The objective of the study was to report the incidence of reading disability among school-aged children. Overall, the incidence of reading disability was 5.3 percent to 11.8 percent depending on the definition used to establish it. (Incidence, a measure of singular importance in epidemiology, is primarily used to estimate the risk individuals have of acquiring a particular condition.)
The study's results and an editorial on the topic appear in the November issue of Mayo Clinic Proceedings. "Our study provides a powerful opportunity to learn more about reading disability," says Slavica K. Katusic, M.D., a Mayo Clinic epidemiologist and the primary author of the study. "These data demonstrate that reading disability is common among children and should be included among the differential diagnoses considered in children having problems with learning. Moreover, these data suggest that this diagnosis should be given a higher prior probability in boys than in girls."
The majority -- approximately 80 percent -- of children identified as having learning disabilities have their primary academic problem in reading. The World Federation of Neurology defines reading disability as a disorder manifested by difficulty in learning to read despite conventional instruction, adequate intelligence and sociocultural opportunity.
The study's report is from an ongoing epidemiologic study of learning disability among all children born from 1976 through 1982 in Rochester, Minn. An interdisciplinary team of investigators used comprehensive, medical, educational and tutorial resources available on all 5,718 children.
Currently, there are no universally accepted tests, assessment batteries or standards for identifying children with learning disability. The Mayo researchers report that they employed the most widely used approaches to determine eligibility for reading disability intervention.
In an editorial in the same issue of Mayo Clinic Proceedings, Drake D. Duane, M.D., of the Institute for Developmental Behavioral Neurology in Scottsdale, Ariz., says the Mayo Clinic data have implications for shaping public policy.
"For society and its educational systems, the question of the incidence of learning disorders is crucial if the academic outcome for each learner is to be optimized," writes Dr. Duane. "What are the characteristics of the students who require altered educational instruction, what specific alterations must that instruction entail, and when and for how long should it be delivered?"
He notes that the Mayo Clinic researchers point out that the Minnesota data does not overestimate the incidence of reading disability; they are probably close to quantifying the actual occurrence, Dr. Duane writes.
"This report from an academic medical center powerfully demonstrates the utility of interdisciplinary investigation in matters of education that may help shape appropriate public policy," Dr. Duane concludes his editorial.
Mayo Clinic Proceedings is a peer-reviewed and indexed general internal medicine journal, published for 75 years by Mayo Foundation, with a circulation of 130,000 nationally and internationally.