The exact cause of stomach cancer is not clear. However, several risk factors have been identified that raise the risk of developing this illness.

Cancer is caused by mutations in the cellular DNA that alter the cell’s regulatory mechanisms such as growth, division and programmed cell death (apoptosis). Cells that contain this altered genetic material may grow in an uncontrollable manner, and give rise to a tumor. Any factors that increase the likelihood of genetic mutation such as exposure to radiation or toxic substances, increase the risk for cancer.

Some of the risk factors for stomach cancer include:

• Age – Most stomach cancers arise in people aged 55 or older and the mean age-at-diagnosis is 70 years.
• Gender – This cancer is twice as common among males than females.
• Family history – People who have a first degree relative such as a sister or parent who has had stomach cancer, are at an increased risk of developing the cancer. A hereditary condition called familial adenomatous polyposis also raises the risk of stomach cancer.
• Smoking – Smokers are nearly twice as likely to develop stomach cancer as non-smokers. Although cigarette smoke is mostly inhaled, some is also swallowed and reaches the stomach, where harmful tobacco toxins can then damage cells in the stomach. The longer a person smokes for and the more they smoke, the greater the risk for stomach cancer.
• Helicobacter pylori infection – H. pylori is a bacteria that can cause stomach ulcers, recurring indigestion and gastritis in some people. Inflammation of the stomach lining or chronic atrophic gastritis has been associated with an increased risk for stomach cancer in some studies.
• Diet – A diet rich in salt, pickled foods and smoked meats increases the risk of stomach cancer.
• Other medical conditions – Pernicious anaemia and peptic stomach disease are examples of other conditions that can increase the risk of stomach cancer.