Background: Reading disabilities (RD) are the most common learning disabilities, affecting 3-7% of school-aged children in North America. RD is associated with increased risk for comorbid language-based disorders including early language delay (ELD), speech sound disorders, and language impairments. Despite decades of research on the relationship between RD and these disorders, questions remain as to the strength of their associations. This study is the first of this size to assess all four disorders in a sample of children with RD. Method: We examined the association these disorders in a large, well-characterized family-based sample, recruited for reading difficulties in school-aged children. Parents of 492 families (674 children) completed a questionnaire that queried ELD, and current speech and language difficulties in their children. Children were also directly assessed for multiple quantitative measures of language and reading. Children were divided into three groups: Reading Disabled (RD), Intermediate Readers (IR), and Typical Readers (TR). Results: We found that the parents of the RD and IR groups reported significantly more ELD and current speech and expressive/receptive language difficulties in their children, compared with the TR group. When examined further, we found ELD was associated with poorer performance on word reading and decoding tasks, as well as with speech and language difficulties. Conclusion: The results demonstrate multiple significant associations between reading difficulties, ELD, speech and language, especially in children with severe RD. The results add to research supporting comorbidity between these disorders and will help inform teachers and psychologists when assessing and treating children’s language-based disabilities.
