The exact cause of stomach cancer is unknown, though there are risk factors that can increase the likelihood of developing this type of cancer. Just because someone has a risk factor does not mean they will have cancer, and not having a risk factor does not mean they will not develop cancer.


Stomach cancer is more common in men than in women.

Age, y

The risk increases as people age, and most cases occur in people over the age of 50.

Helicobacter pylori (H. pylori) infection

This is a common stomach infection that causes the lining of the stomach to become inflamed. When this infection becomes prolonged, it can increase the risk of developing cancer.


Diet can affect the risk of developing stomach cancer. Diets that are low in fresh fruits and vegetables or high in sat may increase the risk. Eating large quantities of meat and processed or smoked foods may increase the risk.


Smoking increases the risk of stomach cancer. The longer you smoke and the more cigarettes you consume, the greater the risk. The risk goes down if you quit smoking.

Being overweight

People who are overweight have a higher risk of cancer in the area where the stomach joins the esophagus, called the gastroesophageal junction.

  • Stomach conditions
  • Acid reflux
    Stomach acid may sometimes flow back into the esophagus, causing indigestion and heartburn. Many people have this condition and never get cancer, though people with acid reflux over a long period of time can be at a higher risk of developing it.
  • Changes to the lining of the stomach
    Conditions such as atrophic gastritis and pernicious anemia can cause changes to the stomach lining and increase the risk of cancer.
  • Stomach surgery to treat another disease (such as an ulcer)
    Extracting part of the stomach lowers the level of acid, which means you may be more susceptible to bacterias like H. pylori.

Family history

People who have one parent or sibling with stomach cancer can be at a higher level of risk than the average. This may be because immediate family members share some risk factors such as diet. However, genes can also have their own role.


In a small number of families, a hereditary gene mutation exists which increases the risk of having stomach cancer. In such cases, two or more members of the family may have stomach cancer or other related cancers (such as cancer of the intestine or uterus). If there is an inherited cancer gene, it also increases the chances of developing cancer at a younger age (under age 50).

Stomach cancer is not contagious and cannot be transmitted from one person to another.