Longitudinal changes in cognitive and adaptive behavior in fragile X females: A prospective multicenter analysis

In prospective studies of young, fragile X [fra(X)] males with the full mutation, cognitive abilities (IQ scores) and adaptive behavior levels (DQ scores) declined in most subjects tested. Little is known about longitudinal changes in IQ and DQ scores in young fra(X) females, although one earlier retrospective study showed declines in IQ scores in 8 of 11 subjects. To examine fra(X) females prospectively, we tested and retested 13 females with the full mutation, age 4 to 15 years. Nine were tested and retested in North America, and four were evaluated at the Catholic University in Leuven, Belgium. Cognitive abilities of North American females were measured using the Stanford-Binet 4th Edition. Adaptive behavior levels were ascertained from the Vineland Adaptive Behavior Scales. For Belgians, test-retest scores from the Wechsler Intelligence Scales for Children—Revised were used. Subjects were subsequently separated into two age cohorts: those tested initially before age 7 years and those tested initially after age 7 years. Compared with young males with the full mutation and of the same age, females expectedly display a wider range of IQ scores. Test-retest IQ scores showed statistically significant decreases (P IQ. Am. J. Med. Genet. 83:308–312, 1999. © 1999 Wiley-Liss, Inc.