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Prevalence and Expression of ASD Among Preschool Age Children in New Jersey: 2010-2014
Autism Spectrum Disorder (ASD) surveillance of 4-year old children by a population-based method may offer an opportunity to observe shifts in ASD prevalence early and provide timely information on progress toward early identification goals.
Objectives:
The objectives were to estimate ASD prevalence and describe the expression of ASD in three complete birth cohorts (birth years: 2006, 2008, 2010) at age four, residing in a well-defined metro region and to describe changes in the distribution or expression of ASD, during the period.
Methods:
Case-specific information was from three cycles of active ASD surveillance, according to the Centers for Disease Control and Prevention (CDC) multiple source ascertainment method, reflecting retrospective review and independent analysis of information contained in health and education records. Surveillance confirmed and described individuals with ASD (age 4 years) from the 2010, 2012 and 2014 cycles of ASD monitoring in Essex and Union counties New Jersey and provided demographic data as well as information on the distribution by sex and race/ethnicity and case characteristics, including level of impairment due to ASD, age at first (professional) evaluation, age of ASD diagnosis, cognitive functioning level as indicated by intelligence quotient (IQ) scores. Confidence intervals were based on Poisson sampling distribution. Group differences were compared by Pearson Chi-Square and Fisher’s Exact Tests.
Results:
One thousand, two hundred and seventy four year-old children with ASD were identified in the two county New Jersey surveillance region. ASD prevalence was 19.7 per 1000 (95% CI 17.7, 21.9) in 2010, 22.0 per 1000 (95%CI 19.9, 24.2) in 2012, and 28.3 per 1000 (95%CI 25.9,30.9) in 2014, reflecting a 44% increase. Males with ASD outnumbered females 4:1 but ASD prevalence estimates for white, black and Hispanic children were similar. Intellectual Disability (ID) was identified in a significant but consistent portion of ASD preschoolers (37-41%). Thirty-five to forty percent of surveillance determined ASD cases had an ASD diagnosis by a community provider. Over the four-year period, an increasing proportion of children received an autism test (2010 = 28%, 2012 = 39%, 2014=38%; p<.01). The proportion of ASD children with severe impairment increased (2010 = 19%, 2012 = 20%, 2014 = 23%; p<.001). The proportions of ASD children receiving their first professional evaluation by 24 months and 36 months decreased significantly between 2010 and 2014 (p<0.001).
Conclusions:
Our findings show a 43% increase in ASD prevalence in a young cohort (4 year-olds) from 2010-2014. During this period and in the same region, ASD prevalence increased by 26% in an older cohort (8 year-olds) of individuals, suggesting that ASD prevalence has not peaked and that future peak ASD estimates will be higher. Unexpectedly, our findings disclose that the age of first evaluation is increasing and that fewer ASD children are receiving evaluations by 24 and 36 months.