Context: Infants and toddlers with Prader-Willi syndrome (PWS) have mental and motor developmental delay. Short-term data suggest a positive effect of GH on mental and motor development in infants and children with PWS. There are, however, no longer-term results about the effects of GH treatment on mental and motor development.
Objective: To investigate the longer-term effects of GH on psychomotor development in infants and toddlers with PWS and the effect of age at start of GH treatment on psychomotor development.
Design: Prospective cohort study during 3 years of GH treatment.
Setting: The PWS Reference Center in the Netherlands.
Intervention: All children were treated with GH 1 mg/m2/d (≈0.035 mg/kg/d).
Main outcome measures: Mental and motor developmental age assessed with Bayleys Scales of Infant Development II and expressed as percentage of the expected development (100%).
Results: During 3 years of GH, mean (SEM) mental development increased from 58.1% (2.8) at baseline to 79.6% (3.7), and motor development increased from 41.9% (2.9) to 78.2% (3.9; both P < 0.01). A lower baseline psychomotor development and a younger age at start of GH treatment were associated with a higher increase in mental and motor development (P < 0.01).
Conclusions: Mental and motor development increased significantly during 3 years of GH treatment, reducing the gap between infants with PWS and healthy peers. A younger age at start of GH treatment leads to greater improvement in psychomotor development.