A risk factor is something that affects a person's chance of getting a disease such as cancer. For example, exposing skin to strong sunlight is a risk factor for skin cancer. Smoking is a risk factor for a number of cancers.

But risk factors don't tell us everything. Having a risk factor, or even several risk factors, does not mean that you will get the disease. And many 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 is 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).

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 some pesticides may be linked to an increased risk of CLL, but more research in this area is needed.

Family history

First-degree relatives (parents, siblings, or children) of CLL patients have a 2- to 4-fold increased risk for this cancer.

Gender

CLL is slightly more common in males than females, although the reasons for this are not known.

Race/ethnicity

CLL is more common in North America and Europe than in Asia. Most experts think this is related to genetic differences rather than environmental factors because people keep the same risk even when they move from one area to another.

There are no other proven risk factors for CLL. The risk of getting CLL does not seem to be affected by smoking, diet, exposure to radiation, or infections.

Last Medical Review: 07/27/2009
Last Revised: 07/27/2009