Risks factors and 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.
Stomach cancer is more common in men than in women. Men have more than double the risk.
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
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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 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 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.
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).
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 acid reflux over a long time may have an increased risk of stomach cancer.
Changes to the 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.
People who have a brother, sister or parent with stomach cancer may have a higher 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.
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 or 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.