A risk factor is anything that may increase your chance of having a disease. Risk factors for a certain type of cancer might include smoking, diet, family history, or many other things. The exact cause of someone's cancer may not be known. But risk factors can make it more likely for a person to have cancer.

Here are some things you should know about risk factors for cancer:

• Risk factors can increase a person's risk, but they don't always cause the disease.
• Some people with one or more risk factors never develop cancer. Other people with cancer have no known risk factors.
• Some risk factors are very well known. But there's ongoing research about risk factors for many types of cancer.

Some risk factors, such as family history, may not be in your control. But others, like smoking or diet, may be things you can change. Knowing about cancer risk factors can help you make choices that might lower your risk. For instance, if an unhealthy diet is a risk factor, you may choose to eat healthy foods. If excess weight is a risk factor, your doctor may check your weight and help you lose weight.

Risk factors for bile duct cancer include:

• Age. Older people are more likely to have bile duct cancer than younger people. Most people are diagnosed with this cancer in their 60s or 70s.
• Weighing too much. Being overweight or obese increases your risk for bile duct cancer.
• Race and geography. Bile duct cancer is highest in Hispanic Americans in the U.S. Outside the U.S., bile duct cancer is much more common in Southeast Asia and China. This is mostly because of a parasitic infection of the bile ducts with tiny worms called liver flukes. This infection is common in these parts of the world, and it increases the risk for bile duct cancer.
• Certain bile duct or liver diseases. People who have long-lasting (chronic) inflammation of the bile ducts have an increased risk for bile duct cancer. This inflammation can be caused by a disease called primary sclerosing cholangitis. Another condition that can raise your risk for bile duct cancer is having congenital cysts in bile ducts either inside or outside your liver. Chronic ulcerative colitis, stones in the bile ducts, metabolic dysfunction-associated steatotic liver disease (MASLD), cirrhosis of the liver, or abnormal bile duct anatomy may also increase your risk.
• Having had X-rays with contrast injection before or during the 1950s. A substance called Thorotrast was used as a contrast agent in X-rays between the 1930s and 1950s. The substance can cause bile duct cancer. If you had X-rays with Thorotrast during that time, you could be at an increased risk for bile duct cancer. Thorotrast is no longer used.
• Diabetes. People with type 1 or type 2 diabetes have a higher risk of bile duct cancer.
• Hepatitis. Hepatitis B or C infection puts you at higher risk.
• Alcohol and tobacco use. Some studies have shown that people who use alcohol, tobacco, or both have a higher risk of bile duct cancer, as well as many other more common kinds of cancer.

Talk with your doctor about your risk factors for bile duct cancer and what you can do about them. Some ways you may reduce your risk include the following:

• Eat a healthy diet and get regular exercise.
• Get to or stay at a healthy weight.
• Reduce or cut out alcohol.
• Don't use any form of tobacco and stay away from other people's tobacco smoke.
• Get a hepatitis B vaccine.
• Take steps to prevent hepatitis C infection.