The Causes of Leukemia and Potential Risk Factors

The causes of leukemia are complicated, and medical experts cannot pinpoint causes in all cases. Certain external causes, such as radiation or toxic chemicals, explain some cases. Others can be traced to family history or genetic disorders that damage chromosomes. Some cases, however, cannot be traced to any specific cause whatsoever.

People who have an immediate family member with the disease (children, siblings or parents) are at two to four times greater risk than people with no family history of the disease. For a child whose identical twin develops the disease before six years of age, the risk is 20 to 25 percent higher than in the general population.

 

Certain genetic disorders also increase the likelihood of developing this cancer. The abnormal chromosomes that cause Down's syndrome, for instance, raise the chance of developing the disease. Damage to chromosomes also occurs in Fanconi's anemia, an inherited bone marrow disorder. As with Down's syndrome, people living with Fanconi's anemia have a higher than normal risk of blood cancer.

Leukemia is sometimes associated with translocation of chromosomes. At its simplest, translocation occurs when a portion of one chromosome switches position with another chromosome. The "Philadelphia" chromosome, which occurs due to a translocation between chromosomes 9 and 22, is often found in cases of chronic myelogenous leukemia (CML). Translocation prevents cells from maturing normally and gives them a growth advantage over neighboring cells. These immature cells then begin to "crowd out" normal cells.

Exposure to high levels of radiation can cause leukemia. Higher incidence rates of the disease were reported in Japan after Hiroshima and Nagasaki were destroyed by atomic bombs. Radiation from nuclear energy plant accidents, such as occurred in Chernobyl in 1986, also raise risk levels.

 

Thankfully, such exposure to radiation is uncommon. Evidence exists, however, that the high doses of radiation used in certain medical treatments may trigger the disease in some people.

 

Chemical workers who are exposed to high levels of formaldehyde and benzene are at higher risk than other people. Certain chemotherapy drugs, used to combat cancer, have also been linked to later development of leukemia.

HTLV-1 is a virus that causes human T-cell leukemia, a rare chronic form of the disease. Although HTLV-1 is a virus, no medical research suggests that the virus is contagious through casual contact.

Age plays a role in determining risk factors. The cancer is most often diagnosed in people over age sixty. Adults are ten times more likely to develop the disease than children. Nevertheless, leukemia is one of the most common of childhood cancers.

 

Men are more at risk than women. According to the National Cancer Institute, incidence rates are fifty percent higher for men than women. Ethnicity also plays an important role: Caucasians are at higher risk than other ethnic groups, while people of Japanese, Chinese, and Korean descent are among the lowest risk groups.

For some time, a theory circulated in the media and among the public that exposure to electromagnetic fields could be one of the causes of leukemia. Both everyday electrical appliances and power lines generate electromagnetism. Clinical investigations have not indicated that exposure to electromagnetism is a significant risk.