Colon cancer is usually regarded as an old-age disease. Most new cases are diagnosed in over 50s. Despite declining rates in older adults, scientists have documented a worrying trend in the opposite direction in patients over the age of 20 years 30s.
Data from national cancer registries in Canada show that the rate of colon cancer increases in younger adults. The increase could even accelerate.
"We thought this trend would slow or flatten after people first saw it a few years ago," said Darren Brenner, epidemiologist for molecular cancer at the University of Calgary and lead author of The New Study Published Wednesday in the journal JAMA Network Open.
Between 2006 and 2015 was the last For the year for which figures are available, the incidence of colorectal cancer among Canadian men has fallen 50 years ago by 3.47 percent, as Dr. Brenner and his colleagues stated. And from 2010 to 2015, rates for women under the age of 50 rose 4.45 percent.
In Canada, colon and rectal cancers in older adults have steadily declined due to increased awareness of the disease and the widespread use of screening tests, such as colonoscopies that can identify and remove colon polyps before cancer develops.
[ Like the Science Times page on Facebook. | Sign up for the Science Times newsletter.
The pattern is similar to that observed by researchers in the United States. University of Texas researchers in Austin reported last week that the proportion of newly diagnosed colorectal patients under the age of 50 has risen from 10 percent in 2004 to 12.2 percent in 2015. Younger patients probably also had advanced cases more frequently ] than older patients.
Overall, the risk of colorectal cancer in younger adults is still significantly lower than in older adults. But the continued upward trend means Millennials are likely to be at increased risk as they age.
"They carry this risk so that they are at a much higher risk than their parents when they are 50 or 60 years old," said Rebecca Siegel, epidemiologist at the American Cancer Society.
Recent lifestyle changes can be partly to blame. For example, obesity and physical inactivity are associated with colon cancer, as are low-fiber diets. Patients with chronic inflammation or type 2 diabetes also have an increased risk of the disease.
However, experts are not entirely convinced that these are the only factors at work. According to Ms. Siegel, obesity trends in people with different ethnic and racial backgrounds do not always equate to an increase in colorectal cancer.
Some studies have found that obesity carries an increased risk of colorectal cancer, while others, including new JAMA research, have noted a greater increase in rectal cancers.
More research into what causes the increase In colorectal cancer, Ms Siegel encourages younger people to recognize signs early.
Persistent constipation, cramps, bloating, blood in the stool, unexplained weight loss, and fatigue can all be symptoms. Younger people and their doctors often overlook the warning signs because "cancer is not on their radar," said Frau Siegel.
The American Cancer Society now recommends that people of average risk over the age of 45 be screened for colorectal cancer. Researchers in Canada are also considering changes to the screening recommendations.
However, these revisions are unlikely to prevent cancer in patients who are even younger. "We need to understand why this trend is occurring in young people to prevent it," Dr. Burner.