Demographic Profile of Families and Children Enrolled in the Study to Explore Early Development (SEED): A Case-Control Study of Autism Spectrum Disorder

Background:  The Study to Explore Early Development (SEED) was designed to enhance knowledge of autism spectrum disorder (ASD) characteristics and etiologies.  Disparities in ASD prevalence according to race, ethnicity, and socioeconomic status have been reported, which may reflect differences in underlying etiologies or in ascertainment or diagnosis.  SEED presents a unique opportunity to investigate the demographic profile of ASD because of its population-based, multi-site ascertainment and large sample size.  

Objectives:  Our objective was to describe the demographic profile of families and children enrolled in SEED, and compare demographic characteristics among the three study groups: children with ASD, children with developmental delay or disorder (DD) and population controls (POP).

Methods:  Children aged 2-5 years were ascertained through birth certificate records and multiple health and education sources serving children with developmental problems.  The primary caregiver was interviewed to collect demographic characteristics of the household, biological parents, and enrolled child.  Groups were compared using ANOVA or multinomial logistic regression, as appropriate.

Results:  Caregiver interviews were completed for 2,229 children enrolled between December 2007 and May 2011, including 597 ASD, 835 DD, and 797 POP.  Child mean age at enrollment (M=54.9 months, SD=7.7) did not differ by study group.  Overall, 64.8% were male; as expected, child sex differed significantly among the three groups, ranging from 52.8% in POP controls to 79.2% in children with ASD.  Mean maternal and paternal ages at child’s birth were 31.9 years (SD=5.5) and 34.1 years (SD=6.1), respectively.   Maternal race included White (69.0%), Black (15.9%), Asian (5.1%), Multi-Racial (4.5%) and Other Race (5.4%).  Among mothers, 11.9% were Hispanic, 17.8% were foreign born and 10.6% primarily spoke a language other than English.  Mothers were well educated, with 85.4% having had at least some formal education after high school and only 5.3% not having finished high school.   Characteristics of fathers were similar to those of mothers:  17.3% were Black, 4.8% Asian, 3.2% Multi-Racial, and 6.3% Other Race; 12.1% were Hispanic; 18.2% were foreign born; and 76.3% had some formal education after high school.  Total household income in the year prior to the interview was generally high; 28.5% had yearly incomes greater than $110,000 while only 31.8% had incomes of $50,000 (median US household income) or less.  Average household size was 4.3 (SD=1.2).  There were significant differences among the three study groups in household income and in maternal and paternal race, ethnicity, country of birth, primary language, and education.  There were no group differences for maternal or paternal age or household size.

Conclusions:  SEED successfully enrolled a diverse sample of participants, including substantial proportions of minority and immigrant families.  Although the sample was generally high income and well educated, socioeconomic differences among the three study groups were nevertheless identified, as were other demographic differences by group.  SEED offers important opportunities to explore sociodemographic risk factors related to ASD.