Gross motor function of children with down syndrome: Creation of motor growth curves

OBJECTIVE: To create gross motor function growth curves for children with Down syndrome (DS) and to estimate the probability that motor functions are achieved by different ages. DESIGN: Nonlinear growth curve analysis by using a 2-parameter (rate, upper limit) model. SETTING: Early intervention programs, schools, and children's homes. PARTICIPANTS: One hundred twenty-one children with DS, ages 1 month to 6 years. MAIN OUTCOME MEASURES: Gross Motor Function Measure (GMFM) and severity of motor impairment. RESULTS: The curves for children with mild (n = 51) and moderate/severe (n = 70) impairment were characterized by a greater increase in GMFM scores during infancy and smaller increases as the children approached the predicted maximum score of 85.9 or 87.9. The estimated probability that a child would roll by 6 months was 51%; sit by 12 months, 78%; crawl by 18 months, 34%; walk by 24 months, 40%; and run, walk up stairs, and jump by 5 years, 45% to 52%. CONCLUSIONS: Children with DS require more time to learn movements as movement complexity increases. Impairment severity affected the rate but not the upper limit of motor function. The results have implications for counseling parents, making decisions about motor interventions, and anticipating the time frame for achievement of motor functions.