A comparison of characteristics, developmental disorders and motor progression between children with and without developmental coordination disorder

Background and aim: Children with Developmental Coordination Disorder (DCD) have difficulty in the development of motor coordination and with learning new motor skills. Studies demonstrate that children with DCD differ in terms of the nature and severity of their motor difficulties, the incidence of co occurring conditions and family background. However, little is known whether these profiles may relate to motor progression over time. The aim of this study was to describe the profiles of children with and without DCD and track motor progression over time. Method: The characteristics of thirty-four 7-14 year old children (M = 10.07, 85.3% boys) with and without DCD were compared and their motor progression monitored over a two academic years. DCD was identified using DSM5 criteria. The Movement Assessment Battery for Children-2 (MABC-2) was used to classify children as TD (>= 25th percentile), having moderate motor coordination difficulties (6-16th percentile) or severe motor coordination difficulties (<= 5th percentile). The Kaufman Brief Intelligence Test - 2 (KBIT-2) was used to measure full scale IQ. Parent questionnaires were used to gather information on socio economic status and co occurrence of other developmental disorders. We used ANOVA to assess whether there were differences in characteristics between the TD children, children with severe motor coordination difficulties and children with moderate motor coordination difficulties. Linear mixed effect modelling was used to estimate any change in motor performance over time and whether this differed between the three groups of children. Results: Children with severe motor coordination difficulties had distinct profiles in motor and non-motor domains, lower IQ and a greater likelihood of having associated characteristics of 2 or more developmental disorders. We found significant differences between the poor motor performance of the severe group compared to the other two groups. Longitudinal analyses revealed stable, persistent and lower motor competence for the severe group. The rate of change in motor proficiency for the typical and severe groups was similar. However, the group with moderate motor difficulties gained on average more points per week compared to the typical group and achieved motor scores in the typically developing range over time. Conclusions: This is one of the first studies to compare the characteristics and rate of motor progression of children with and without DCD using different motor proficiency cut off scores. The children with severe motor coordination difficulties progressed at the same rate as typically developing peers but remained in the severe group over time, whereas the children with moderate motor coordination difficulties caught up to TDC. The results indicate that different intervention may be required according to the nature and severity of the characteristics in both the motor and non-motor domains of children with DCD.