Although there is no proven cause for leukemia, the disease is known to affect people of both sexes and all ages. It is also observed that leukemia affects more males than females, and is more often found in white people than in black people. On a positive note many people with one or more of known risk factors for leukemia never develop the disease, but most people who do develop the disease have no risk factors at all. Researchers have identified several possibilities for leukemia which are:

	Age
	Researchers believe that the chances of a normal gene changing into a cancerous gene increases with age. More than half of people who develop leukemia are over the age of 60.
	Smoking
	There have been reports of an increased risk of AML with cigarette smoking because it may trigger certain changes in a cell's genes.
	Ionizing radiation
	A small percentage of leukemia cases are linked to exposure to high doses of radiation. For example, the survivors of the atomic bomb explosions at Nagasaki and Hiroshima in 1944 subsequently saw an increased incidence of leukemia. However, it has not been proven that exposure to large amounts of low-energy radiation from electric appliances, diagnostic imaging tests, or living near power lines will cause leukemia.
	Certain genetic conditions
	Scientists do know that most types of leukemias are associated with specific gene mutations. People who have rare genetic syndromes are at a higher risk of developing the disease. One example is Down's Syndrome, in which there is a 20-fold risk of getting leukemia. Studies have shown that sex and ethnicity are factors in the disease as well. It is observed that leukemia occurs in males more often than in females, and in white people more often than in black people. The incidence of leukemia is high in Jewish people from Eastern Europe, but low in Asians.
	Chemical exposure
	Workers who have a long-term exposure to high levels of solvents such as benzene have a high rate of leukemia. Benzene is used in making medicines, dyes, and many other products.
	Drug therapy
	Certain drugs used to treat cancer called alkylating agents may also cause leukemia anywhere from two to nine years following treatment for various forms of cancer. The antibiotic chloramphenicol was associated with an increased risk of childhood ALL in mainland China.
	Rare viruses
	Human T-cell leukemia virus (HTLV-1) has been associated with the adult T-cell leukemia/lymphoma, which is often seen in geographical areas like the Caribbean and Japan.