What Are the Risk Factors for Chronic Lymphocytic Leukemia?

A risk factor is something that affects a person's chance of getting a disease like 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, doesn’t 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). These include:

  • Exposure to certain chemicals
  • Family history
  • Gender
  • Race/ethnicity

The risk of getting CLL does not seem to be affected by smoking, diet, or infections.

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 more than twice the risk for this cancer.


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


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.

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master's-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Last Medical Review: January 6, 2015 Last Revised: April 11, 2016

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