Autism may be significantly more common than previously thought, researchers said Monday.

In a unique study of 55,000 children in a South Korean town, researchers from George Washington University and Yale found that 1 in 38 had autism.

That rate is nearly three times as high as the most recent prevalence estimates in the United States, which show that the developmental disorder affects 1 in 110 kids.

The finding is significant because the study looked at every child ages 7 to 12 in one particular community. Previous efforts to determine autism prevalence from the Centers for Disease Control and Prevention and other agencies have relied on existing medical or educational records.

“While this study does not suggest that Korean children have more autism than other populations… it does suggest that autism may be more common than previously thought,” said Roy Richard Grinker of George Washington University who worked on the study, which was published online Monday in the American Journal of Psychiatry. “This research powerfully demonstrates that the methods one uses to study prevalence will profoundly influence the estimate.”

For the study, Grinker and his colleagues looked at both children who were and were not enrolled in special education. Parents and teachers were surveyed and the kids underwent diagnostic assessments to determine who had autism.

Ultimately, some children were identified who would have been missed in traditional prevalence studies — including those conducted by the CDC — that rely on existing records, researchers said.