Study Challenges 'All or Nothing' View of Dyslexia
A new study of Connecticut schoolchildren challenges the traditional view of dyslexia as a permanent disability that is easily distinguishable from other kinds of reading problems children encounter in their elementary-school years.
Rather, researchers at the Yale University School of Medicine have concluded, the disability, like hypertension or obesity, varies in severity.
Children considered to be dyslexic in the fist grade may no longer fit the same classification two years later, they said. Conversely, children who are not seen as dyslexia early on may qualify for special help in reading as they grow older.
"it does seem dyslexia is not an all-or-nothing phenomenon," said Robert Makuch, an associate professor of public health at Yale University School of Medicine and one of the study's authors. "What this also implies is that children need constant monitoring as they progress through grade school."
The World Federation of Neurology defines dyslexia as a disorder "manifested by difficulty in learning to read despite conventional instruction, adequate intelligence, and socio-cultural opportunity."
Children with the disorder sometimes transpose letters or have difficulty matching sounds to the letters or groupings of letters they see on a page.
The disability affects an estimated 10 percent of all schoolchildren, and, in recent years, it has been assumed to have a biological basis.
In the study, published Jan. 16 in the New England Journal of Medicine, the researchers described their effort to track 414 randomly selected Connecticut children from when they entered kindergarten in 1983.
The children were given standardized reading tests every year and standard I.Q. tests every two years. For the study, as well as in practice, children defined as dyslexic are those with a marked discrepancy between their intelligence levels and reading abilities.
The traditional view of the disorder holds that such children show up in unexpectedly large numbers-forming a kind of statistical "hump"--at the lower end on scales measuring children's reading ability.
This belief has contributed to the view of dyslexic children as distinct from youngsters who are simply poor readers, and it has also led researchers to look for biological origins to the disorder. "It became very clear where to put the cut point" for classifying children with the disorder, Mr. Makuch explained. "Therefore, it was a distinct entity."
The Yale researchers found, however, that test scores of dyslexic children in their sample fell along a much more normal distribution along the lower end of a standard bell curve.
They said the findings "suggest that dyslexia occurs along a continuum that blends imperceptibly with normal reading ability."
"No distinct cutoff point exists to distinguish children with dyslexia clearly from children with normal reading ability," the report states.
The researchers identified 25 children in the 1st grade, and 31 children in the 3rd grade, as dyslexic. Only 7 children, however--28 percent of the dyslexic 1st graders--fell into that category in both grades. Similarly, only 17 percent of the 1st graders originally diagnosed as dyslexic were still classified that way in the 6th grade.
"Children move in and out in their reading ability, especially in the early years," said Dr. Sally E. Shaywitz, the director of the study and a professor of pediatrics at Yale University School of Medicine. "if we want to identify those who are our most [severely disabled] readers later on, we have to identify a larger group of children as being vulnerable early."
"It would make much more sense to consider younger children at risk for dyslexia rather than to put on unalterable labels," she said.
The researchers said the findings also indicate that methods currently used to classify dyslexic children for special education may be arbitrary.
"Although limitations on resources may necessitate the imposition of cutoff points for the provision of services, physicians must recognize that such cutoffs may have no biologic validity,'' the report concludes. 'A Real Disorder'
The researchers said the findings also mean that educators and clinicians using specific interventions to treat dyslexia might not be able to consider every child who moves out of the disability category a testimony to the success of their methods.
The reason for that, they point out, is that two-thirds of the children in the study shed the label after the 1st grade with no interventions at all.
In an editorial accompanying the study, Dr. Peter B. Rosenberger, the director of the learning-disorders unit at Massachusetts General Hospital, wrote that the findings also raise questions about the way the disability is defined.
"It may be that we want to define it as an aptitude--or talent--deficit rather than a discrepancy between intelligence and reading ability," he added in an interview. "It means it's possible to be dyslexic and still be reading at grade level."
"That's important because such kids are still at risk for problems," he said.
The researchers said the study does not, however, refute the notion that the disability may have biological origins.
They noted, for example, that mental retardation--a disability with much more distinct physiological causes--also occurs within a range of I.Q. scores in any given population.
Dyslexia is "a real disorder," Dr. Shaywitz said. "It's the same kind of variability you have with hypertension and other biological functions."
The study was funded by the National Institute of Child Health and Human Development.