LONGITUDINAL CHANGES IN IQ AMONG FRAGILE-X FEMALES - A PRELIMINARY MULTICENTER ANALYSIS

Longitudinal declines in IQ among fragile X [fra(X)] males have been r eported previously by several investigators. Remarkably little is know n about longitudinal changes in IQ scores among fra(X) females. Previo usly, one cross-sectional study showed a significant negative correlat ion between age and IQ scores. However, a recent investigation of girl s with fra(X) syndrome noted longitudinal increases in IQ scores in 8 of 11 individuals. Therefore, the purpose of this preliminary multicen ter study was to determine: (1) the characteristics of longitudinal ch anges in IQ among fra(X) females; and (2) whether these changes were c omparable to those which have been observed among fra(X) males. IQ tes t and retest scores for 11 fra(X) females were obtained from 3 centers : Greenwood, South Carolina; Ibaraki, Japan; and Leuven, Belgium. To e nsure high reliability, only test-retest scores from the Wechsler and Stanford-Binet tests were used. Age of subjects at initial testing ran ged from 5 to 35 years. Mean intertest interval was 4.5 years. In cont rast to a report of longitudinal increases, we Found 9/11 (82%) subjec ts demonstrated decreases in IQ scores. Mean decline was 9 points. Fem ales over 18 years of age showed little or no change in IQ scores. Dec reases in scores appeared to be related to initial IQ score. Females i n the earlier longitudinal report were higher functioning than those i n our study, which may account for the observed difference in directio n of change; or, change in IQ score may be related to size of the fra( X) mutation. These preliminary findings are consistent with our earlie r multicenter study of fra(X) males and suggest that while cognitive d eficits are greater initially among males than females, longitudinal c hanges in IQ scores are comparable. (C) 1994 Wiley-Liss, Inc.