Americans born in 1990 have double the risk of colon cancer and quadruple the risk of rectal cancer than those born around 1950, a new study suggests.
The study found that colorectal cancer is on the rise among young and middle-aged adults in their early 50s. Rectal cancer is growing particularly fast among people younger than 55, with 30 percent of diagnoses in people under 55.
"Trends in young people are a bellwether for the future disease burden," said Rebecca Siegel, of the American Cancer Society and lead author of the study that appeared in the Journal of the National Cancer Institute.
"Our finding that colorectal cancer risk for millennials has escalated back to the level of those born in the late 1800s is very sobering. Educational campaigns are needed to alert clinicians and the general public about this increase to help reduce delays in diagnosis, which are so prevalent in young people, but also to encourage healthier eating and more active lifestyles to try to reverse this trend."
Researchers note that rates of colorectal cancer have been falling since the 1980s with an even steeper decline in the past decade, which has been caused by more screening.
But they wanted to find out why some studies have shown a rising rate among people under 50 for whom screening is generally not done. For their study, researchers looked at cases of colorectal cancer in people over 20 from 1974 to 2013. There were 490,305 cases.
The data showed the rates of colon cancer initially decreased after 1974, but then grew by one or two percent from the mid-1980s to 2013 among adults aged 20 to 39. For people aged 40 to 54, the rates increased between .5 percent and one percent from the mid 1990s to 2013.
For rectal cancer, the increases were greater, with rates rising about three percent per year from 1974 to 2013 in adults aged 20 to 29. For adults between 30 and 39, there was a similar rise from 1980 to 2013. For adults between 40 and 54, rates increased by two percent from the 1990s to 2013.
Rates for adults older than 55 has been declining for about 40 years, researchers said.
Researchers say the results could change the age at which screening for colorectal cancer starts and cite 10,400 cases diagnosed in people in their 40s plus 12,800 cases in people in their early 50s.
"These numbers are similar to the total number of cervical cancers diagnosed, for which we recommend screening for the 95 million women ages 21 to 65 years," Siegel said.