Risk Factors for Colorectal Cancer

Colorectal cancer risk factors are characteristics, medical conditions, inherited genetic changes, or lifestyle factors that can increase your chance of developing colorectal cancer. Some risk factors, such as age and family history, cannot be changed. Others, including smoking, diet, physical activity, and alcohol consumption, are considered modifiable risk factors.

Having one or more risk factors does not mean you will develop colorectal cancer, also called colon cancer or rectal cancer depending on where it begins. Some people develop the disease without known risk factors, while others who are considered high risk never develop cancer. Understanding your personal risk factors can help you and your healthcare provider determine when colorectal cancer screening should begin.

What are the main colorectal cancer risk factors?

There is usually no single reason why a person develops colorectal cancer. Instead, genetic, medical, environmental, and lifestyle factors may contribute to a person's overall cancer risk. Important colon cancer risk factors include age, colorectal polyps, inflammatory bowel disease, family history, inherited cancer syndromes, type 2 diabetes, smoking, alcohol use, excess body weight, physical inactivity, and certain dietary patterns.

Risk factors you can and cannot change

Colorectal cancer risk factors can generally be divided into factors you cannot change and potentially modifiable risk factors. Age, genetics, family history, and certain medical conditions cannot be changed, while smoking, alcohol consumption, diet, physical activity, and body weight may be influenced by lifestyle choices.

Age and colorectal cancer risk

The risk of colorectal cancer increases with age. Although colorectal cancer can occur at any age, it is more commonly diagnosed in older adults. Rates have also been increasing among younger adults, making it important to discuss persistent symptoms regardless of age.

Personal history of colorectal polyps or colon cancer

A personal history of certain colorectal polyps can increase the risk of colon cancer. This is particularly true for adenomatous polyps, or adenomas, which can develop into cancer over time. People who have previously had colorectal cancer also have an increased risk of developing another colorectal cancer.

Do all colorectal polyps increase cancer risk?

No. There are several types of colorectal polyps, and they do not all have the same likelihood of becoming cancerous. The number, size, and characteristics of previous polyps can help determine how often follow-up screening is needed. Removing precancerous polyps during a colonoscopy can prevent some colorectal cancers from developing.

Family history and inherited colorectal cancer risk factors

A family history of colorectal cancer can increase your risk, particularly when a parent, sibling, or child has had colorectal cancer or certain adenomatous polyps. Risk may be higher when a close relative was diagnosed at a younger age or multiple relatives have had colorectal cancer.

A personal or family history of colorectal cancer can affect when screening should begin. If your history suggests an inherited cancer syndrome, your healthcare provider may recommend genetic counseling or genetic testing.

Lynch syndrome and cancer risk

Lynch syndrome, previously called hereditary non-polyposis colorectal cancer (HNPCC), is the most common inherited colorectal cancer syndrome. People with Lynch syndrome have a higher risk of colorectal cancer and several other cancers, including endometrial, ovarian, stomach, small intestine, and urinary tract cancers.

Familial adenomatous polyposis and other hereditary conditions

Familial adenomatous polyposis (FAP) is an inherited condition that causes many colorectal polyps to develop, often beginning at a young age. Without appropriate medical management, colorectal cancer risk is very high. Other hereditary conditions include attenuated FAP and MUTYH-associated polyposis.

Inflammatory bowel disease and colon cancer risk

Inflammatory bowel disease, including Crohn's disease and ulcerative colitis, can increase colorectal cancer risk because long-term inflammation can cause changes in cells lining the colon. Risk can depend on how long a person has had inflammatory bowel disease and how much of the colon is affected.

People with inflammatory bowel disease may need to begin colon cancer screening earlier and undergo screening more frequently than people at average risk.

Medical conditions that may increase colorectal cancer risk

Certain medical conditions are associated with an increased risk of colorectal cancer. People with type 2 diabetes have a moderately higher risk of developing colorectal cancer, which may be related to factors such as insulin resistance, chronic inflammation, and risk factors shared by both conditions.

Diet and colorectal cancer risk

Diet may influence colorectal cancer risk. Eating larger amounts of red and processed meats has been associated with increased risk, while eating patterns that include fruits, vegetables, whole grains, and fiber-rich foods may support overall health.

Research has also explored whether nutrients such as calcium are related to colorectal cancer risk. Talk with your healthcare provider before using calcium supplements or other supplements specifically for cancer prevention.

Physical activity, body weight, and colon cancer risk

Regular physical activity is associated with a lower risk of colorectal cancer, while physical inactivity is associated with increased risk. Being overweight or having obesity is also associated with higher risk.

Maintaining a healthy weight and staying physically active are healthy lifestyle choices that can support overall health.

Smoking, tobacco use, and colorectal cancer risk

Long-term smoking is associated with an increased risk of colorectal cancer. Tobacco smoke contains cancer-causing chemicals that can damage DNA throughout the body. Avoiding tobacco use can reduce the risk of many different cancers and other chronic diseases.

Alcohol consumption and colorectal cancer risk

Higher alcohol consumption is associated with an increased risk of colorectal cancer, with risk generally increasing as alcohol intake increases. Reducing alcohol can be part of a healthy lifestyle and may help reduce the risk of colorectal cancer and other cancers.

Does race or ethnicity affect colorectal cancer risk?

In the United States, Black Americans experience higher colorectal cancer incidence and mortality rates than many other racial and ethnic groups. These differences can reflect multiple factors, including access to screening and high-quality care, socioeconomic factors, health conditions, and environmental exposures.

Your individual medical and family history is more useful for determining personal risk than race or ethnicity alone.

How do risk factors affect colorectal cancer screening?

Risk factors can affect when screening begins, which screening tests are appropriate, and how often you need them. The American Cancer Society recommends that adults at average risk begin regular colorectal cancer screening at age 45.

People at higher risk for colorectal cancer may need to start screening earlier or have it more often. This includes people with a personal history of colorectal cancer or certain polyps, a strong family history, inflammatory bowel disease, or an inherited cancer syndrome.

Who is considered at high risk for colorectal cancer?

Someone may be considered high risk because of a personal history of colorectal cancer or certain polyps, a strong family history, inflammatory bowel disease, or an inherited cancer syndrome. Being at high risk does not mean you will develop cancer, but your healthcare provider may recommend a different screening schedule.

Can you lower your risk of colorectal cancer?

You cannot change factors such as your age, genetics, or family history. However, addressing modifiable risk factors may help lower colorectal cancer risk. Healthy lifestyle choices include staying physically active, maintaining a healthy weight, avoiding tobacco, limiting alcohol, and eating a balanced diet.

Screening is also important because some tests can identify and remove precancerous polyps before they develop into cancer.

When should you talk to your doctor about your colorectal cancer risk?

Talk with your healthcare provider if you have a personal or family history of colorectal cancer or polyps, inflammatory bowel disease, or relatives with an inherited cancer syndrome. Knowing which relatives had cancer, what type they had, and their age at diagnosis can help determine whether earlier screening or genetic counseling may be appropriate.

Even without known risk factors, routine colorectal cancer screening remains important. People at average risk can still develop colorectal cancer, which is why screening is recommended even when you feel healthy and have no family history.