Leukemia--Chronic Lymphocytic Overview

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Causes, Risk Factors, and Prevention TOPICS

What are the risk factors for chronic lymphocytic leukemia?

The exact cause of most cases of chronic lymphocytic leukemia (CLL) is not known. But in recent years a great deal has been learned about how normal lymphocytes and CLL cells differ. Normal human cells grow based mainly on the information contained in each cell's DNA. DNA is the chemical that carries our genes − the instructions for how our cells function. Each time a cell prepares to divide into 2 new cells, it must make a new copy of the DNA. This process is not perfect, and mistakes can happen that may affect genes within the DNA.

Sometimes people inherit DNA changes (mutations) from a parent that greatly increase their risk of getting certain types of cancer. But inherited changes rarely cause CLL. DNA changes linked to CLL usually occur during the person's lifetime, rather than having been inherited before birth.

Risk factors for chronic lymphocytic leukemia

A risk factor is something that affects a person's chance of getting a disease. Some risk factors, like smoking, can be controlled. Others, such as a person's age, can't be changed. But having a risk factor, or even many risk factors, does not mean that you will get the disease. And many people who get the disease do not have any known risk factors. Even if a person has a risk factor and gets cancer, it is often very hard to know how much that risk factor might have contributed to the cancer. There are very few known risk factors for CLL.

Certain chemical exposures

Exposure to Agent Orange, an herbicide used during the Vietnam War, has been linked to an increased risk of CLL. Some studies suggest that farming and long-term exposure to pesticides may be linked to an increased risk of CLL, too. More research in this area is needed.

Family history

Close relatives (parents, siblings, or children) of CLL patients have an increased risk for this cancer.


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

Where you come from

CLL is more common in North America and Europe than in Asia.

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

Last Medical Review: 08/05/2013
Last Revised: 11/04/2014