Background

Autism spectrum disorder (ASD) is a neurodevelopmental disability characterized by deficits in social interaction and communication, and the presence of repetitive and restricted behaviors/ interests (RRBs) that can cause major problems in social

interaction and communication (American Psychiatric Association, 2013). Individuals with ASD were previously given a diagnosis of Autistic disorder, Pervasive

developmental disorder—not otherwise specified (PDD-NOS), or Asperger’s disorder according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR). In the fifth edition, all these diagnoses are now subsumed under the single label of ASD. The prevalence of ASD among 8-year-old children in the United States increased from 6.7 per 1,000 children in 2000 to 14.7 per 1,000 in 2012 (Autism and Developmental Disabilities Monitoring Network Surveillance Year 2000 Principal Investigators & Centers for Disease Control and Prevention, 2007; Autism Developmental Disabilities Monitoring Network Surveillance Year 2010 Principal Investigators, 2014). In Taiwan, the cumulative prevalence of ASD among 3- to

17-year-old children increased from 0.18 per 1000 children in 1996 to 2.87 per 1000 in 2005, and the prevalence rate increased rapidly to 2.21% in 2011 (Chien, Lin, Chou, &

Chou, 2011; Hwang, Weng, Cho, & Tsai, 2013; Lai, Tseng, & Guo, 2013). Parents have most frequently expressed concerns regarding the development of their children before the age of 3 years, but diagnoses of ASD occur at ages of approximately 4 – 6 years.

(De Giacomo & Fombonne, 1998; Hwang et al., 2013; Lai et al., 2013). Therefore, early intervention for children with ASD is necessary to address the symptoms of ASD and long-term outcomes.

RRBs are a core feature of ASD that include symptoms of stereotyped or repetitive motor movements, insistence on sameness, and inflexible adherence to routines.

Although RRBs are normally observed in typically developing (TD) toddlers (Morgan, Wetherby, & Barber, 2008), previous studies have indicated that children with ASD demonstrate significantly higher frequencies and longer durations of RRBs than do TD toddlers (Barber, Wetherby, & Chambers, 2012; Fulceri et al., 2016; Kim & Lord, 2010;

Richler, Bishop, Kleinke, & Lord, 2007). Furthermore, the symptoms of RRBs have been associated with more severe ASD symptoms and more impaired motor, language, cognitive, and social interaction functioning among children with ASD (Elison et al., 2014; Kim & Lord, 2010; Morgan et al., 2008; Richler, Huerta, Bishop, & Lord, 2010;

Watt, Wetherby, Barber, & Morgan, 2008). Therefore, assessment of RRBs in the early childhood is important to help identify early symptoms of ASD in young children.

Several clinically oriented measures are used for measuring RRBs in children with ASD. These methods include caregiver interviews, questionnaires, and observational methods. Caregiver interviews, such as the Autism Diagnostic Interview-Revised, include several repetitive behavior items for detecting features of RRBs. Questionnaire measures such as the Repetitive Behavior Scale-Revised (RBS-R) or the Repetitive Behavior Scale for Early Childhood (RBS-EC) are caregiver rating scales also capable of capturing a wider range of behavioral features. However, because interview or questionnaire measures are subjective, their accuracy may be hampered by recall bias.

In addition, semi-structured observational methods, such as the Repetitive and Stereotyped Movement Scales (RSMS) and the Autism Diagnostic Observational Schedule (ADOS), are designed for clinicians to examine the RRBs of children by interacting with children in standardized testing procedures. Although semi-structured observational methods are relatively objective and yield quantitative data, these

methods are more labor intensive and may be constrained by the RRBs observable during the assessment, such as a focus on stereotypical motor movements rather than on restricted rituals or routine behaviors. Cohen et al. (Cohen, Gardner, Karmel, & Kim, 2014) used an automatic behavioral tracking system to investigate behavioral trajectory of children with ASD in free play situations. Several time- and space-related variables relevant to behavior characteristics and interest were analyzed. The results revealed that children with ASD had a longer period of latency to approach parents and more time spent at the periphery than did atypically developing (ATD) children. Furthermore, the time spent at the periphery was positively and moderately correlated with the severity of ASD (r = 0.63). Thus, the automatic behavioral tracking system is a valid method for investigating the characteristics of RRBs in ASD.

