Spinal Muscular Atrophy (SMA) is a genetic disorder characterized by the degeneration of alpha motor neurons in the spinal cord, leading to progressive muscle weakness and atrophy. We conducted an extensive epidemiological study, collecting prevalent data from various regions and using proxy populations where direct data were unavailable. Our objective was to analyze how global SMA prevalence is shaped by a combination of genetics, healthcare, and socioeconomic factors, including access to costly treatment.
Regional variations exist
Our global analysis suggested that the diagnosed prevalence and distribution of SMA subtypes vary significantly across different regions. In Europe, the prevalence of SMA types 1, and 2 was adjusted for drug-treatment patient shares in Austria and Switzerland, using the data averaged from the EU5 countries, due to similar SMA implementations. In LATAM, countries like Argentina, Brazil, and Colombia reported varying prevalence rates for different SMA subtypes. In APAC, higher-income countries like Hong Kong and Singapore showed different prevalence rates compared to lower-income countries like Indonesia and Vietnam. In Africa, the Middle East, and the Asian Subcontinent, countries like Egypt, India, and Saudi Arabia exhibited unique prevalence patterns influenced by their genetic traits, healthcare systems, and socio-economic factors.
Next, we delved into how SMA prevalence was influenced by the following factors:
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Genetic factors: The role of Hardy-Weinberg equilibrium
SMA is a genetic disease that follows an autosomal recessive pattern. Thus, one of the key genetic principles we relied on is the Hardy-Weinberg equilibrium, which assumes no selection, minimum migration, large population size, and no mutation. By selecting proxy populations with similar genetic backgrounds, we aimed to ensure accurate prevalence estimates. For instance, in Europe, countries like Austria, Belgium, and Switzerland served as proxies for regions with similar genetic characteristics.
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Healthcare systems: a crucial determinant
Regions with advanced healthcare systems and higher screening/detection rates tend to report more data for SMA prevalence estimates. For example, Saudi Arabia boasts a more advanced healthcare system and higher screening/detection rates compared to other Middle Eastern countries.
Innovations in treating SMA have been revolutionary. Two effective treatments are available for SMA, but they differ in their mechanisms and administration methods. One is an antisense oligonucleotide administered via intrathecal injection, while the other is a small molecule drug taken orally, making it easier for patients who cannot receive intrathecal injections. Both therapies target the SMN2 gene to increase levels of the SMN protein, which helps improve muscle and nerve function.
Also available is a gene therapy that delivers a functioning copy of the SMN1 gene to motor neuron cells, addressing the genetic root cause of SMA. The gene therapy has shown remarkable results, outperforming other SMA therapies in terms of effectiveness and setting a new standard for SMA treatment. In a meta-analysis of 57 studies, gene therapy achieved a 95% survival rate and significantly reduced the number of patients requiring ventilatory support. In comparison to the other therapies, gene treatment is more effective in improving motor function and survival rates in infants. However, the availability of these treatments, especially gene therapy, is significantly influenced by favorable reimbursement policies in regions like North America and Europe.
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Socio-economic factors: bridging the gap
Income levels play a critical role in determining access to SMA treatment, creating stark contrasts between high- and low-income regions. In wealthier countries, established healthcare systems and national patient registries lead to higher diagnosis rates and greater access to specialized SMA therapies. In lower-income regions, limited healthcare funding, fewer neuromuscular specialists, and the inflated cost of treatment create significant barriers. Without financial support, many families resort to alternative funding methods, including crowdfunding, to secure therapy. These economic disparities underscore a key challenge in SMA care: ensuring timely diagnosis and access to life-changing treatments, regardless of financial resources.
The need for a multifaceted approach
The interplay of genetic, healthcare, and socio-economic factors creates a complex landscape that requires a multifaceted approach to understanding and addressing SMA prevalence. By accounting for proxy populations and treatment availability, we gain valuable insights into SMA’s global impact.
So, the next time you hear about SMA, remember that it is not just a genetic disorder – it is a global puzzle shaped by a myriad of factors. With continued research and collaboration, we can see how genetics, economics, and access to healthcare shape SMA prevalence and improve the lives of those affected by this challenging condition.
Learn more about how Clarivate helps life science companies accurately size their markets using industry standard epidemiology intelligence here: Epidemiology Data, Resources & Analytics | Clarivate
This post was written by Alex Li, MD, PhD, Senior Epidemiologist, and Shyama Ghosh, PhD, Senior Principal STEM Content Analyst.
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