Objective: Autism occurs more frequently in individuals with Down syndrome than it does in the general population. Among children with autism and Down syndrome, regression is reported to occur in up to 50%. The aim of this study was to characterize and compare regression in children with autism with and without Down syndrome.
Methods: In this case-control study, children with Down syndrome and autism characterized by a history of developmental regression (n = 12) were compared to children with autism with regression who did not have Down syndrome, matched for chronologic age and gender. Comparisons were made on age at acquisition of language and age at loss of language and other skills as measured by the Autism Diagnostic Interview–Revised (ADI-R).
Results: The mean age at acquisition of meaningful use of single words was 40.6 months (SD = 38.0) in children with Down syndrome and autism compared to 14.9 months (SD = 8.5) in children with autism without Down syndrome (p = .005). The mean age at language loss in children with autism with Down syndrome was 61.8 months (SD = 22.9) compared to 19.7 months (SD = 5.8) for those with autism without Down syndrome (p = .01). The mean age at other skill loss was 46.2 months (SD = 19.1) and 19.5 months (SD = 5.6), respectively (p = .006).
Conclusions: When regression occurs in children with autism and Down syndrome it is, on average, much later than is typically seen in children with autism without Down syndrome.