ON THIS PAGE: You will find out more about the factors that increase the chance of developing CLL. To see other pages, use the menu on the side of your screen.
A risk factor is anything that increases a person’s chance of developing cancer. Although risk factors often influence the development of cancer, most do not directly cause cancer. Some people with several risk factors never develop cancer, while others with no known risk factors do. However, knowing your risk factors and talking about them with your doctor may help you make more informed lifestyle and health care choices.
The cause of CLL is unknown. There is no evidence that exposure to radiation, chemicals, or chemotherapy increases a person’s risk of developing CLL. However, the following factors may raise a person’s risk of developing CLL:
Family history. Although it is uncommon, more than one close relative may develop CLL or some other lymph-related cancer. People with a first-degree relative with CLL, such as a parent, sibling, or child, are two to four times more likely to develop the disease. In order to learn more about families with a history of CLL, there is a registry of such families  at the National Cancer Institute.
Age. CLL is most common in older adults, is rare in young adults, and hardly ever develops in children. About 90% of people diagnosed with CLL are older than 50. The average age of people diagnosed with CLL is close to 70.
Gender. Men develop CLL more often than women.
Race/Ethnicity. B-cell CLL is more common in people of Russian and European descent, and hardly ever develops in people from China, Japan, or Southeast Asian countries. It also occurs commonly in black people. The reason(s) for these differences is not known.
Agent Orange. The U.S. Department of Veterans Affairs lists CLL as a disease associated with exposure to Agent Orange , a chemical used during the Vietnam War.
The next section in this guide is Symptoms and Signs  and it explains what body changes or medical problems this disease can cause. Or, use the menu on the side of your screen to choose another section to continue reading this guide.