South Korea study raises doubts about prevalence estimates elsewhere
South Korea just sent autism prevalence rates surging north. Autism spectrum disorders affect an estimated 2.64 percent of the nation’s schoolchildren, or about 1 in 38 youngsters, a new study finds.
That’s a considerably higher figure than has been reported in the United States, England and elsewhere, where prevalence estimates range between 0.07 percent and 1.8 percent. A 2006 report from the U.S. Centers for Disease Control and Prevention estimated that 1 in 110 children had an autism spectrum disorder, at that time considered a surprisingly high rate.
South Korea doesn’t have an unusually high number of autism cases, says Yale University psychiatrist and study director Young-Shin Kim. Previous studies generated prevalence estimates from medical records of children who had been diagnosed with or showed signs of autism spectrum disorders. Her investigation, published online May 9 in the American Journal of Psychiatry, screened a representative sample of more than 23,000 South Korean 7- to 12-year-olds regardless of whether they had any record of symptoms.
“It seems that many children with autism spectrum disorders have been here all along but haven’t been counted in previous studies,” Kim says.
Prevalence estimates for any ailment based on population surveys are higher and more accurate than those based on data from people already known to have relevant symptoms, says anthropologist and study coauthor Richard Grinker of George Washington University in Washington, D.C.
About two-thirds of South Korean kids diagnosed with an autism spectrum disorder attended public schools where their condition had gone unrecognized and untreated in highly structured classrooms, Kim’s team concludes. Most of these children experienced disorders such as Asperger syndrome (SN: 8/12/06, p. 106) that primarily involve social difficulties. Boys received these diagnoses more than twice as often as girls. All kids with these conditions displayed social impairments severe enough to merit some type of intervention, adds Kim.
Autism, which includes social, intellectual and behavior problems, was the most common diagnosis among South Korean children in special education classes and with registered disabilities. This condition affected boys five times as often as girls.
Cultural factors, such as South Korean parents and clinicians having especially strict definitions of “normal” child behavior, might have influenced the results, remarks psychologist Catherine Lord, director the University of Michigan Autism & Communication Disorders Center in Ann Arbor. But Grinker says the study design addressed such cultural factors.
“This is a solid study and should motivate much further work,” Lord says.
Kim and her colleagues worked from 2005 to 2009 in the city of Goyang, near Seoul. Most participating children attended public schools and had never received special education or psychological services.
A U.S. population survey of autism spectrum disorders needs to be conducted, comments psychologist Geraldine Dawson, research director of Autism Speaks, a private research and advocacy organization in New York City that partly funded the $750,000 South Korea study. “Until then, we won’t know the true extent of these disorders here."
Y.S. Kim et al. Prevalence of autism spectrum disorders in a total population sample. American Journal of Psychiatry. Published online May 9, 2011. doi:10.1176/appi.ajp.2011.10101532