Unhealthy behaviors increase risk of cancer
DEAR DOCTOR: Colorectal cancer is rising among young people, as I recently read in a news report. I thought colorectal cancer required a lifespan of unhealthy behavior.
DEAR READER: When I went through medical school, my professors had the same notions about colon cancer. The prevailing belief was that colon cancer was predominantly a disease of those over 50. Yes, colorectal cancers did occasionally occur in younger people, but these cases were attributed to familial diseases, such as Lynch syndrome or familial adenomatous polyposis, or to a significant family history of colon cancer. Ulcerative colitis or extensive Crohn’s disease also could put younger people at risk of colon cancer.
However, data have been warning for several years now of a rise in colon cancers diagnosed prior to age 50. A 2015 study in JAMA Surgery looked at colorectal cancer data from nine states between 1975 and 2010. During that time, the overall rate of colon cancer decreased, but only because the rate of colon cancer after the age of 50 decreased. In that study, 92 percent of colorectal cancer cases occurred after age 50; 8 percent occurred before age 50; and only 1 percent occurred between the ages of 20 and 34. In that same
study, the 35-to-49 age group experienced little change in the colon cancer rate, but among those ages 20 to 34, the rate of colorectal cancer cases increased by 2 percent per year.
When the researchers looked specifically at localized (meaning they hadn’t spread) rectal cancers and sigmoid colon cancers in this younger age group, they found that the rate of these cancers had increased by 4 percent.
A 2017 study looked at similar data from the same nine states between the years 1974 and 2013 and had similar findings.
The increased rates of colorectal cancers in this younger age group coincide with increased rates of obesity among young Americans, with multiple studies confirming the correlation. Further, colorectal cancer has been linked to decreased consumption of fruits, vegetables and fiber and an increased consumption of processed meats, characteristics of a modern American diet reliant upon processed food.
Robert Ashley, M.D., is an internist and assistant professor of medicine at the University of California, Los Angeles.
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