Higher-Order Repetitive Behaviors in Toddlers Born Preterm

Background:  Preterm birth is associated with lower IQ, impaired self-regulation, and social communication deficits. Preterm infants are also more likely to receive psychiatric diagnoses including ASD, the prevalence of which is 7% in children born preterm (as compared to 1.5% in the general population) (Johnson et al., 2010). These findings add to the extant literature suggesting the heterogeneous etiology of ASD, and highlight the need for screening tools that capture the dimensionality and heterogeneity in contributing mechanisms and clinical outcomes of ASD.

Objectives:  The current study uses the Repetitive Behavior Scale for Early Childhood (RBS-EC; Wolff, Boyd, & Elison, 2016) to compare restricted and repetitive behaviors (RRBs) in preterm (36 weeks gestational age or earlier) and full term toddlers in a community sample of 1,670 participants.

Methods:  Parents of toddlers between 17 and 23 months of age were recruited from the Institute of Child Development participant pool registry. Parents were asked to fill out the RBS-EC, an instrument designed to characterize dimensional aspects of RRBs in young children. Of the 1,955 parents who completed the RBS-EC, 285 were excluded for providing responses that suggested invalid data (e.g. time to complete survey was less than 3 minutes) or for missing gestational age data.

Results:  Data from 1,670 participants were analyzed. Of these participants, 5.9% were born preterm (n=99). The average age at assessment did not significantly differ between groups (Preterm Infants’ Mean Age=20.6 months, Fullterm Infants’ Mean Age=20.1 months). Overall, parents of preterm toddlers endorsed a greater number of behaviors (t(1666)=2.7, p=.007) and reported a higher frequency of these behaviors (t(1666)=1.9, p=.05). Analyses of the subscales on the RBS-EC indicated no group differences in Self-directed or Repetitive Motor topographies. Group differences emerged in Restricted and Ritual topographies, with parents of preterm toddlers endorsing more items and reporting higher frequencies of these behaviors (Table 1). Birthweight, Gestational Age, and Age at Assessment were then entered in a multiple linear regression model. Birthweight significantly predicted the number of Restricted Behaviors Endorsed (t(1666)=-3.3, p=.001), the frequency of Restricted Behaviors (t(1666)=-2.9, p=.003), and the frequency of Ritual and Routine Behaviors (t(1666)=-2.5, p=.01) after controlling for Gestational Age and Age at Assessment. The effect of Birthweight on the number of Ritual and Routine Behaviors endorsed trended towards significance (t(1,666)=-1.7, p=.089).

Conclusions:  RBS-EC measures collected from a large community-based sample (n=1,670) indicate that infants born preterm do demonstrate a greater degree of higher-order RRBs as toddlers, as indexed by both topographies endorsed and frequency of these behaviors. Future analyses will expand on these findings by using continuous measures of Age and Gestational Age to better understand the effect of preterm birth on RRBs. Furthermore, data collected on a social-responsiveness measure – the vrRSB – in the same cohort will be analyzed to determine whether these effects are specific to RRBs, or to features of ASD more generally. These data add to the growing body of evidence demonstrating that preterm birth is a risk factor for ASD by identifying elevated RRBs during the second year of life.