Global study shows how a country’s wealth affects SMA diagnosis rates
More cases ID'd, treated in wealthier regions; underdiagnosis in poorer nations
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Spinal muscular atrophy (SMA) is more common in wealthier countries across the globe, likely reflecting increased access to diagnostic tools, newborn screening, and modern treatments.
That higher prevalence — the total proportion of a population living with a specific condition at a given time — would normally suggest a greater overall disease burden of SMA in wealthier countries. However, the researchers behind this global analysis noted that their findings also highlight a likely underdiagnosis of the genetic disease in poorer nations.
Analyzing data from 204 countries and territories, the researchers estimated a global SMA prevalence of 0.01%. That means the condition affects 1 in every 10,000 people worldwide.
The highest rates were reported in high-income regions, including the U.S. and Western Europe. The lowest prevalence was seen in South Asia and subSaharan Africa, where, the researchers noted, limited healthcare resources may lead to underdiagnosis.
“Substantial association was found between SMA prevalence and socioeconomic indicators … highlighting global disparities in diagnostic capacity and patient survival,” the researchers wrote, noting “major geographic inequities.”
“These estimates may support efforts to strengthen newborn screening, improve diagnostic infrastructure, and inform planning for SMA care and resource allocation across diverse health-care settings,” the scientists wrote.
The study, “Global prevalence of spinal muscular atrophy in 204 countries and territories, 1960-2024: a systematic review and Bayesian modelling study,” was published in the journal Pediatric Neurology.
Despite huge advances in the diagnosis and treatment of SMA in recent decades, the condition’s global prevalence remains poorly characterized, the researchers noted. This is mostly due to substantial geographic disparities in diagnosis, linked in part to wide gaps in newborn screening infrastructures.
Also, per the team, most studies are based on data from high-income regions such as North America and Western Europe, while other regions have little to no reported data.
Overall, “epidemiologic evidence remains limited and geographically skewed,” the researchers wrote.
Review looked at rates of SMA across more than 200 countries
To learn more, an international team of scientists conducted a systematic review of studies reporting SMA prevalence across more than 200 countries and territories from 1960 to 2024.
A total of 58 studies were selected for the review, mostly from high-income countries, including the U.S., Canada, Japan, and several European nations. Large regions in Africa, South Asia, and Latin America had one or no eligible studies.
The global prevalence of SMA was estimated at 0.01%. The neuromuscular disease was most common in high-income countries (0.027%) and least frequent in South Asia and subSaharan Africa (0.002%). In addition, prevalence in newborns was estimated at 0.02%, and in children at 0.008%.
Regional estimates showed substantial variation in newborns and children. The highest prevalence was reported in Western Europe — 0.043% in newborns and 0.11% in children — while the lowest was in South Asia and subSaharan Africa, at 0.003% in newborns and 0.008% in children.
Disparities were also seen when looking at countries. Among newborns, Sweden was the country with the highest percentage of SMA cases (0.156%), followed by Norway, Iceland, Ireland, and France. In contrast, the lowest prevalence was reported in Algeria, Bahrain, Egypt, Iran, and Iraq. Similar results were estimated for children.
Socioeconomic factors significantly linked to SMA prevalence
Across countries, higher socioeconomic indicators were significantly associated with a higher SMA prevalence in both newborns and children. Among the socioeconomic indicators were the socio-demographic index — a composite measure of income, education, and fertility — an index assessing healthcare access and quality, and the gross domestic product per capita.
According to the researchers, several factors may explain these findings, including higher diagnostic capacity and access to genetic testing in high-income countries, as well as the greatest implementation of newborn screening programs that include SMA.
This disparity [across regions] implied that in countries with high-resource settings, almost all affected infants were now diagnosed (often presymptomatically), while in regions with low-resource settings … many cases were not identified and diagnosed.
Importantly, per the team, countries with more limited resources usually lack registries and surveillance systems for newborns.
This “[results] in many infants with lethal SMA dying at home without ever receiving an official diagnosis or cause-of-death record,” the team wrote. As such, these children’s lives were not counted in their country’s tallies, the researchers noted.
“This disparity implied that in countries with high-resource settings, almost all affected infants were now diagnosed (often presymptomatically), while in regions with low-resource settings … many cases were not identified and diagnosed,” the team wrote.
Survival differences associated with greater access to modern treatments and supportive care in high-income countries also affect how frequent SMA is, as children with the disease live longer, the investigators noted.
“Therefore, countries with higher socioeconomic status not only identify more cases of SMA but also sustain them longer, magnifying prevalence relative to vulnerable regions where most cases go untreated,” the researchers wrote.
