old.

The data also showed colorectal cancer rates climbed in older cohorts over the same time. Rates rose by 71% among those 30 to 34 years old, by 58% among those 35 to 39 years old and by 37% among those 40 to 44 years old.

Experts can't say for sure what's causing increased rates, though some hypothesize that changes to the human gut microbiome may play a part, possibly due to exposure to increased chemicals or microplastic contamination.

The CDC recommends that those 45 or older should receive screening. Those who believe they may be at increased risk for colorectal cancer should discuss the need for screening with their doctor.