WASHINGTON, Jan. 9 (Xinhua) -- A cancer typically found in older adults has been killing younger people for reasons that has puzzled cancer epidemiologists in the past. But a new study may provide a clue, the U.S. digital news website Vox reported Tuesday.
The latest statistics from the American Cancer Society (ACS) reveal that adults under the age of 55 have seen their colorectal cancer rate rise 2 percent per year since the mid-1990s. Those born in 1990 have double the risk of developing colon cancer and four times the risk of getting rectal cancer compared to those born around 1950.
"It's not like the problem is bad and has stabilized," said Thomas Weber, a New York-based Northwell Health physician who specializes in surgical oncology, who organizes an annual summit for researchers trying to solve the mystery. "The problem has continued to worsen."
Researchers may have found one potential clue. Since 1980, the prevalence of obesity has doubled in more than 70 countries around the world. A recent study published by JAMA, a peer-reviewed medical journal, looked at over 85,000 women between the ages of 25 to 42 for about 22 years, and found a link between a higher body weight and a greater risk of colorectal cancer.
The scientists mapped early-onset colorectal cancers against body mass index (BMI) to figure out whether having a higher BMI at any point in a person's life was associated with the greatest colorectal cancer risk before age 50.
The result showed that the 114 women who developed colorectal cancer in the study tended to have a higher BMIs. People with obesity (a BMI of 30) had nearly double the risk of early-onset colorectal cancer compared with women in the normal BMI range (18.5 to 22.9). In other words, it looked like as obesity rates climb, so does colorectal cancer risk.
However, the impact of obesity on cancer risk is difficult to investigate from other behaviors or attributes people with obesity may have, particularly related to diet. Moreover, the study only looked at a subset of cases. "There were 114 cases under the age of 50 (in the study), and there are some 16,000 cases a year of colorectal cancer of people under the age of 50 in the U.S.," Weber said.