A risk factor is anything that increases a person’s chance of developing cancer. Some risk factors can be controlled, such as smoking, and some cannot be controlled, such as age and family history. Although risk factors can influence the development of cancer, most do not directly cause cancer. Some people with several risk factors never develop cancer, while others with no known risk factors do. However, knowing your risk factors and communicating them to your doctor may help you make more informed lifestyle and health-care choices.

The following factors may raise a person’s risk of developing stomach cancer:

Age. Most cases of stomach cancer occur in people over age 55.
Gender. Men have twice the risk of developing stomach cancer as women.
Family history. People who have a first-degree relative (a parent, child, or sibling) who has had stomach cancer are at increased risk for stomach cancer.
Race. Black people are more likely than white people to develop stomach cancer.
Diet. Eating foods preserved by drying, smoking, salting, or pickling may increase the risk of stomach cancer. Eating fresh fruits and vegetables may help lower the risk.

Bacteria. A common bacterium called Helicobacter pylori, which causes stomach inflammation and ulcers, may increase the risk of stomach cancer. However, most people who are infected with this bacterium never develop stomach cancer.
Previous surgery or health conditions. People who have had stomach surgery or have pernicious anemia (severe decrease in red blood cells) or achlorhydria (absence of hydrochloric acid in the gastric juices, which help digest food) have an increased risk of stomach cancer.
Occupational exposure. Exposure to certain dusts and fumes may increase the risk of developing stomach cancer.
Tobacco and alcohol. Tobacco use and excessive alcohol consumption may increase the risk of developing stomach cancer.
Genetic mutations. Certain inherited genetic disorders, such as hereditary diffuse gastric cancer, hereditary non-polyposis colorectal cancer (HNPCC or Lynch syndrome) and familial adenomatous polyposis (FAP) may increase the risk of stomach cancer.
Obesity. Excess body weight increases a man’s risk of developing stomach cancer. It is not clear whether obesity increases a woman’s risk of stomach cancer.