17971
Prevalence Changes in Autism Spectrum Disorders over an 8-Year Period in South Carolina
There has been growing awareness of autism spectrum disorders (ASD) as a significant public health concern. Once thought of as a rare developmental disability, service providers report continued increases in ASD. Congress passed legislation in 2000 to provide funding for the Centers for Disease Control and Prevention to establish a network of sites in the United States to report the prevalence of ASD. These sites are called the Autism and Developmental Disabilities Monitoring Network (ADDM). The Medical University of South Carolina (SC ADDM) has been a member of the ADDM network since 2000.
Objectives:
1. To examine changes in ASD prevalence over an 8-year period in South Carolina, a state with significant racial and economic diversity. 2. To explore prevalence changes by gender. 3. To investigate changes in age at first diagnosis of ASD including any changes in community reporting.
Methods:
SC ADDM has conducted population-based multiple-source surveillance for ASD using identical study methodology within the same catchment area since 2000. The SC ADDM method uses chart reviews from clinical, education, and disability board records, followed by expert clinician review to determine surveillance case definition. With multiple agreements from SC state agencies, records for children who are 8 years old are screened for behavior triggers and later reviewed by clinical experts to see if that child meets the requirements for an ASD according to the DSM-IV definition.
Results:
In South Carolina, there was a 76% increase in the prevalence of ASD over an 8-year period. In 2000, ASD prevalence was 6.3 / 1000 or 1 in 159 eight year olds. In 2008 ASD prevalence was 11.1/1000 or 1 in 90. Male to female ratio increased 86%, from 2.8 to 1 to 5.2 to 1. The largest increase in ASD prevalence was in males from 9.3/1000 to 19.5/1000. Girls stayed approximately the same, 3.3 to 4.0 / 1000. The median age of first diagnosis of ASD found in any record was 54 months in 2000 and again was 54 months in 2008. In 2000, ASD was recognized in 35% of all ASD records reviewed. Eight years latter ASD was recognized in 63% of ASD records, indicating an increase in the diagnostic rate in available records.
Conclusions:
SC ADDM found 135 more children in an 8-year time span in exactly the same SC geographical region, using identical methodology in each study year. This is an 87% increase, when the population of 8-year olds actually decreased approximately 7% during this time. The increase in case finding is primarily due to the increased number of identified males. Despite increased emphasis on early detection, the average age of first diagnosis remained 4 years, 6 months across study years, leading to missed opportunities for autism specific early intervention. Despite this, there was a significant increase in the recognition of the characteristics of ASD found in clinical records.