A risk factor is something that affects a person's chance of getting a disease like cancer. Different cancers have different risk factors. Some risk factors, like smoking, can be changed. Others, like a person’s age or family history, can’t be changed.

But risk factors don't tell us everything. Having a risk factor, or even many risk factors, doesn’t mean that you will get the disease. And some people who get the disease may not have had any known risk factors. Even if a person has a risk factor and develops cancer, it's often very hard to know how much that risk factor may have contributed to the cancer.

There are very few known risk factors for chronic lymphocytic leukemia (CLL). These include:
Age
Exposure to certain chemicals
Family history
Gender
Race/ethnicity
The risk of CLL does not seem to be linked to smoking, diet, or infections.

Age
The risk of CLL goes up as you get older. About 9 out of 10 people with CLL are over age 50.

Certain chemical exposures
Some studies have linked exposure to Agent Orange, an herbicide used during the Vietnam War, to an increased risk of CLL. Some other studies have suggested that farming and long-term exposure to certain pesticides may be linked to an increased risk of CLL, but more research is needed to be sure.

Radon exposure at home has been linked to an increased risk.

Family history
First-degree relatives (parents, siblings, or children) of people with CLL have more than twice the risk for this cancer.

Gender
CLL is slightly more common in males than females. The reasons for this are not known.

Race/ethnicity
CLL is more common in North America and Europe than in Asia. Asian people who live in the United States do not have a higher risk than those living in Asia. This is why experts think the differences in risk are related to genetics rather than environmental factors.