Multiple myeloma is a type of cancer that develops from plasma cells, which are a type of white blood cell found in the bone marrow. These plasma cells normally produce antibodies to help the body fight infections, but in multiple myeloma, they become abnormal and multiply uncontrollably. This accumulation of cancerous plasma cells can crowd out healthy blood-forming cells and produce abnormal proteins, leading to various health issues affecting bones, kidneys, and blood. This article will explore the incidence of multiple myeloma, examining current rates, demographic influences, and trends over time.
Understanding Multiple Myeloma and Incidence
In multiple myeloma, these abnormal plasma cells accumulate in the bone marrow and can produce dysfunctional antibodies, known as M proteins. These M proteins can lead to kidney problems and overly thick blood.
In the context of cancer statistics, “incidence” refers to the number of new cancer cases diagnosed within a specific population over a defined period, typically a year. This differs from “prevalence,” which represents the total number of existing cases in a population at a particular point in time, including both new and previously diagnosed cases. Understanding incidence is important for public health because it helps researchers track how frequently a disease is occurring, identify populations at higher risk, and assess the effectiveness of prevention and early detection strategies.
Current Incidence Rates Worldwide
Globally, multiple myeloma accounted for an estimated 188,000 new cases in 2022, with about 121,000 deaths. The age-standardized incidence rates (ASIR) for multiple myeloma vary significantly across different regions of the world, reflecting disparities in diagnosis and treatment.
For instance, North America generally shows the highest incidence rates, with an age-standardized rate of 4.8 cases per 100,000 population. Europe and Oceania also exhibit relatively high incidence rates, with ASIRs of 2.8 and 3.7 per 100,000, respectively. In contrast, regions like Africa and Asia tend to report lower incidence rates, with ASIRs of 1.1 and 1.2 per 100,000 population.
These lower figures may be influenced by factors such as underdiagnosis and reporting issues in some areas. These variations highlight the complex interplay of genetic predispositions, socioeconomic conditions, and access to healthcare in influencing disease outcomes worldwide.
Demographic and Risk Factors Influencing Incidence
Age is a significant demographic factor influencing multiple myeloma incidence, with the risk increasing substantially as individuals get older. Most diagnoses occur in people aged 65 years or older, and fewer than 15% of cases are diagnosed in individuals younger than 55. The median age at diagnosis for multiple myeloma in the U.S. is around 69 years.
Sex also plays a role, with men generally having a slightly higher incidence of multiple myeloma than women, being about 1.5 times more likely to develop the disease. Racial and ethnic background also show disparities in incidence rates. Multiple myeloma is more than twice as common in Black individuals compared to White individuals, and Black Americans often receive a diagnosis at a younger average age, typically 5 to 10 years earlier. While the exact reasons for this racial disparity are not fully understood, some scientists suggest it may relate to certain genetic variations.
Beyond demographics, several other risk factors contribute to the incidence of multiple myeloma. Having a history of monoclonal gammopathy of undetermined significance (MGUS), a pre-malignant plasma cell disorder, significantly increases the risk of developing multiple myeloma. Family history also plays a role, as individuals with a parent or sibling diagnosed with multiple myeloma have a nearly four-fold increased risk.
Excess body weight and obesity are also associated with a higher incidence of multiple myeloma. Furthermore, exposure to certain chemicals, such as those found in herbicides like Agent Orange, or occupational exposures in fields like farming, petroleum production, or carpentry, may elevate the risk. A weakened immune system, as seen in individuals with HIV or those taking immunosuppressants after organ transplants, also increases the likelihood of developing multiple myeloma.
Trends in Incidence Over Time
The incidence of multiple myeloma has shown varying trends over recent decades. While the age-adjusted incidence rates in the United States were relatively stable between 2013 and 2022, there have been observed increases in crude incidence globally. This global rise in crude incidence is largely attributed to the aging global population, as multiple myeloma is predominantly a disease of older adults.
Improvements in diagnostic methods and increased awareness are also thought to contribute to the observed increase in reported cases. For example, a 2020 study noted that incidence rates are predominantly rising in developed countries, which often have better access to diagnostic resources and quality healthcare.
While the age-standardized incidence rate in the United States decreased by 10.33% between 1991 and 2021, with a more pronounced decline in females, the number of new cases is still projected to increase due to demographic shifts. The overall number of multiple myeloma patients is increasing in the general population, not only due to aging demographics but also because modern treatments allow patients to live longer with the disease.