Stomach cancer is a type of cancer that develops in the cells lining the stomach. It occurs when the cells that line the stomach mutate and grow at an uncontrollable rate. There are several known risk factors for stomach cancer. 

Many factors can contribute to stomach cancer, including several precancerous conditions and genetic mutations.

Precancerous Conditions 

Stomach cancer usually starts with precancerous changes in the stomach’s inner lining. Precancerous conditions are changes that occur in the body that may lead to cancer. Several precancerous changes can happen in the stomach lining and raise the risk of stomach cancer. 

Precancerous conditions connected to stomach cancer may include:

• Helicobacter pylori infection: H. pylori bacteria can cause a chronic (long-term) infection in the stomach lining. Although the infection doesn’t usually have symptoms, it may lead to inflammation and ulcers (sores), which can cause precancerous changes that lead to stomach cancer. 
• Atrophic gastritis: This is a thinning of the stomach lining caused by chronic H. pylori infection. An autoimmune condition that damages the stomach lining, like thyroid disease, can also cause atrophic gastritis. Over time, this may cause stomach cancer. 
• Intestinal metaplasia: This is a condition where the cells lining the stomach look like those that usually line the intestine. These cellular changes may lead to stomach cancer. 
• Pernicious anemia: This type of anemia (red blood cell shortage) causes a vitamin B12 deficiency and raises the risk of stomach cancer. 

Gene Mutations

Cancer occurs when normal cells mutate and grow uncontrollably. Genes are parts of DNA (the material that controls how cells function) that pass on traits from parents to children. When DNA changes or mutates, it affects how the cell grows and divides.

Stomach cancer develops when the DNA in the cells lining the stomach mutates. There are several risk factors for this, including:

• Chronic H. pylori infection
• A diet rich in preserved meats
• Tobacco use

Inherited gene mutations, which are mutations passed down through families, can also cause stomach cancer. This means that your risk of stomach cancer is higher if one of your parents had the cancer. Researchers believe that inherited gene changes cause less than 3% of stomach cancer cases. 

The risk of stomach cancer increases if you have a family history of the disease. Having a parent or sibling with this type of cancer means that you are more likely to be diagnosed with it. 

The risk of stomach cancer is higher if you have a close family member with any of the following diseases or conditions: 

• Familial adenomatous polyposis 
• Familial intestinal gastric cancer 
• Gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS)
• Hereditary diffuse gastric cancer (HDGC)
• Juvenile polyposis syndrome 
• Li-Fraumeni syndrome
• Lynch syndrome 
• Peutz-Jeghers syndrome 

Some people are more likely to develop stomach cancer than others. In addition to precancerous conditions and family history, the following factors affect your risk: 

• Age: Anyone can develop stomach cancer, but the risk increases with age. The average age at diagnosis is 68. 
• Sex: People assigned male at birth are more likely to be diagnosed with stomach cancer than people assigned female at birth. 
• Ethnicity: People who are Black, Hispanic, Asian or Pacific Islander, and American Indian or Alaska Native are at higher risk for stomach cancer.

There are several known risk factors for stomach cancer, some of which are reversible.

1. Infections

A chronic infection with H. pylori is a strong risk factor for stomach cancer. Epstein-Barr virus (EBV), a viral infection, can also raise the risk of multiple types of cancer, including stomach cancer and lymphoma. EBV causes mononucleosis (mono), an illness with flu-like symptoms that most people will experience at some point in their lives. 

About 5-10% of people with stomach cancer have EBV present in the cancer cells. However, researchers are not certain why EBV raises the risk of stomach cancer. 

2. History of Polyps 

Stomach polyps are growths on the inner lining of the stomach. Most polyps do not affect a person’s cancer risk. One type of polyp, called adenomas, is known to increase the chance of cancer. 

3. History of Stomach Surgery 

People who’ve had stomach surgery in the past have a higher risk of stomach cancer. This is because people who’ve had at least some part of their stomach removed may produce less stomach acid. Stomach acid helps reduce harmful bacteria in the stomach. Having less acid may increase the amount of harmful bacteria, raising the risk of infection and cancer. 

4. Obesity

Some people who have a body weight that is classified as overweight or obese can have an increased risk for several types of cancer, including stomach cancer. 

5. Diet

Consuming a diet rich in processed meats, like bacon or deli meats, may raise the risk of stomach cancer. Meat that’s been smoked, grilled, charcoaled, or preserved with salt may lead to gene mutations and precancerous changes in the stomach. Other foods preserved in salt, like certain types of fish and pickled foods, may also increase the risk. 

Eating a diet rich in fruits and vegetables is known to decrease the risk of stomach cancer. The vitamins and antioxidants (substances that help prevent cell damage) found in fruits and vegetables lower the risk of infection and gene mutations. 

6. Alcohol or Tobacco Use

People who regularly use alcohol or tobacco may be at an increased risk for stomach cancer.

People who drink three alcoholic drinks or more per day are more likely to develop stomach cancer than those who do not drink. 

The rate of stomach cancer is doubled in people who smoke regularly. Smoking cigarettes or cigars increases the chances of developing gene mutations that lead to cancer. Tobacco use also makes H. pylori treatment less effective. 

7. Environmental Exposures 

Being around certain chemicals and substances increases the risk of stomach cancer. People who work in rubber or coal industries may breathe in harmful chemicals that increase the risk of genetic mutations. People exposed to high levels of radiation are also more likely to develop stomach cancer. 

8. Blood Type

People with type A and AB blood are more likely to develop stomach cancer than people with other blood types. Researchers are not certain why this blood type is at higher risk.

Stomach cancer is a type of cancer that develops in the lining of the stomach. It occurs when the cells in the stomach lining mutate and grow and divide uncontrollably. A chronic infection with H. pylori may cause inflammation in the stomach and increase the risk of cancer. 

Known risk factors of stomach cancer include precancerous conditions, certain genetic disorders, a family history of stomach cancer, diet, smoking, a history of stomach surgery, and certain infections. If you’re concerned about your risk of developing stomach cancer, reach out to your doctor.