Poster #43 - Genetic Influences on Co-occurrence and Transmission of Language Impairment and Reading Disability: Extended Pedigree Analysis

• In Event: 3-206 - Poster Session 13
  In Poster Session: PS 13 Section - Developmental Disabilities

Integrative Statement

Individuals with language impairment (LI) experience limitations in language ability that are not attributable to other known factors or medical conditions. Additionally, reading disabilities (RD) are more likely to emerge in children with LI at the onset of academic instruction. Language and reading deficits aggregate in families, though it is still unknown exactly which genes affect these skills and how delays are transmitted. The present study examined how particular characteristics of the language impairment phenotype relate to reading ability within affected individuals and across family generations. Specifically, we utilized an extended pedigree analysis to investigate genetic contributions to the heterogeneity of LI and the heritable phenotypic associations between language impairments and reading disabilities.
The sample included children selected for risk of LI and their nuclear and extended relatives (n=31 probands; N=254 participants). Multigenerational pedigrees were constructed for eligible families and participants were administered standardized measures during in-home visits. The Clinical Evaluation of Language Fundamentals-Fourth Edition (Semel, Wiig, & Secord, 2003) generated index scores for language ability. The Woodcock Reading Mastery (Woodcock, 1987) subtests of Passage Comprehension (short passage reading), Word Attack (non-word decoding), and Word Identification (single word reading) represented literacy skill. Participants were categorized as impaired if they scored at least one standard deviation below the mean on any subtest. Data were analyzed by: diagnostic classification (LI, RD, or co-occurring disorders); language impairment subtype (Receptive-LI, Expressive-LI, or Mixed-LI); and language impairment severity (mild, moderate, or severe).
Within our sample, 18% met diagnostic criteria for LI, 6% met criteria for RD, and 23% met criteria for both disorders. The co-occurrence of LI and RD across families of children selected for LI, along with these impairments co-occurring in one member more frequently than they present separately, demonstrates an increased likelihood for affected individuals to have relatives with similar delays. Also notably, participants with Mixed-LI scored significantly lower on reading subtests, suggesting that concurrent and severe language impairments amplify the risk for developing associated literacy difficulties. Sample-based heritabilities were also computed to decompose the variance in individual differences into genetic and environmental influences. All univariate heritability estimates of the language and reading constructs were significant, h2=.38-.96 (Table 1). Further, bivariate heritability estimates showed that all language and reading impairments were significantly phenotypically (rp=.50-.99) and genetically (rg=.75-.99) correlated (Table 2).
Current findings corroborate past studies documenting the relation between language and reading disorder, as well as the high heritability of comorbidity. Our ongoing molecular genetics research combines with present quantitative results to investigate specific modes of familial transmission (e.g., between particular relative dyads), and the genetic variants implicated in their etiology, in order to better define language and reading disorder. These data point to the co-inheritance of LI and RD, providing evidence of a broader phenotype in family liability of developing these deficits. This shared biological influence can inform treatment such that the type of impairments discovered throughout extended generations may hint at the prognosis of the development of younger generations, creating opportunities for earlier implementation of targeted interventions and focus for prevention.

Authors

• Laura L. Mason, The Ohio State University
  Presenting Author

• Christopher W. Bartlett, The Ohio State University
  Non-Presenting Author

• Stephen Petrill, The Ohio State University
  Non-Presenting Author