Risk factors and causes

The exact cause of stomach cancer is still unclear.  But certain things called risk factors can increase the chances of developing it. These include:

  • Gender – Stomach cancer is more common in men.
  • Age – 95% of people who develop stomach cancer are over 50 years old.  
  • Helicobacter pylori (H. pylori) – This common stomach infection can increase the risk of developing stomach cancer if it’s present over a long period of time. 
  • Diet –Not enough fruit and vegetables, and a diet high in processed meats or smoked foods can increase risk.
  • Smoking 
  • Being overweight can increase the risk of certain stomach cancers
  • Stomach conditions – Long-term acid reflux or conditions which cause changes to the stomach lining may increase risk. If part of the stomach is removed during surgery for another condition (such as an ulcer), this can also increase risk.
  • Family history – If a family member has stomach cancer, you might have a slightly higher risk.
  • Genes – A very small number of families may have an inherited cancer gene that can increase risk.

Risk factors and possible causes of stomach cancer

The exact cause of stomach cancer isn’t known. But certain things called risk factors can increase the chance of developing stomach cancer. Having a risk factor doesn’t mean someone will get cancer. Just as not having a risk factor doesn’t mean that a person won’t get cancer.


Gender

Stomach cancer is more common in men than in women. Men have more than double the risk.


Age

The risk increases as we get older; 95 out of every 100 people (95%) who develop stomach cancer are over 50 years old.


Helicobacter pylori (H. pylori) infection

This is a common stomach infection that causes inflammation of the stomach lining. Over a long time, it can increase the risk of a cancer developing. People with stomach symptoms are now usually tested for H. pylori and get treated if they have it.


Diet

Diet can affect the risk of stomach cancer. A diet low in fresh fruit and vegetables or high in salt can increase risk. Eating a lot of processed meats and foods that are smoked or pickled can also increase risk.

The number of people in the UK who develop stomach cancer is decreasing, probably because refrigeration means we eat more fresh foods.


Smoking

Smoking increases the risk of stomach cancer. The longer a person smokes for and the more cigarettes they smoke, the greater the risk. The risk reduces when people stop smoking.


Being overweight

People who are very overweight have an increased risk of cancer in the area where the stomach joins with the gullet (oesophagus). This area is called the gastro-oesophageal junction (GOJ).


Stomach conditions

Acid reflux

Sometimes, acid from the stomach can flow back up into the gullet, causing indigestion and heartburn. Many people have this condition without it causing cancer. But, people with constant and more troublesome reflux over a long time may have an increased risk of stomach cancer.

Changes to stomach lining

Conditions such as atrophic gastritis and pernicious anaemia cause changes to the stomach lining and can increase risk.

Stomach surgery for another condition (such as an ulcer)

Removing part of the stomach reduces stomach acid. This means you have less protection from bacteria such as H pylori.


Family history

People who have a brother, sister or parent with stomach cancer may have a higher risk than average risk. This may be because close family members share some risk factors for stomach cancer such as eating a similar diet or having H. pylori infection. But, shared genes may also play a small part.


Genes

In a very small number of families, an inherited cancer gene increases the risk of stomach cancer. In families with an inherited cancer gene, there may be two or more people on the same side of the family with stomach cancer or related cancers (such as bowel and womb cancer). If someone has an inherited cancer gene, they are also more likely to develop stomach cancer at a younger age (under 50).

Stomach cancer is not infectious and can’t be passed from one person to another.