Genetic epidemiology of stuttering among school children in the state of Tamil Nadu, India

Purpose: Stuttering is a fluency disorder with a worldwide prevalence of 1%. Reports on the epidemiology of stuttering in India are limited. Our primary goal was to examine the prevalence of the disorder among school children. The study also aimed to examine risk factors associated with severity and the impact of parental consanguinity in stuttering.

Method: Children from 97 schools in the State of Tamil Nadu, India were screened. Extensive speech characterization, epidemiological details and three-generational pedigrees were collected for 180 probands. The genetic basis of stuttering was examined using the analysis of genealogical index of families (GIF), kinship group and sibling recurrence risk (SRR) measures. Regression analysis and chi-square tests were performed to test the association of risk factors with severity of the disorder.

Results: Among the 74,544 school children screened, the prevalence of stuttering was found to be 0.46%. Pedigree analysis revealed a positive family history in 101 (56%) probands; overall familial incidence was 11%. We observed an overall male-favored sex ratio (4:1). Familial aggregation (GIF = 442.60, p-value <0.001) and sibling recurrence risk ratio (K_s = 0.197, SD = 0.041) was high among consanguineous families. Severity of stuttering was strongly associated with gender and moderately associated with age at onset.

Conclusion: The prevalence of stuttering in Tamil Nadu is estimated for the first time in this study. High familial incidence, familial aggregation and sibling recurrence risk ratio point to the presence of a genetic basis. Familial aggregation was high among consanguineous families although consanguinity did not seem to play a role in severity.