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The age of onset, sex, clinical features, and other demographic characteristics of multiple sclerosis (MS) in Latin America largely mirror those seen in MS patients in North America and Europe.
Although some Latin American countries are now collecting greater amounts of data on MS, demographic information remains scarce across the region.
To get a better sense of these demographics and how they compare to other world regions, Fernando Gracia, MD, of ULACIT University, in Panama, reviewed and summarized the available literature on the topic.
These data were presented at the Americas Committee for Treatment and Research in Multiple Sclerosis (ACTRIMS) Forum 2021, held virtually from Feb. 25 to 27, in the talk “Spectrum of MS Demographics in LATAM Population.”
Latin America has an estimated population of more than 605 million people, covering 36 countries and six territories, Gracia said.
The prevalence of MS he described as “low to very low” across Latin America, suggesting a regional influence of environmental and genetic factors.
Rates vary from 0.75 per 100,000 people in Guayaquil, Ecuador, at the low end, to 38.2 in Buenos Aires, Argentina, at the high end. The only higher ratio was the cumulative lifetime prevalence of 68.8 recorded in Puerto Rico.
Gracia noted that Latin America has a “complex genetic admixture [that] arises from multiple divergent population ancestries in different countries including: Native Americans, Caucasians [Europeans], and Africans.”
People of mestizo — broadly meaning of mixed European and indigenous American descent — and African ancestry appeared to be most susceptible to MS, possibly due to the introduction of the European HLA-DRB1*1501 gene (a known genetic risk factor for MS). Conversely, American indigenous ancestry appears to confer a measure of protection.
Familial MS appears less frequent in the Latin America region, although few studies report on it. Rates reported for Mexico were 3.3%, for Brazil 6.1%, and for Argentina 10.5%.
At least twice as many females as males have MS diagnoses.
Average age at disease onset varied widely across countries, from 27–28 years of age in Mexico to 41 years in Puerto Rico.
The age of onset among Hispanics (Latin Americans) in the U.S. — based on data from the North American Research Committee on MS (NARCOMS) registry — was reported to be 28.6, and 30.1 for non-Hispanic whites. Studies in the U.S. further showed that Hispanic patients tended to have a lower MS risk compared with Caucasians, but a higher risk than do Asians.
Relapsing-remitting MS (RRMS) appeared as the most frequent clinical form of the disease, accounting for approximately 80% of cases. Secondary progressive MS (SPMS) accounted for roughly 15% of cases, and primary progressive MS (PPMS) averaged 5% to 10%.
As an example of these estimates, a Central American-Caribbean case series found that 90% of patients had RRMS and 10% had progressive MS. Similarly, a Mexican study identified 82% of its patients with RRMS, 13.9% with SPMS, and 0.8% with PPMS.
Risk factors for a poorer MS prognosis in Latin America appear to include older age at onset, male sex, higher relapse rate, greater lesion load, motor/cerebellar system affected, substantial disability after five years, African-American ancestry, and smoking and obesity.
“The factors influencing prognosis in MS — a better prognosis or worse prognosis — are more or less the same in the LATAM [Latin American] population than in other regions of the world, like Europe and North America,” Gracia said.
Based on these findings, “we can say that the demographic spectrum of multiple sclerosis in the LATAM population seems to be similar to the North American and European [populations, in terms of] gender, age of onset of the disease, [disease] phases, phenotypes, and clinical characteristics,” Gracia said.
Risk factors for a poorer MS prognosis also appeared similar to those of MS populations elsewhere, as did responses to different disease-modifying therapies. However, Gracia noted that controlled studies are needed to confirm both of these points.
Gracia also emphasized that there “are distinct environmental and ethnic characteristics in LATAM that differ from other world regions and probably explain the lower regional prevalence and incidence of MS.”
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