The risk for developing colon cancer increases with age. More than 90 percent of colorectal cancers occur in people who are 50 years old or older; however, incidence in those younger than 50 is increasing. Precancerous polyps and colorectal cancer may go undetected because many individuals experience no symptoms in the early stages.
On average, the lifetime risk of developing colon cancer is about one in 23 for men and women combined (4.5 percent), however, this varies widely according to individual risk factors. About 71 percent of cases arise in the colon and about 29 percent appear in the rectum.
The median age at diagnosis for colon cancer is 68 in men and 72 in women; for rectal cancer it is 63 years of age in both men and women. As a result of rising colon and rectal cancer incidence rates in younger age groups coincident with declining rates in older age groups, the proportion of cases diagnosed in individuals younger than age 50 increased from 6 percent in 1990 to 11 percent in 2013. Most of these cases (72 percent) occur in people who are in their 40s.
Colon cancer and rectal cancer incidence and mortality rates are highest in African Americans.
People with a parent, sibling or child who has been diagnosed with colorectal cancer are at a higher risk of developing the cancer than those without a family history. Many lifestyle-related factors have been linked to colon cancer including being overweight or obese, physical inactivity, diet, smoking and heavy alcohol use. These risk factors can be managed or changed in order to decrease the chance of developing colorectal polyps that can lead to cancer. Health experts recommend being more active and limiting the amount of red and processed meats in the diet while increasing the amount of fiber consumed.