• Cancer rates in Americans under 45 have surged over the past two decades, researchers found.
• Diagnoses are increasing most rapidly in teens and people in their early 20s.
• Factors such as genetics, alcohol use, diet, and physical activity may affect cancer risk.

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There's new evidence that colon-cancer rates have skyrocketed in people younger than 45.

A team of researchers led by Dr. Islam Mohamed, a physician at the University of Missouri-Kansas City, analyzed CDC data on colon-cancer cases in Americans aged 10 to 44 over two decades since 1999.

The team found that cases have more than tripled in teenagers and more than doubled for people in their early 20s.

While the biggest jump in cancer diagnoses was in younger people, the surge in cancer rates was significant across all age groups under 45:

• Late 20s to early 30s: The rate of Americans diagnosed with colon cancer in this age range increased about 70% from 1999 to 2020.
• Late 30s: For this age group, the rate increased 58% over the same time period.
• Early 40s: This group had the highest overall rate. Cancer cases increased by 45% for Americans in their early 40s between 1999 and 2020.

The researchers plan to present the study at Digestive Disease Week, a meeting for professionals in gastroenterology and related fields, in Washington, DC, later this month.

They say young people need to be better educated about the disease and how to prevent and treat it.

"Colorectal cancer is no longer considered just a disease of the elderly population," Mohamed said in a press release. "It's important that the public is aware of signs and symptoms of colorectal cancer."

Colon-cancer signs to look out for

Regular testing can be particularly important for colon cancer because its symptoms are harder to recognize until the disease reaches more advanced stages.

Mohamed said the most common early signs of colon cancer include abdominal pain, rectal bleeding, iron deficiency, and changes to bathroom habits like diarrhea or constipation.

Though the increase is striking, the overall number of colon-cancer diagnoses in young Americans is still low. In 2020, there were 1.3 cases per 100,000 teenagers and two cases per 100,000 people in their early 20s.

The CDC says colonoscopy screenings are only recommended for people 45 and older.

Strategies to prevent colon cancer

Data suggests that people who consume a lot of processed foods and added sugar have a higher risk of developing colon cancer. Cutting back on those foods could help people avoid the disease.

To reduce your chances of developing colon cancer, doctors recommend eating a high-fiber diet and avoiding tobacco and alcohol. Regular exercise has also been linked to a lower risk of multiple types of cancer.

However, colon-cancer risk can also be genetic. And there's ongoing research is investigating whether the gut microbiome, or bacteria in the digestive system, plays a role in colon cancer and if potential risk factors include food additives or some antibiotics that disrupt microbes in the gut.