Although social communication deficits and abnormal behavioral performance are important diagnostic criteria for ASD, the high co-occurrence of motor deficits

contributes to the clinical features of ASD. Abnormalities in motor-related brain regions and associations with motor impairments were identified in children with ASD. These findings indicated possible common neurological roots that are primarily involved in sensory–motor coordination problems and link to the core symptoms of ASD (Carr, Iacoboni, Dubeau, Mazziotta, & Lenzi, 2003; Courchesne et al., 2011; Courchesne et al., 2007; Oberman et al., 2005; Rizzolatti, 2005; Rizzolatti, Fogassi, & Gallese, 2001). In addition, previous studies have revealed that motor problems, including delayed gross and fine motor development, delayed postural development, and stereotyped

movements, can be observed in toddlers or preschoolers with ASD (Bhat, Galloway, &

Landa, 2012; Gernsbacher, Sauer, Geye, Schweigert, & Hill Goldsmith, 2008; Lloyd, MacDonald, & Lord, 2013; Nickel, Thatcher, Keller, Wozniak, & Iverson, 2013;

Ozonoff et al., 2014). Furthermore, early motor problems have been found to associate

with delayed and impaired social interaction and communication (Bhat et al., 2012) and maladaptive behaviors at older ages (MacDonald, Lord, & Ulrich, 2013). However, previous studies have used parental reports or home videos rather than standardized developmental assessment tools for assessing children’s motor function and were accordingly lacking detailed information regarding motor development in multiple motor dimensions. Moreover, no studies have yet assessed early motor development in Taiwanese children with ASD. A comprehensive evaluation of motor function in Taiwanese toddlers with ASD is warranted.

In addition to understanding the behavioral and motor development in young children with ASD, children born prematurely must be considered for long-term

development because they are more likely to show multiple developmental problems in early childhood and to sustain lifelong consequences. Preterm children are defined as live babies born before 37 weeks of pregnancy. Despite the increase in annual survival rates in preterm infants, a higher diagnostic rate of cerebral palsy, blindness, hearing impairments, intellectual disability, and multiple developmental disorders has been observed in preterm children than in full-term children (Barre, Morgan, Doyle, &

Anderson, 2011; Doyle, 2004; Linsell, Malouf, Morris, Kurinczuk, & Marlow, 2016;

Stoelhorst et al., 2003; Wong, Huertas-Ceballos, Cowan, & Modi, 2014). ASD is one of the neurodevelopmental disorders observed among preterm children, with an estimated prevalence of approximately 5 – 8% in the preterm cohort (Johnson et al., 2010;

Pinto-Martin et al., 2011). Furthermore, prematurity and very low birth weight (VLBW) are considered to be risk factors for ASD (Hwang et al., 2013; Kuzniewicz et al., 2014;

Lampi et al., 2012; Leavey, Zwaigenbaum, Heavner, & Burstyn, 2013; Limperopoulos et al., 2008). More autistic traits and ASD symptoms were detected in the VLBW preterm infants as compared with full-term infants in childhood (Williamson &

Jakobson, 2014a, 2014b; Wong et al., 2014). Previous studies have reported that, in early childhood, a greater number of autistic traits were detected in VLBW preterm infants than in full-term infants, and significantly higher percentages of children showed positive results in the screening of ASD before the age of 3 years (Gray, Edwards, O'Callaghan, & Gibbons, 2015; Guy et al., 2015; Limperopoulos et al., 2008).

In addition to the high prevalence of autistic traits, behavioral problems are commonly observed in VLBW preterm children. Numerous studies have revealed that VLBW preterm children at preschool and school ages manifest adverse behavioral outcomes such as an excess of internalizing and externalizing problems (particularly, problems with attention), withdrawn behavior, poorer adaptive functioning, and lower levels of social and school competence (Gray et al., 2015; Hayes & Sharif, 2009;

Johnson, 2007; Johnson et al., 2010; Johnson & Marlow, 2011; Limperopoulos et al., 2008; Pritchard et al., 2016). In addition to behavioral problems, VLBW preterm children have a high co-occurrence of motor impairment in early childhood. Compared with their term peers, VLBW preterm children tend to exhibit a delayed attainment of motor skills, such as a delayed acquisition of crawling, sitting, and walking (van Haastert, de Vries, Helders, & Jongmans, 2006), muscle imbalance (Pin, Eldridge, &

Galea, 2010); and abnormal gait pattern (Cahill-Rowley & Rose, 2016; Pin et al., 2010), which causes impaired motor function at older ages. Therefore, early identification of motor and behavioral problems to predict later developmental disorders is helpful for early intervention among VLBW preterm children. Although many studies have focused on motor and behavioral developments among VLBW preterm children in the early childhood, no studies have compared the motor and behavioral developments of VLBW preterm children and full-term children with ASD in early childhood. By contrast, several studies have compared young children with ASD and ATD children with

different developmental problems (e.g., global developmental delay or language disorder etc.). Results have indicated that children with ASD revealed more impaired motor functions (Bolton, Golding, Emond, & Steer, 2012; Hellendoorn et al., 2015;

Karmel et al., 2010; Lam & Aman, 2007; Waelvelde, Oostra, Dewitte, Broeck, &

Jongmans, 2010; Zappella et al., 2015) and higher rates of behavioral problems than did ATD children (Elison et al., 2014; Kim & Lord, 2010; Morgan et al., 2008; Richler et al., 2007). Considering the necessity of the early identification of VLBW preterm children who are at risk of developing ASD for early intervention, examining the differences or similarities in motor and behavioral development between VLBW preterm children and full-term children with ASD is important.