H. pylori infection

Chronic infection of the mucosal layer of the stomach with H. pylori is a major risk factor for stomach cancer. This bacterium spreads from person to person through direct contact with saliva, vomit, or stool. Although many people with chronic H. pylori infections do not have symptoms, some develop stomach ulcers or an inflammation of the stomach called atrophic gastritis. In some people, atrophic gastritis leads to increasingly severe changes in the stomach lining and eventually to stomach cancer or gastric MALT lymphoma (see What Is Stomach Cancer?). Treatment of H. pylori infections reduces the risk of these types of stomach cancer.

Other medical conditions

The risk of stomach cancer is increased in people who have 

• chronic atrophic gastritis (thinning of the stomach lining caused by long-term inflammation of the stomach) 
• atrophic gastritis with intestinal metaplasia (a condition in which the cells that line the stomach are replaced by cells that normally line the intestines) 
• Epstein-Barr virus infection
• pernicious anemia (an autoimmune condition in which the intestines can’t properly absorb vitamin B12, resulting in a low red blood cell count)
• obesity (excess body weight) 
• gastroesophageal reflux disease (a condition in which stomach acid repeatedly flows back into the esophagus)

Genetics and family history

The risk of stomach cancer is increased, sometimes to very high levels, in people who have 

• a first-degree relative (parent, sibling, or child) who has had stomach cancer
• a family cancer syndrome, such as

  • familial adenomatous polyposis
  • familial intestinal gastric cancer (FIGC), a type of stomach cancer that runs in families but does not have a known genetic cause
  • gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS) (To learn more, see GAPPS.)
  • hereditary diffuse gastric cancer (HDGC) (To learn more, see HDGC.) 
  • juvenile polyposis syndrome
  • Li-Fraumeni syndrome
  • Lynch syndrome (also called hereditary nonpolyposis colon cancer and HNPCC)
  • Peutz-Jeghers syndrome
• Type A blood (To learn more, see the MedlinePlus page on blood types.)

Diet

Eating a diet that is low in fruits and vegetables or that is high in salted, smoked, or poorly preserved foods may increase the risk of stomach cancer.

Tobacco use

People who smoke have a higher risk of stomach cancer than nonsmokers. Smoking also makes treatment for H. pylori infection less effective. Smokers who stop smoking lower their risk of having stomach cancer over time. Learn about different tools to help you quit smoking and how to use them.

Environmental and occupational exposures

The risk of stomach cancer is increased in people who 

• work in the rubber or coal industry
• have been exposed to very high levels of radiation 

Having one or more of these risk factors does not necessarily mean you will get stomach cancer. Many people with risk factors never develop stomach cancer, whereas others with no known risk factors do. Talk with your doctor if you think you might be at increased risk. 

Stomach cancer screening or preventive surgery may be available to people at very high risk of stomach cancer, such as those with certain genetic conditions or family histories. Learn about stomach cancer screening.