A risk factor is anything that increases a person's chance of getting a disease. Some risk factors can be changed, and others cannot. Risk factors for cancer can include a person's age, sex, and family medical history. Others are linked to cancer-causing factors in the environment. Still others are related to lifestyle choices such as tobacco and alcohol use, diet, and sun exposure.
Having a risk factor for cancer means that a person is more likely to develop the disease at some point in their lives. However, having one or more risk factors does not necessarily mean that a person will get cancer. Some people with one or more risk factors never develop the disease, while other people who do develop cancer have no apparent risk factors. Even when a person who has a risk factor is diagnosed with cancer, there is no way to prove that the risk factor actually caused the cancer.
Different kinds of cancer have different risk factors. Some of the major risk factors include the following:
Overall, environmental factors, defined broadly to include tobacco use, diet, and infectious diseases, as well as chemicals and radiation cause an estimated 75% of all cancer cases in the United States. Among these factors, tobacco use, unhealthy diet, and physical activity are more likely to affect personal cancer risk. Research shows that about one-third of all cancer deaths are related to dietary factors and lack of physical activity in adulthood.
Certain cancers are related to viral infections and could be prevented by behavior changes or vaccines. More than 1 million skin cancers expected to be diagnosed in 2003 could have been prevented by protection from the sun's rays.