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 some risk factors can make it more likely for a person to develop cancer.

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 can develop cancer and have no risk factors.
• Some risk factors are very well known. But there is ongoing research to find out other risk factors for many types of cancer.

Some risk factors, such as family history, may not be in your control. But others may be things you can change. Knowing the risk factors can help you make choices that might lower your risk. For example, if an unhealthy diet is a risk factor, you may choose to eat healthy foods. If being at a higher weight is a risk factor, your doctor may check your weight or help you with a weight-loss program.

Risk factors for stomach cancer include:

• Older age. Most people with stomach cancer are in their 60s or older.
• Being biologically male. Stomach cancer is more common than for others.
• Being Hispanic, African American, Asian, or Pacific Islander. In the U.S., stomach cancer is more common in these people than in others.
• Blood type. People with the blood type A have a higher risk.
• Diet. People who eat a lot of smoked, salted, pickled, and cured foods are at higher risk. Diets low in fruits and vegetables may increase risk.
• Smoking. Smoking increases the risk for stomach cancer.
• Alcohol. Heavy alcohol use may increase your risk, especially for cancers near the esophagus in the upper part of the stomach.
• Being at a higher weight or having obesity. These may increase the risk for stomach cancer near the esophagus in the upper part of the stomach, especially in those who are biologically male.
• Helicobacter pylori (H. pylori) infection. H. pylori are bacteria that cause many cases of stomach inflammation and ulcers. Long-term infection with H. pylori is also a major risk factor for stomach cancer.
• Past stomach surgery. Having part of your stomach removed for reasons other than cancer increases the risk for stomach cancer. Problems with reflux after surgery may also add to the risk.
• Pernicious anemia. People with this condition can't absorb vitamin B12. This leads to low red blood cell levels (anemia) and other problems.
• Stomach polyps. A polyp (adenoma) is a type of growth that can occur in the stomach. Having these may raise your risk for stomach cancer.
• Long-term inflammation. People with chronic or long-term inflammation of the stomach lining (gastritis) are at higher risk for stomach cancer.
• Common variable immune deficiency (CVID). People with CVID have frequent infections. This is because their immune system doesn't work the way it should to fight germs. They also tend to have other problems. These include gastritis and pernicious anemia. This raises their risk for stomach cancer.
• Workplace exposure. People who work in the coal, metal, and rubber industries are at increased risk. This may be due to inhaling toxic dust and fumes.
• Having family members with certain conditions. Some of these include:
  • Stomach cancer in parents, brothers, sisters, or children.
  • Lynch syndrome (hereditary nonpolyposis colorectal cancer).
  • Familial adenomatous polyposis.
  • Breast cancer gene mutations BRCA1 and BRCA2.
  • Li-Fraumeni syndrome.
  • Peutz-Jeghers syndrome.

Talk with your doctor about your risk factors for stomach cancer and what you can do about them.