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A risk factor is anything that raises your chances of getting a disease such as cancer. Different cancers have different risk factors. Some risk factors, like smoking, can be changed. Others, like a person’s age or family history, can’t be changed.

But having a risk factor, or even several risk factors, does not mean that you will get the disease. Many people with one or more risk factors never get cancer, while others who get cancer may have had few or no known risk factors.

Scientists have found several risk factors that make a person more likely to get stomach cancer. Some of these can be controlled, but others cannot.

Sex

Stomach cancer is more common in men than in women.

Age

Stomach cancer can occur in younger people, but the risk goes up as a person gets older. Most people diagnosed with stomach cancer are in their 60s, 70s, or 80s.

Ethnicity

In the United States, stomach cancer is more common in Hispanic Americans, African Americans, Native Americans, Asian Americans, and Pacific Islanders than it is in non-Hispanic White people.

Geography

Worldwide, stomach cancer is more common in East Asia, Eastern Europe, and South and Central America. This disease is less common in Africa and North America.

Helicobacter pylori infection

Infection with Helicobacter pylori (H pylori) bacteria seems to be a major cause of stomach cancer, especially cancers in the lower (distal) part of the stomach. Long-term infection of the stomach with this germ may lead to atrophic gastritis and other pre-cancerous changes of the inner lining of the stomach. 

People with stomach cancer have a higher rate of H pylori infection than people without this cancer. H pylori infection is also linked to some types of lymphoma of the stomach. Even so, most people who carry this germ in their stomach never develop cancer.

Being overweight or obese

Being overweight or obese is linked with an increased risk of cancers of the cardia (the upper part of the stomach near the esophagus).

Diet

Stomach cancer risk is increased in people whose diets include large amounts of foods preserved by salting, such as salted fish and meat and pickled vegetables.

Eating processed, grilled, or charcoaled meats regularly appears to increase risk of non-cardia stomach cancers.  

Eating few or no fruits likely increases the risk of stomach cancer.  On the other hand, eating lots of fresh fruits (especially citrus fruits) and raw vegetables appears to lower the risk of stomach cancer.  

Alcohol use

Alcohol use probably increases the risk of stomach cancer. The evidence for this link is strongest for people who have 3 or more drinks per day.

Tobacco use

Smoking increases stomach cancer risk, particularly for cancers of the upper part of the stomach near the esophagus. The rate of stomach cancer is about doubled in people who smoke.

Previous stomach surgery

Stomach cancers are more likely to develop in people who have had part of their stomach removed to treat non-cancerous diseases such as ulcers. This might be because the stomach makes less acid, which allows more harmful bacteria to be present. Reflux (backup) of bile from the small intestine into the stomach after surgery might also add to the increased risk. These cancers typically develop many years after the surgery.

Some types of stomach polyps

Polyps are non-cancerous growths on the lining of the stomach. Most types of polyps (such as hyperplastic polyps or inflammatory polyps) do not seem to increase a person’s risk of stomach cancer much, if at all. But adenomatous polyps – also called adenomas – can sometimes develop into cancer.

Pernicious anemia

Certain cells in the stomach lining normally make a substance called intrinsic factor (IF) that the body needs to absorb vitamin B12 from foods. People without enough IF may end up with a vitamin B12 deficiency, which affects the body’s ability to make new red blood cells and can cause other problems as well. This condition, called pernicious anemia, can be caused by certain autoimmune conditions, as well as by some types of stomach surgery. Along with anemia (having too few red blood cells), people with this disease have an increased risk of stomach cancer.

Menetrier disease (hypertrophic gastropathy)

In this condition, excess growth of the stomach's inner lining causes large folds in the lining and leads to low levels of stomach acid. Because this disease is very rare, it is not known exactly how much this increases the risk of stomach cancer.

Inherited cancer syndromes

Some people inherit gene mutations (changes) from their parents that lead to conditions that can raise their risk of stomach cancer. These inherited syndromes account for only a small percentage of stomach cancers worldwide.

Hereditary diffuse gastric cancer (HDGC)

This inherited syndrome greatly increases the risk of developing stomach cancer. This condition is rare, but the lifetime stomach cancer risk among affected people is up to 70%. Women with this syndrome also have an increased risk of invasive lobular breast cancer. This syndrome is most often caused by mutations in the CDH1 gene.

Lynch syndrome (hereditary non-polyposis colorectal cancer, or HNPCC)

Lynch syndrome (formerly known as HNPCC) is an inherited genetic disorder that increases the risk of colorectal cancer, stomach cancer, and some other cancers. This syndrome is caused by mutations in one of the mismatch repair (MMR) genes, such as MLH1 or MSH2. These genes normally help repair DNA that has been damaged.

Familial adenomatous polyposis (FAP)

People with FAP get many polyps in the colon, and sometimes in the stomach and intestines, starting at an early age. People with this syndrome have a very high risk of getting colorectal cancer and a slightly increased risk of getting stomach cancer. FAP is caused by mutations in the APC gene.

Gastric adenoma and proximal polyposis of the stomach (GAPPS)

This rare condition is caused by a mutation in a specific part of the APC gene. People with GAPPS develop many polyps in the stomach and have an increased risk of stomach cancer.

Li-Fraumeni syndrome

People with this syndrome have an increased risk of several types of cancer, including developing stomach cancer at a relatively young age. Li-Fraumeni syndrome is caused by a mutation in the TP53 gene.

Peutz-Jeghers syndrome (PJS)

People with this condition develop polyps in the stomach and intestines, as well as in other areas including the nose, the airways of the lungs, and the bladder. The polyps in the stomach and intestines are called hamartomas. They can cause problems like bleeding or blockage of the intestines. PJS can also cause dark freckle-like spots on the lips, inner cheeks and other areas. People with PJS have an increased risk of several types of cancer, including cancers of the colon, pancreas, stomach, and breast. This syndrome is caused by mutations in the STK11 gene.

A family history of stomach cancer

People with first-degree relatives (parents, siblings, or children) who have had stomach cancer are more likely to develop this disease, even without one of the inherited cancer syndromes described above. Still, most people who get stomach cancer do not have a family history of it.

Common variable immune deficiency (CVID)

In people with CVID, the immune system can’t make enough antibodies to help protect against germs. This can lead to frequent infections as well as other problems, including atrophic gastritis and pernicious anemia. People with CVID are more likely to get gastric lymphoma and stomach cancer.

Epstein-Barr virus (EBV) infection

Epstein-Barr virus causes infectious mononucleosis (also called mono). Most people are infected with this virus at some time in their lives, usually as children or teens.

EBV has been linked to nasopharyngeal cancer and to some forms of lymphoma. It is also found in the cancer cells of about 5% to 10% of people with stomach cancer, although it isn’t yet clear if the virus actually causes stomach cancer. Stomach cancers linked to EBV tend to be slower growing and have less of a tendency to spread.

Certain occupations

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

Having type A blood

Blood type groups refer to certain substances that are normally present on the surface of red blood cells and some other types of cells. These groups are important in matching blood for transfusions. For unknown reasons, people with type A blood have a higher risk of getting stomach cancer.