Colon and rectal cancers are rising among younger adults – and researchers are not sure what is causing the increase, according to a study released Thursday.
For individuals younger than 50 years, the incidence of colorectal cancer increased by about 2% each year from 2011 through 2016, researchers said in a report published by CA: A Cancer Journal for Clinicians.
The study found, however, there were rapid reported declines in incidence for those 65 years and older — down by about 3% annually during those same years. The decline continues a trend from the 2000s, the study said.
For those aged 50-64 years, researchers found, the rate rose by about 1% annually.
Experts said better monitoring was a key factor in the decline among older patients, but the increase among younger adults is a mystery.
"Incidence rates are declining in adults 65 and older largely because of the rapid uptake of CRC (colorectal cancer) screening," said Rebecca Siegel, one of the study's researchers and scientific director of surveillance research for the American Cancer Society, the Washington Times reported. "The reason for rising incidence in younger adults remains unknown.
"The obesity epidemic is probably contributing, but doesn't seem to be the sole cause. Diet has a large influence on colorectal cancer risk, and there is a lot of research going on looking at how different things we consume, including drugs like antibiotics, influence gut health, specifically their role in determining the microorganisms that make up our microbiome."
The study found the number of people younger than 50 years who died from colorectal cancer increased by 1.3% each year from 2008 and 2017, while death rates for individuals 50 to 64 years increased by half that rate — 0.6% — each year.
Meanwhile, death rates for those 65 years and older dropped by 3% annually during the same time frame.
Colorectal cancer is the fourth most common cause of cancer death in both men and women in the U.S., according to the Centers for Disease Control and Prevention, the Washington Times noted.
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