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Krista A. Schwenk1,2,
Jennifer Miller2, John H. Kranzler1, Christy H. Lynn2,
Daniel J. Driscoll2
College of Education1 and Department of Pediatrics2,
University of Florida, Gainesville
Introduction:
Decreased cognitive abilities are one of the defining characteristics of PWS.
However, a wide range of IQ scores (12 to 100) have been reported by a number of
groups. Some of the reasons for this broad range of scores have been thought to
be due to differences in molecular class, as well as deletion size (Butler et
al., 2004). It has also been postulated that growth hormone therapy may have an
effect on cognition. Furthermore, many years ago, Crnic and colleagues (1980)
found a significant difference in IQ in individuals who became obese at an early
age versus those who did not, but this study has not been replicated. The
purpose of the current study is to further explore factors that may have an
impact on the broad range of cognitive scores in PWS.
Methods:
The Woodcock-Johnson Tests of Cognitive Abilities, Third Edition (WJIII-Cog)
and the Woodcock-Johnson Tests of Achievement, Third Edition (WJIII-TA) were
used to determine the cognitive and achievement abilities of 26 individuals with
PWS who were greater than or equal to six years of age, as well as their normal
sibling control participants. The WJIII Tests of Cognitive Abilities (WJIII-Cog)
was developed to assess general intelligence as well as the broad cognitive
abilities of the Cattell-Horn-Carroll (CHC) theory of individuals between 2 and
90+ years of age. The WJIII tests of cognitive abilities and achievement were
co-normed on a large, nationally representative sample. Extensive genetic
testing was conducted on the PWS participants.
Results:
The average IQ of the individuals with PWS was a standard score of 66 and ranged
from 35 to 106, while the average IQ of the sibling controls (N = 12) was
107 with a range from 99 to 116. The average overall achievement score (TIA) of
the individuals with PWS was a standard score of 70 and ranged from 21 to 123,
while the average TIA of the sibling controls was 106 and ranged from 89 to 118.
In terms of molecular class within PWS, the average IQ of the individuals with a
deletion (N = 16) was 67 and ranged from 35 to 106, while the average IQ
of the individuals with uniparental disomy or imprinting defect (N = 10)
was 64 and ranged from 38 to 103. The average TIA of the individuals with a
deletion was 70 and ranged from 21 to 93, while the average TIA of the
individuals with uniparental disomy/imprinting defect was 69 and ranged from 21
to 123.
Discussion:
Similar to the findings of other studies, we also found a wide range of
cognitive and achievement scores among the individuals with PWS in our study. We
are currently exploring various factors to try and understand which variables
may impact positively and which negatively on an individual’s IQ. Some of the
factors being explored include age of onset of obesity; early nutritional
history; socioeconomic status; siblings IQ; age of diagnosis; receipt of
services (e.g., special education, tutoring, speech/language therapy, physical
therapy, occupational therapy, and parental involvement), as well as early
treatment with medications, such as growth hormone, CoQ10, carnitine, and fish
oil.
Edited:
02/09/2012
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