Factors that increase a person’s risk of developing stomach cancer include older age, being male, and an H. pylori infection. By knowing the risk factors, people can take steps to lower their chances of developing stomach cancer.

Stomach cancer, or gastric cancer, starts when cells in a part of the stomach grow out of control. A person may not have symptoms at first, but early symptoms may include indigestion, bloating after eating, and mild nausea.

This article describes the risk factors for developing stomach cancer and when a person should seek medical attention.

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While stomach cancer can occur at any age, it is more common in older people.

According to the American Cancer Society, most people diagnosed with stomach cancer are in their 60s, 70s, and 80s.

According to a 2020 report from Japan, stomach cancer was most prevalent after the age of 65.

A person’s sex plays a role in their stomach cancer risk, with males being twice as likely to develop this disease than females.

Experts do not yet understand the reason for this difference.

The number of people with stomach cancer in the United States has been dropping by 1.5% each year for the last decade, and it is no longer a leading cause of death. However, it is still the fifth most common cancer worldwide.

The regions with the most instances of stomach cancer include:

  • East Asia
  • Eastern Europe
  • South and Central America

In the U.S., some ethnic groups are more likely to develop stomach cancer than others. The disease occurs more often among people from the following groups:

  • African Americans
  • Hispanics
  • Asian/Pacific Islanders
  • American Indian/Alaska Natives

Helicobacter pylori (H. pylori) is a bacterial infection of the stomach lining and is a major risk factor for stomach cancer. The bacteria spreads through direct contact with body fluids, such as saliva, vomit, and stool.

While many people have no symptoms of the infection, others develop stomach ulcers or painful stomach inflammation. Treatment may involve several rounds of antibiotics.

Learn more about H. pylori and stomach cancer.

According to a 2020 study, having overweight or obesity increases a person’s risk of several cancers, including stomach cancer.

Having extra weight increases inflammation and causes metabolic and endocrine changes that can promote cancer progression.

Having an unbalanced diet is a risk factor for developing stomach cancer.

Experts recommend eating a diet high in vegetables, fruits, and whole grains and limiting preserved or smoked meats or foods high in salt, as these can increase the risk.

Read about the link between diet and cancer.

Alcohol and tobacco use are risk factors for developing stomach cancer.

According to older research from 2017, alcohol can increase inflammation, which may encourage cancer growth.

People who smoke are also at higher risk than nonsmokers for stomach cancer. Smoking can also decrease the effectiveness of treating an H. pylori infection.

These risk factors are modifiable, meaning a person can decrease their risk of stomach cancer over time by limiting their alcohol intake and stopping smoking if they smoke.

Read more about alcohol and cancer risk.

A previous stomach surgery, such as gastrectomy or other surgery that alters the stomach, may increase a person’s risk of stomach cancer.

This may be due to changes in stomach acid production, which increases the risk of an H. pylori infection.

Other health conditions that may increase a person’s risk for stomach cancer include:

A person’s genetic makeup may play a role in determining their risk level for stomach cancer.

A mutation in the cadherin 1 gene (CHD1) may increase a person’s risk of developing stomach cancer early at an average age of 38 years. Females with this gene mutation are also at higher risk for developing lobular breast cancer.

A person has a higher risk of stomach cancer if their parent, child, or sibling has experienced it.

Having family cancer syndrome — genetic changes passed from parents — can also increase a person’s risk. These may include:

  • familial adenomatous polyposis
  • gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS)
  • familial intestinal gastric cancer (FIGC)
  • hereditary diffuse gastric cancer (HDGC)
  • juvenile polyposis syndrome
  • Li-Fraumeni syndrome
  • Lynch syndrome
  • Peutz-Jeghers syndrome

Read more about stomach cancer and family history.

People who work in certain occupations may be at higher risk of developing stomach cancer.

Working in the rubber or coal industry or working in an area with exposure to high levels of radiation can put a person at higher risk for stomach cancer.

Research shows that people with type A, B, or AB blood may be at higher risk for developing stomach cancer than people with type O blood.

According to one 2023 meta-analysis, people with blood types A, B, or AB are at higher risk of stomach cancer. A 2021 study reported similar findings.

People at high risk of developing stomach cancer should be aware of the symptoms. If someone experiences the following symptoms, they should contact a doctor for evaluation:

Read about how to prevent stomach cancer.

Several nonmodifiable factors, such as family history, genetics, age, sex, and blood type, can put a person at increased risk of developing stomach cancer.

However, several risk factors for stomach cancer are modifiable. People can lower their risk by making lifestyle changes, such as limiting alcohol, not smoking, maintaining a moderate weight, and eating a balanced diet.

A person should contact a doctor if they experience persistent symptoms of stomach cancer, such as losing weight unexpectedly, having a decreased appetite, or blood in the stool.