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.