Sickle cell disease prevalence: How common is SCD in the US, worldwide?
Fact-checked by The prevalence of sickle cell disease (SCD) varies depending on factors like location, race, and ethnicity.
Incomplete SCD statistics and data make it difficult to estimate the global burden of the disease and understand its prevalence, or how many people at a given point in time have the disease. However, this understanding is key for making data-based decisions about resources and supporting the development of more treatments and screening strategies.
How common is sickle cell disease?
SCD is a blood disorder caused by genetic mutations inherited from a person’s biological parents. To develop SCD, a person must inherit two gene copies containing a mutation — one from each biological parent. A person who inherits just one mutated gene copy has sickle cell trait (SCT), meaning they usually don’t develop symptoms, but can still pass the disease-causing mutation to their biological children.
SCD is rare in many places, including the U.S., and is much more common in certain communities where SCT is more prevalent.
The incidence of SCD, or how many new cases emerge in a specific time frame, has stayed relatively stable in the U.S. in recent decades. Globally, however, SCD incidence is increasing. Experts believe this may be related to population growth in areas where the disease is more common. The increased number of SCD cases may also reflect emerging screening programs, which are enabling SCD to be diagnosed earlier and more accurately.
Sickle cell disease prevalence in the United States
Approximately 100,000 people are living with SCD in the U.S. Government agencies define a rare disease as one that affects fewer than 200,000 people in the country, so SCD meets this definition. However, it is still the most common inherited blood disorder in the country.
Studies have suggested that for every 100,000 babies born in the U.S., 48 to 54 have SCD and 1,550 to 1,681 have SCT.
Global prevalence of sickle cell disease
An estimated 7.74 million people globally were living with SCD in 2021, according to a large international study.
A review of several studies found that approximately 191 of every 100,000 children born globally have SCD, and 3,870 have SCT. This type of statistic is called birth prevalence. The approximate regional birth prevalence of SCD varied by region, being highest in Africa (1,321 per 100,000 people) and the Middle East (218 per 100,000 people).
Who is most at risk of sickle cell disease?
While people of any race or ethnicity can get SCD, the disease is much more common in people with ancestors from:
- sub-Saharan Africa
- South or Central America
- the Caribbean
- the Middle East and Mediterranean
- India
These are regions where, historically, malaria was very prevalent. Malaria is an infectious disease spread by mosquitoes that can be life-threatening without treatment.
Researchers have found that SCT can help protect people against severe malaria infections without the health concerns associated with SCD. This means that in places where malaria is a major concern, people with SCT have a greater chance of survival. Because of this, generations of people in these regions evolved to be more likely to have SCT.
However, if two people with SCT have a child, there is a 25% chance that the child will have SCD. So, as SCT became more common, so did SCD.
In the U.S., SCD prevalence varies by race and ethnicity. It is most prevalent among non-Hispanic Black and African American communities. The birth prevalence of SCD is over five times as high in these communities when compared with the overall U.S. birth prevalence. Approximately one out of every 365 Black or African American babies has SCD, and one out of every 13 has SCT.
Globally, SCD is most common in sub-Saharan Africa. The birth prevalence of SCD is nearly seven times higher in Africa than the world as a whole, and nearly 25 times higher than in North America.
Why prevalence estimates can vary
Several factors can influence prevalence estimates, leading to variability in statistics. These include:
- Regional, ethnic, and racial variance: Because the disease is more prevalent in certain communities, statistics vary naturally.
- Data sources and quality: Some governments collect public health data about SCD, while estimates in other regions may rely on data from other sources.
- Newborn screening: In areas where newborn screening for SCD is common or universal, prevalence estimates may appear higher because more people are diagnosed with the condition.
How newborn screening affects diagnosis and data
Newborn screening programs typically use simple blood tests to screen infants for signs of SCD or SCT. If test results suggest that SCD or SCT is present, doctors may recommend follow-up testing.
Broadly, this enables earlier diagnosis, plus more effective monitoring and preventive care strategies. Additionally, early diagnosis may help people with SCD and SCT access important educational resources and genetic counseling to help them make informed family planning decisions.
Countries with stronger screening programs tend to have more accurate prevalence data, because more cases are diagnosed. Without newborn screening, underdiagnosis may reduce the accuracy of prevalence estimates.
Experts say that SCD newborn screening is a feasible and effective strategy to improve diagnosis and data accuracy, including in lower-resource areas. Directing more funding to places where SCD is prevalent, but the public health infrastructure is more limited could help improve diagnosis and statistics globally.
Why better sickle cell disease data matters
Globally, there are areas where SCD data is extremely limited, which means that scientists and public health experts have a less complete view of the disease’s outcomes and burdens. Ultimately, better data could support a stronger understanding of SCD risk factors and improve outcomes for people living with the condition.
Good data also helps governments and organizations make evidence-based decisions about how to allocate resources and design interventions. For example, it could help determine where prevention and screening programs would have the highest impact.
Additionally, high-quality data could help researchers learn more about different types of SCD. Because some types are relatively uncommon, broader and more complete data stemming from many sources and larger populations may yield important new insights.
Sickle Cell Disease News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.
