Causes of Colorectal CancerThose things are thought to influence the development of colon and rectum cancer. They're referred to as risk factors and are as follows:
Age Age is the number one risk factor for colorectal cancer. More than 90% of people diagnosed with the disease are 50 or older and the average age of diagnosis is 64. By the time the cancer is diagnosed, it has often been growing for several years, first as a non-cancerous polyp and later as cancer. Research indicates that by age 50, one if four people has polyps. Alcohol Colorectal cancer has been linked to heavy alcohol use (e.g., more than eight drinks a week). Increased risk seems to be mainly associated with distilled spirits like gin, vodka, and bourbon. Diabetes Diabetics are up to 40% more likely to develop cancer of the colon and rectum than are people who do not have diabetes. Diet Diets high in fat and cholesterol (especially from animal sources) have been linked to an increased risk of colorectal cancer. Low-fiber diets have also been associated with increased risk, but the research isn't as clear. Environment The risk of developing colon or rectum cancer varies throughout the world. Studies indicate that colorectal cancer rates are lowest in Kuwait, India, and Romania and highest in the U.S., Switzerland, and Canada. But, it's not clear how much environmental factors impact that risk as opposed to other factors, like culture and the ability to identify the disease. Ethnic Background Research has found genetic mutations leading to colorectal cancer in Jewish people of Ashkenazi descent. In fact, Ashkenazi Jews are two-to-three times more likely to develop colorectal cancer than are members of the general population. (Read more about Ashkenazi Jews and colon cancer.) In general, minority populations are at greater risk of dying from colon and rectum cancer because they receive preventive care less often. This includes racial minorities such as Native Americans, Hispanic, Vietnamese, and black people, as well as social minorities such as gays and lesbians. Screening is a crucial step in preventing this disease. Exercise A sedentary lifestyle increases the risk of developing cancer of the colon or rectum. Gender The role of gender in colorectal cancer development is unclear. In geographic regions where the disease is more frequently detected (such as the U.S.), more men than women are diagnosed. But, a review of colorectal cancer cases worldwide indicates that men and women are at equal risk. Genetics For members of the general population, the risk of developing colorectal cancer is between three and six percent. The impact of genetics on this risk is minimal. About 75% of colorectal cancer cases are sporadic; they occur in people who have no (or very little) family history of the disease. However, the other 25% of cases are attributed to two types of colorectal cancers: familial and hereditary. Familial colorectal cancer accounts for about 20% of cases and hereditary colorectal cancer accounts for the remaining five percent. Both are attributed to genetic mutations passed from one generation to the next. Presence of the mutated genes that cause familial colorectal cancer increases the risk of developing the disease. The risk is almost three times greater when two immediate family members have colon or rectum cancer. It's ten times greater when three immediate family members have colon or rectum cancer. People who carry genetic mutations linked to hereditary colorectal cancer are the most likely to develop the disease. Individuals who carry the mutation that causes familial adenomatous polyposis (FAP) have almost a 100% chance of developing colorectal cancer by age 45. Someone who carries mutations linked to hereditary non-polyposis colorectal cancer (HNPCC) can have up to an 80% risk of developing the disease. FAP and HNPCC are the most common types of hereditary colorectal cancer. Family Medical History The medical history of a person’s family (immediate and extended) may impact his or her chances of developing cancer of the colon or rectum. Individuals are at increased risk when they have relatives who: - Were diagnosed with colorectal cancer or polyps; - Developed colon or rectum cancer before age 60; - Have a history of breast or ovarian cancer; - Died from stomach or abdominal cancer, since colorectal cancer has been misdiagnosed as these in the past; or - Died from bone or liver cancer, since they may have resulted from undiagnosed colon or rectum cancer. History of Polyps Virtually all colorectal cancer develops from adenomatous polyps, generally referred to simply as polyps. Although polyps don't always become cancerous, individuals with a history of polyps develop colorectal cancer more often than those without polyps. An individual’s risk of developing colorectal cancer increases with the number and size of the polyps present. Polyps larger than two centimeters (about the diameter of a nickel) have up to a 40% chance of being cancerous. History of Cancer Research indicates that women who have had breast, uterine, or ovarian cancer are at increased risk for developing colorectal cancer. Inflammatory Bowel Disease Chronic inflammation of the bowel, often caused by conditions such as ulcerative colitis and Chron’s disease, increases the risk of developing colorectal cancer. (However, ulcerative colitis increases risk more than Chron’s disease.) In general, the longer a person has had bowel inflammation, the greater his or her chance of developing colorectal cancer. This is because inflamed areas of the colon can give rise to abnormally-developed cells, which in time, can give rise to cancer cells. Smoking Long-term cigarette smoking increases a person’s risk of developing colorectal cancer for two main reasons: inhaled or swallowed tobacco smoke transports carcinogens to the colon and tobacco use appears to increase polyp size. (In general, the bigger the polyp, the greater the chance it will become cancerous.) Studies indicate that 12% of fatal colorectal cancers may be attributable to smoking. Weight Obesity, defined as having a Body Mass Index (BMI) greater than 30, increases the risk of developing colorectal cancer. (Calculate your BMI.) Extra fat in the waist (i.e., an “apple” shape) increases the risk of colon and rectum cancer more than having extra fat in the thighs or hips (i.e., a “pear” shape).
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