A risk factor is anything that affects a person's chance ofgetting a disease such as cancer. Different cancers have different risk factors. Some risk factors, such as smoking, can be controlled. Others, like a person's age or family history, can't be changed. But risk factors don't tell us everything. Having a risk factor, or even several risk factors, does not mean that you will get the disease. And many people who get the disease may not have had any known risk factors.

Risk factors

Scientists have found some risk factors that make a person more likely to develop stomach cancer. Some of these can be controlled, others can't.

Bacteria infection: Infection with bacteria called Helicobacter pylori (H. pylori) seems to be a major cause of stomach cancer. Long-term infection with this germ may lead to inflammation and pre-cancerous changes to the inner layer of the stomach. This germ is also linked to some types of lymphoma of the stomach. But most people who carry this germ in their stomachs never get cancer.

Stomach lymphoma: People who have been treated for a certain type of stomach lymphoma have an increased risk of getting carcinoma of the stomach. This is probably because this stomach lymphoma is caused by infection with H. pylori.

Gender: Stomach cancer is more common in men than women.

Age: There is a sharp increase in stomach cancer after age 50. Most people are in their late 60s or older when this cancer is found.

Ethnicity: In the United States, stomach cancer is more common in Hispanic Americans and African Americans than in non-Hispanic whites. It is most common in Asian/Pacific Islanders.

Where a person lives: Stomach cancer is most common in Japan, China, Southern and Eastern Europe, and South and Central America. This disease is less common in Northern and Western Africa, South Central Asia, and North America.

Diet: An increased risk of stomach cancer is seen with diets high in smoked foods, salted fish and meats, and pickled vegetables. On the other hand, eating fresh fruits and vegetables that contain vitamins A and C seems to lower the risk of stomach cancer.

Tobacco use: Smoking about doubles the risk of stomach cancer for smokers.

Obesity: Being very overweight (obese) is a possible cause of stomach cancer, but the link is not yet clear.

Earlier stomach surgery: Stomach cancer is more likely to be found in people who have had part of their stomach removed to treat other problems like ulcers.

Pernicious anemia: In this disease, the stomach doesn't make enough of a protein that allows the body to absorb vitamin B12 from foods. This can lead to a shortage of red blood cells (anemia). Patients with this disease also have an increased risk of stomach cancer.

Menetrier disease: This rare disease involves changes in the stomach lining that might be linked to a risk of stomach cancer.

Type A blood: For unknown reasons, people with type A blood have a higher risk of getting stomach cancer.

Family history: People with close relatives who have had stomach cancer are more likely to get this disease. Also, some families have a gene change (mutation) that puts them at greater risk for getting colorectal cancer, as well as a slightly higher risk of stomach cancer.

Some types of stomach polyps: Polyps are small mushroom-like growths on the lining of the stomach. Most polyps do not increase the risk of stomach cancer. But one type (called adenomatous polyps or adenomas) sometimes change into stomach cancer.

Epstein-Barr virus: This virus causes "mono" (infectious mononucleosis). It has been found in the stomach cancers of some people.

Certain types of work: Workers in the coal, metal, and rubber industries seem to have a higher risk of getting stomach cancer.

While there are many risk factors for stomach cancer, we do not know exactly how these factors cause cells of the stomach to become cancer. Scientists are trying to learn how and why certain changes take place in the lining of the stomach and what part H. pylori plays in stomach cancer.

They are also looking at how gene changes (mutations) can cause normal stomach cells to change and form cancers. Most of the gene changes that are linked to stomach cancer take place after birth. Very few are inherited.

Last Medical Review: 11/30/2009
Last Revised: 11/30/2009