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First estimate of autism prevalence in Mexico pegs number at 1 in 115

Study results provide foundation for building national system to address huge need for services; a model for other Latin American countries
January 26, 2016

The first scientific estimate of autism’s prevalence in Mexico pegs the number at 1 in 115. While the number may be an underestimate, it provides a solid foundation for government leaders and agencies that have expressed eagerness to understand and meet their nation’s need for autism services.

Funded by Autism Speaks, the study appears this week in the Journal of Autism and Developmental Disorders.

At just under 1 percent, the estimate is roughly in line with the “1 in 100” figure for Hispanic children diagnosed with autism in the United States. Autism’s overall prevalence in the United States is an estimated 1 in 68. Experts generally agree that the lower Hispanic number reflects a lower rate of identifying autism – not a true lower prevalence. The same may be true of the new estimate for Mexico.

Establishing a clear picture of need
Most importantly, the researchers say, the study results give Mexican public health agencies their first clear picture of the need for autism services in their country.

“These results tell us that there are around 400,000 children and adolescents in Mexico who are affected by autism and in need of services,” says lead researcher Eric Fombonne, of Oregon Health & Science University.

“Of particular concern is that Mexican children with autism are being diagnosed at a very late age – indicating lost opportunities for early interventions and increased burden on families,” Dr. Fombonne adds. In the study, nearly 78 percent of the children with autism did not receive their diagnosis until age 3. Another 22 percent went undiagnosed until age 5.

Autism can be reliably diagnosed as early as ages 18 to 24 months, though even in the U.S. the average age of diagnosis remains closer to 4 years of age.

A model for other nations

“This study not only provides a much-needed platform for autism advocacy and policy planning in Mexico, it also serves as a model for much needed autism prevalence research across the Americas.,” says Michael Rosanoff, Autism Speaks director of public health research.

Through its Global Autism Public Health (GAPH) initiative, Autism Speaks has forged partnerships with 70 countries to help them create systems of care and support based on culturally sensitive and economically viable methods. This includes Mexico and 11 countries in Central and South America.

Study methods
To make their estimate, the researchers focused on Leon, a city of nearly 1.6 million people in central Mexico, with demographics similar to the country as a whole.

The study combined two methods for identifying children with autism.

First, they looked for established autism diagnoses in the service records of 8 year olds attending special education programs. This is similar to the methods used by the U.S. Centers for Disease Control and Prevention (CDC) to estimate autism’s prevalence in the United States.

Second, they used the direct survey method pilot tested by an Autism Speaks-funded study in South Korea in 2011. This involved conducting in-person autism screenings of students in general classrooms (with parent permission), followed by a full evaluation for autism. These school children had gone undiagnosed before the study screenings.

Most of the children that the study identified as having autism (57.5 percent) were among the previously undiagnosed students in general classrooms. The other 42.5 percent were among those in special education programs.

Just over 30 percent of the children identified as having autism also had intellectual disability. This is generally in line with rates in the United States and elsewhere. The study also found the 4-to-1 boy to girl ratio that’s been seen in virtually all prevalence studies to date.

Autism Speaks will continue to offer its guidance and support to Mexican public health agencies and Mexican autism-advocacy groups as they work to develop and expand services to meet the need of individuals and families affected by autism in their nation.

Learn more about Autism Speaks Global Public Health initiative here.

Subscribe to a daily feed of Autism Speaks Science News here.