For the great majority of people, the major factor that increases a person’s risk for colorectal cancer (CRC) is increasing age. Risk increases dramatically after age 50 years; 90% of all CRCs are diagnosed after this age. Incidence and mortality rates are higher in African American individuals compared with other races; however, a meta-analysis found no evidence that African American individuals have higher rates of precancerous lesions.[1,2] The history of CRC in a first-degree relative, especially if before the age of 55 years, roughly doubles the risk. A personal history of CRC, high-risk adenomas, or ovarian cancer also increases the risk.[3] Other risk factors are weaker than age and family history. People with an inflammatory bowel disease, such as ulcerative colitis or Crohn disease, have a much higher risk of CRC starting about 8 years after disease onset and are recommended to have frequent colonoscopic surveillance.[4] A small percentage (<5%) of CRCs occur in people with a genetic predisposition, including familial adenomatous polyposis and hereditary nonpolyposis coli.

Based on solid evidence, screening for colorectal cancer (CRC) reduces CRC mortality. In addition, there is solid evidence that some CRC screening modalities also reduce CRC incidence. A meta-analysis of flexible sigmoidoscopy randomized controlled trials found that screening with sigmoidoscopy reduces all-cause mortality.

https://www.cancer.gov/types/colorectal/hp/colorectal-screening-pdq#_342_toc

 that adults age 45 to 75 be screened for colorectal cancer. The Task Force recommends that adults age 76 to 85 ask their doctor if they should be screened.
https://www.cdc.gov/cancer/colorectal/basic_info/screening/index.htm

If you think you are at increased risk for colorectal cancer, speak with your doctor about—