The World Federation of Neurology defines dyslexia as a disorder “manifested by difficulty in learning to read despite conventional instruction, adequate intelligence, and sociocultural opportunity.’'
The disability affects an estimated 10 percent of all school- children. Those plagued sometimes transpose letters or have difficulty matching sounds to the letters or groupings of letters they see on a page.
Traditionally, dyslexia has been seen as a permanent disorder that is easily distinguishable from other kinds of reading problems children encounter in their elementary school years. But a new study of Connecticut schoolchildren conducted by researchers at the Yale University School of Medicine challenges this view.
The study concludes that dyslexia, like hypertension or obesity, varies in severity. Children considered to be dyslexic in the 1st grade may no longer fit the same classification two years later. Conversely, children who are not seen as dyslexic early on may qualify for special help in reading as they grow older.
“It does seem dyslexia is not an all-or-nothing phenomenon,’' says Robert Makuch, an associate professor of public health at Yale’s 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.’'
In the study, published in January in the New England Journal of Medicine, the researchers describe 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 IQ 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 that dyslexic children are distinct from youngsters who are simply poor readers; it has also led researchers to look for biological origins to the disorder.
The Yale researchers found, however, that test scores of dyslexic children in their sample fell in a much more normal distribution along the lower end of a standard bell curve. They say 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,’' says Sally 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.’'
And she adds, “It would make much more sense to consider younger children at risk for dyslexia rather than to put on unalterable labels.’'
The researchers say 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.
The researchers say 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, Peter 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 adds in an interview. “It means it’s possible to be dyslexic and still be reading at grade level.’'
“That’s important,’' he says, “because such kids are still at risk for problems.’'
