Dyslexia More Common in Boys

Nov. 14 -- Most people are very careful to avoid preferential treatment for students based on gender, but new research suggests boys may need special attention to cope with a higher prevalence of reading disabilities.

The findings, which appear in today's issue of the Mayo Clinic Proceedings, are part of a large study that examined the reading skills of 5,718 children born in Rochester, Minn., between 1976 and 1982 who remained in the area after the age of 5.

The researchers found that boys were two to three times more likely to suffer from dyslexia than girls. Dyslexia is a learning disorder in which an individual has difficulty reading despite having had adequate access to education and sufficient intelligence.

Overall incidence of reading disability varied between 5 percent and 12 percent in the study population, suggesting that dyslexia is common in children.

Results of a previous study conducted in Connecticut had established that there were no such gender differences in incidence of dyslexia.

Biological Basis

"There are over 20 million children in the United States between the ages of 5 and 9 and as many as 1 to 2.4 million of them could have dyslexia," says Dr. Slavica Katusic, an epidemiologist at the Mayo Clinic and lead author of today's study.

While all of the contributing factors of dyslexia are unknown, there is strong scientific evidence to suggest that it is genetic in origin.

"There is a difference, literally, in the brain architecture that causes a certain part of the brain of a person with dyslexia to have trouble decoding the written word," says J. Thomas Viall, executive director for the Baltimore, Md.-based International Dyslexia Association.

According to Katusic, previous studies show that male and female brains process reading differently and that these differences may account for the results of the current study.

Katusic plans further research to determine what accounts for these differences. For example, are there risk factors during pregnancy, delivery or after delivery that may contribute to the risk of developing dyslexia.