Chronic lymphocytic leukemia (CLL) is the most common type of adult leukemia in the United States.

Leukemia is a group of cancers that develop in blood cells. CLL develops in a type of white blood cell called lymphocytes. The rapid division of lymphocytes can crowd out healthy blood cells. Over time, this can lead to symptoms like:

  • Anemia.
  • Irregular bruise
  • There are frequent infections.

“Researchers have identified risk factors that increase your chances of developing CLL, but they don’t know the exact cause. Read on to learn more.”

Potential risk factors for CLL have been identified.

Family history

A family history of CLL is the strongest known risk factor. It’s estimated that people with a parent, siblings, or child with CLL have an 8.5 times higher risk of developing CLL than somebody without a family history.


The risk of developing CLL rises exponentially with age and is highest among people over the age of 70. About 90 percent of people who develop CLL are over the age of 50.

The average age of onset is 72.

Exposure to chemicals

Exposure to certain chemicals can increase your risk of CLL.

One chemical associated with an increased risk of CLL is Agent Orange. This herbicide was used during the Vietnam War to clear leaves and vegetation. Production stopped in the United States in the 1970s.

In a 2018 study, researchers found Vietnam veterans exposed to Agent Orange developed CLL at a younger age than veterans not exposed to Agent Orange:

  • Half of veterans exposed to Agent Orange who developed CLL were younger than 60.
  • Half of veterans who did not get exposed to Agent Orange were younger than 70.

The researchers found that exposure to Agent Orange was not associated with a poorer outlook.

Other studies have found evidence of a potential link between CLL and some other herbicides, pesticides, and agricultural agents. The frequency and duration of exposure to these chemicals are thought to contribute to the risk.

According to the American Cancer Society, rates of leukemia — particularly acute myeloid leukemia — are higher in workers exposed to high levels of benzene. Benzene is used in industries such as leather manufacturing, oil refining, and rubber manufacturing.

Some studies suggest a link between benzene exposure and CLL.

Biological sex

The risk of developing CLL is about twice as high in men than in women, but it’s still unknown why men are at a higher risk.

In a 2019 study, researchers found evidence that differences in DNA methylation between sexes may play a role. DNA methylation is a process where a methyl group is added to a DNA molecule. It’s involved in many bodily functions and health problems.


Rates of CLL are higher in North America and Europe compared to Asia. CLL is most common in people who are white or of Eastern European, Russian, or Jewish descent.

Asian people in the United States have the same rates of CLL as Asian people in Asia. This suggests that genetics play a role in racial differences.

CLL may have different outlooks in different races. Studies suggest that Black people may have poorer overall survival than other groups.

“Researchers don’t know what causes CLL. A combination of genetic and environmental factors is likely to contribute.”

CLL is a form of cancer that develops when genetic changes cause cells to replicate uncontrollably. These cells are a type of white blood cell.

A loss of part of chromosome 13 is the most common genetic mutation in people with CLL. Loss of part of chromosomes 11 or 17 are also common. In some cases, there may be an extra chromosome 12.

Many of the risk factors for CLL, like your genes or biological sex, are out of your control. Most people with CLL have no known risk factors.

You may be able to lower your chances of developing CLL by:

  • avoiding contact with benzene
  • Maintaining a healthy body weight is important.
  • Reducing contact with pesticides and herbicides.
  • When you come into contact with potentially cancer-causing chemicals, wear protective clothing.

Does having CLL put you at high risk for COVID-19?

Research suggests that people with CLL may be more likely to develop COVID-19 due to advanced age, disease-related immunosuppression, and treatment-related immunosuppression.

Taking precautions, like wearing a mask in public spaces, can help you minimize your chances of developing illness.

What are the common symptoms of CLL?

Symptoms of CLL may not be noticeable in the early stages. It may cause symptoms as it progresses.

What are the treatment options for CLL?

Treatment for CLL depends on factors such as how far along your cancer has progressed and your overall health. Options include:

What’s the most common cause of death in CLL?

In a 2021 study, researchers found that the most common cause of death among people with newly diagnosed CLL was:

Cause of death in people with CLL Percentage
complications related to disease progression 34.6%
infection 5.6%
second cancer 16.4%
CLL-unrelated death 20.6%
unknown 22.7%

What’s the outlook for CLL?

The survival rate for CLL is higher than many other types of leukemia and cancer. Half of people diagnosed with CLL live at least 10 years. Some people live 20 years or more.

CLL is the most common type of leukemia in the US. Researchers have identified some risk factors for CLL.

A family history of CLL is the most important risk factor. Increased age, male sex, and exposure to some chemicals are some of the risk factors.

There are a lot of risk factors for CLL that are not yours to control. Exposure to pesticides and other potentially harmful chemicals may help reduce your chances of developing CLL and other cancer.