Early Developmental Characteristics of Children with ASD in SPARK
The SPARK cohort offers the opportunity to characterize the natural history of autism in a representative cross-sectional sample of unprecedented size.
To describe early development and regression in SPARK participants.
Developmental data including regression and symptom onset were collected through online parent surveys. Variables were harmonized with ASD-UK for future meta-analysis. Participants were 21,254 children aged 15 months to 17 years with a reported professional ASD diagnosis.
The average ages of major motor milestones were 6.7 months for sitting unsupported and 14 months for walking independently. Only 3-6% exhibited severe delays, defined as sitting after 12 months or walking after 2 years. The average age of speaking single words was 20.7 months. Among children over 2 years (n=20,161), the average age of speaking simple phrases was 32.8 months, with 60% achieving phrase speech between two and three years of age.
The average age of parental first concern was 22 months, with language (28%) and social concerns (19%) the most common first signs. Only 9.7% reported that regression signaled onset of ASD symptoms. However, one-third of parents reported a complete loss of speech typically in the second year, at an average age of 22.4 months. Regression usually lasted one to two years, but one-third of cases reported that regression had not yet resolved. 27% experienced a regression in social/play or other skills, but significantly later at an average age of 34.7 months. 56% of parents reported their child’s nonverbal cognitive ability as mildly to significantly delayed. Nonverbal cognitive delay was higher in those who had regression in language (66%) than in those who did not experience regression (50%).
Online parent survey data in SPARK closely mirror findings from developmental studies of confirmed ASD diagnoses. Early gross motor skills are within normal limits. SPARK participants report less severe language delay than previous studies, which may reflect improving sensitivity in detection and diagnosis. ASD symptom onset usually occurs in the first two years, often before regression, and is rarely heralded by repetitive behavior but rather by language concerns. Children with language regression have a greater likelihood of persistent delay in non-verbal cognitive ability, which supports a clinical subtype of ASD. SPARK offers potentially the largest data source of its kind to examine predictors and etiologies in autism, including those specific to autism in the absence of other disability.