Leukemia: Risk Factors

Age. ALL occurs mostly in children, with a peak age range of 3 to 5 years. AML incidence increases with age, peaking at about age 60. CLL and CML are also both diseases of adults, with onset most common in patients older than 50.

Gender. ALL, AML, and CLL are more common in males.

Race/Ethnicity. AML is more common in Caucasian populations, and CLL is more common in Eastern European Jews.

Viral exposure. Exposure to human T-cell lymphoma/leukemia virus (HTLV-1) and Epstein-Barr virus may increase the risk of some ALL subtypes.

Radiation exposure has been associated with ALL. Ionizing radiation is associated with increased risk for AML, and exposure to ionizing radiation is the only known risk factor for CML.

Tobacco. For AML, tobacco use is a strong risk factor, accounting for about 1 in 5 cases.

Chemicals. Exposure to benzene, petroleum products, and pesticides is associated with increased risk for AML. Prior chemotherapy is also a risk factor and accounts for up to 10% of AML cases. Some studies suggest that herbicides (including Agent Orange) and insecticides may increase risk for CLL.

Family history. For CLL, risk is increased in first-degree relatives of affected patients.

Down syndrome. Children with Down syndrome are at increased risk for both AML and ALL.