Longitudinal trajectories and reference centiles for the impact of health conditions on daily activities of children with cerebral palsy

AIM: First, to describe the impact of health conditions on daily activities over time in children with cerebral palsy (CP) and to create age-specific reference centiles. Second, to determine the amount of change typical over a 1-year period, across Gross Motor Function Classification System (GMFCS) levels. METHOD: A prospective, cohort design, with five assessments over 2 years, involved 708 children with a confirmed diagnosis of CP participating in the On Track Study (396 males, 312 females; mean age 6y [SD 2y 7mo]; range 18mo-12y at first assessment; 32.1% in GMFCS level I, 22.7% in GMFCS level II, 11.2% in GMFCS level III, 18.2% in GMFCS level IV, 15.7% in GMFCS level V). The impact of health conditions on daily activities was assessed using the Child Health Conditions Questionnaire. Data were analyzed using mixed-effects models and quantile regression. RESULTS: Linear longitudinal trajectories describe the relatively stable impact of health conditions over time for each functional level for children aged 2 years to 12 years, with the lowest scores (least impact) in GMFCS level I and the highest scores (highest impact) in GMFCS level V. Centiles were created for children in each GMFCS level. A system to interpret the magnitude of change over time in centiles was developed. INTERPRETATION: Longitudinal trajectories of co-occurring health conditions assist with understanding children's prognoses. Centiles assist in understanding a child's experience relative to children in similar GMFCS levels. Guidelines are provided to determine if children are progressing 'as expected', 'better than expected' or 'more poorly than expected' in regard to the impact of health conditions on daily activities. WHAT THIS PAPER ADDS: For children with cerebral palsy, the mean impact of health conditions on daily activities is relatively stable. Significant intraindividual and interindividual variability for the impact of health conditions exists, which complicates prognosis. Centiles enable interpretation of the impact of health conditions relative to Gross Motor Function Classification System level.