Cognitive functioning in children with Prader-Willi syndrome during 8 years of growth hormone treatment.

Objective: Children with Prader-Willi syndrome (PWS) have mild to moderate cognitive impairment. Short-term studies showed positive effects of growth hormone (GH) on cognitive development. This study investigated the effects of 8 years of GH on cognitive development in children with PWS. We also investigated whether starting GH during infancy results in higher cognitive functioning after 8 years of GH. Design: Longitudinal study in 43 children with PWS during 8 years of GH (median age at GH start 8.1 years). Cognitive functioning after 8 years was compared to another group of 22 children with PWS (median age at GH start 1.4 years). Methods: Cognitive functioning was measured by Wechsler Intelligence Scale for Children. Vocabulary, Similarities and Block Design subtests were expressed as standard deviation scores (SDS) and total IQ (TIQ) calculated. Results: Estimated mean (95%CI) Block Design SDS changed from -2.2 (-2.6; -1.8) at GH start to -1.8 (-2.2; -1.4) after 8 years of GH (P = 0.18), similarly SDS from -1.5 (-2.1; -0.9) to -1.3 (-1.9; -0.7, P = 0.66) and TIQ from 66 (60; 72) to 69 (63; 75, P = 0.57). Vocabulary SDS remained similar, being -1.9 (-2.3; -1.4) at GH start and -1.9 (-2.4; -1.5) after 8 years (P = 0.85). After 8 years of GH Vocabulary, SDS and TIQ were higher in the children who started GH during infancy, compared to those who started GH later in childhood (P < 0.01, P = 0.04, respectively). Conclusions: Cognitive functioning in children with PWS remains similar during long-term GH and develops at the same pace as healthy peers.