It’s also unexplained why colorectal cancer rates have been increasing in people under 50 while declining in older people. Researchers prospectively tracked the health of more than 85,000 women for 22 years, beginning when they were 25 to 42 years old. Compared with women of normal weight, a body mass index between 18.5 and 22.9 , obese women, with a B.M.I. over 30, had a 93 percent increased risk for the disease. “We have good screening and early detection for breast cancer in young women, but not for colorectal cancer,” said the senior author, Yin Cao, an assistant professor at Washington University Medical School.
He formulated a conclusion: “Our findings really highlight the importance of maintaining a healthy weight, beginning in early adulthood for the prevention of early-onset colorectal cancer.” The researchers emphasized that more studies are needed to uncover the best ways to identify young people at high risk of colorectal cancer at younger ages. In the United States, overall rates of new colorectal cancer cases and deaths from the disease have decreased steadily since 1980, largely owing to recommended colonoscopy screening starting at age 50. The new guidelines recommend screening begin at age 45.