Multiple myeloma is a type of cancer that affects plasma cells, which are a kind of white blood cell found in the bone marrow. These plasma cells normally help fight infections by producing antibodies. In multiple myeloma, however, these cells become abnormal, multiply uncontrollably, and produce faulty proteins that can damage bones, kidneys, and blood cells. This disease is notably more common in seniors, and understanding why requires looking at several biological, environmental, and lifestyle factors that accumulate with age.
One of the main reasons multiple myeloma is more common in older adults is related to the natural aging process of the immune system and bone marrow. As people age, their immune system gradually weakens—a process called immunosenescence. This weakening means the body is less efficient at detecting and destroying abnormal cells, including those that might turn cancerous. The bone marrow, where plasma cells live and multiply, also undergoes changes with age. It becomes less effective at producing healthy blood cells and more prone to errors during cell division. These errors can lead to mutations in plasma cells, increasing the risk that they become malignant and develop into multiple myeloma.
Another important factor is the presence of a precursor condition called monoclonal gammopathy of undetermined significance (MGUS). MGUS is a benign disorder where abnormal plasma cells produce a small amount of abnormal protein, but it does not cause symptoms or damage. MGUS is found in about 3% of people over 50, and its prevalence increases with age. While MGUS itself is not cancer, it can progress to multiple myeloma in a small percentage of cases. Because MGUS becomes more common as people get older, the risk of progression to multiple myeloma naturally rises with age.
Lifestyle and environmental exposures accumulated over a lifetime also contribute to the increased risk in seniors. Factors such as obesity, long-term exposure to certain chemicals (like pesticides and insecticides), radiation, and even family history can influence the likelihood of developing multiple myeloma. Obesity, in particular, has been shown to increase the risk of MGUS progressing to multiple myeloma. Excess weight causes chronic inflammation and hormonal changes that may promote the growth of abnormal plasma cells. Since older adults are more likely to have lived with these risk factors for decades, their cumulative effect raises the chance of developing the disease.
Genetic and racial factors also play a role. For example, African American individuals have a higher incidence of multiple myeloma compared to Caucasians, and they are more likely to experience progression from MGUS to multiple myeloma. This disparity may be due to genetic predispositions combined with environmental and socioeconomic factors. Since the risk increases with age, these differences become more apparent in the senior population.
The median age of diagnosis for multiple myeloma is around 70 years old, which aligns with the biological and environmental factors accumulating over time. The disease is rare in younger people, partly because their immune systems and bone marrow are more robust and less prone to the mutations that cause cancerous plasma cells to develop.
In addition to the biological reasons, older adults often face challenges that complicate the diagnosis and treatment of multiple myeloma. Symptoms such as bone pain, fractures, anemia, and kidney problems may be mistaken for normal aging or other chronic conditions, delaying diagnosis. Furthermore, older patients may have other health issues that limit treatment options or make aggressive therapies riskier. This complexity underscores why multiple myeloma is both more common and more difficult to manage in seniors.
In summary, multiple myeloma’s higher prevalence in seniors is due to the natural decline in immune function and bone marrow health with age, the increased presence of precursor conditions like MGUS, lifelong exposure to risk factors such as obesity and environmental toxins, and genetic predispositions. These factors combine over decades, making older adults more susceptible to developing this blood cancer.