Prevalence and correlates of mental retardation among children in Karachi, Pakistan.

This paper reports estimates of the prevalence of mental retardation and associated factors based on a population survey of 2- to 9-year-old children in Greater Karachi, Pakistan. A two-phase survey was implemented during the years 1988-1989. In the first phase, a cluster sample of 6,365 children (5,748 from urban areas and 617 from rural areas) was screened for disabilities using a parental report known as the Ten Questions instrument. In the second phase, all children with positive screening results and a 10% sample of those with negative results were referred for structured medical and psychological assessments. Estimates of the prevalence of mental retardation were 19.0/1,000 children (95% confidence interval (CI) 13.5-24.4) for serious retardation and 65.3/1,000 children (95% CI 48.9-81.8) for mild retardation. Both estimates were considerably higher than respective prevalence estimates obtained in industrialized countries and in selected less developed countries. In this population, lack of maternal education was strongly associated with the prevalence of both serious (odds ratio = 3.26, 95% CI 1.26-8.43) and mild (odds ratio = 3.08, 95% CI 1.85-5.14) retardation. Other factors that were independently associated with mental retardation in Karachi included histories of perinatal difficulties, neonatal infections, postnatal brain infections, and traumatic brain injury, as well as current malnourishment. Further research is needed to assess the contribution of consanguineous marriage, improvements in child survival, and other factors to the unusually high prevalence of mental retardation in this population.