Association between intellectual functioning and age in children and young adults with Duchenne muscular dystrophy: further results from a meta-analysis.

This study used meta-analytical techniques to explore the association between intelligence and age in children with Duchenne muscular dystrophy (DMD). The sample comprised 1224 children and young adults with DMD (mean age 12 y 3 mo, SD 4 y; range 2 y to 27 y). Standardized measures including the Wechsler Intelligence Scales (WIS) and the Stanford-Binet Intelligence Scales were used to estimate intelligence. No age-related difference was noted for Full-scale and Performance intelligence quotients (IQ). However, Verbal IQ increased significantly with age. Age-related increases were noted for the WIS Information, Similarities, Arithmetic, Comprehension, Digit Span, Picture Arrangement, Block Design, and Coding subscales. These results support the notion that younger children with DMD have deficits in verbal reasoning and verbal processing. Older children with DMD, particularly those of 14 years and older, were less likely to present with these problems. Implications of these findings and possible future research directions are discussed.