Multiple myeloma develops when white blood cells called plasma cells develop gene mutations. These mutations cause the cell to begin growing abnormally and turn cancerous.
Gene mutations build up in cells over time. They become more numerous as a person gets older. Therefore, older adults are more likely to have gene mutations that lead to myeloma than are children or younger adults.
Myeloma can also affect younger adults, but this is rare. About 1 out of 50 people with myeloma are under the age of 40.
Older people also have a higher risk of developing the two plasma cell disorders that can lead to multiple myeloma: monoclonal gammopathy of undetermined significance (MGUS) and smoldering myeloma. The average age at diagnosis for MGUS is also 70, although most people have the condition for at least 10 years before they are diagnosed. Half of people with smoldering myeloma are 67 or older at the time of diagnosis.
In order to understand the link between myeloma and aging, it helps to know how this condition develops. Multiple myeloma develops in the bone marrow — the spongy tissue found within certain bones.
In healthy people, plasma cells in the bone marrow help make proteins called antibodies that help the immune system fight off germs, such as bacteria and viruses. In people with multiple myeloma, the plasma cells become abnormal. They divide too quickly, making many copies of themselves and forming tumors in the bones or in soft tissues. Abnormal plasma cells also make a non-functional antibody called M protein.
Myeloma is thought to develop due to gene changes that affect the process of cell division — when a parent cell divides in order to form two new cells. Normally, certain genes act as brakes, preventing a cell from dividing too often or in an uncontrolled way. When these genes are damaged due to mutations, a cell is able to divide and produce new cells more often than it should.
Gene mutations build up over time. Although myeloma-causing mutations could occur at any point in a person’s life, the chances of this happening rise the older a person gets.
Several different factors can lead to gene changes. Some gene mutations are inherited — passed down within families — but this is not usually the case for myeloma. Most people with myeloma don’t have a family history of the condition. Instead, the gene mutations that cause multiple myeloma usually develop over the course of a person’s life.
Genes can be damaged when a cell is exposed to:
That is why some of these factors, such as radiation or chemical exposure, lead to an increased risk of multiple myeloma and other types of cancer.
Gene mutations can also develop during the process of cell division. As a cell divides, the parent cell copies its DNA, the molecule that contains the cell’s genes. It then passes on one copy to each of the two new cells. Occasionally, the cell makes a mistake when copying a particular gene, causing the gene to become mutated. Additionally, the cell may incorrectly divide up the DNA copies between the two cells, leading to larger-scale gene changes.
The older a person gets, the more likely it is that they have been exposed to myeloma risk factors or that their cells have made mistakes during cell division. Therefore, the risk of having cancer-causing gene changes increases with age.
Many types of cells don’t frequently grow and divide after a person has finished growing into an adult. Therefore, there may be fewer opportunities for cell division mistakes in these cells.
However, the body is constantly making new blood cells. This means that new mutations are regularly forming and being passed on to other cells. Researchers estimate that by the time a person turns 60, these quickly dividing cells could contain tens of thousands of mutations. This could lead to different types of blood cancers, including myeloma as well as leukemia and lymphoma.
Altogether, the older a person gets, the more mutations their blood cells will collect. The more mutations a cell contains, the higher the chances that it will turn cancerous.
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