A risk factor is something that affects a person's chance of getting a disease. Some risk factors, such as smoking, can be controlled. Others, like a person's age or race, can't be changed. But risk factors don't tell us everything. People who have no risk factors can still get the disease. Also, having a risk factor, or even several, does not mean that a person will get the disease.

Scientists have found a few risk factors that may make a person more likely to get multiple myeloma. These are the known risk factors for multiple myeloma:

Age and gender: Age is the biggest risk factor for multiple myeloma. Very few cases are found in people younger than 35. Most people with this cancer are over 65 years old. Men are slightly more likely to get multiple myeloma than women.

Race: Multiple myeloma is almost twice as common among black Americans as white Americans. The reason is not known.

Radiation exposure: Exposure to radiation may increase the risk of multiple myeloma. At most, this accounts for a very small number of cases.

Family history: This cancer seems to run in some families. If a person has a parent, brother, or sister with the disease, their risk of getting it is 4 times higher than that of other people. But this is rare. Most patients have no other relatives with the disease.

Exposure on the job: Some studies suggest that workers in some oil-related industries may be at a higher risk.

Weight: A study by the American Cancer Society found that being overweight increases a person's risk of getting this cancer.

Other plasma cell diseases: Many people with other plasma cell diseases will develop multiple myeloma later.

While the exact cause of multiple myeloma is not known, scientists are learning how changes in DNA can cause plasma cells to become cancer. DNA is the substance that tells our cells how to behave. Cancer can be caused by changes (mutations) in the DNA that controls cell growth.

Last Medical Review: 03/13/2009
Last Revised: 05/06/2009