Mild mental retardation in Black and White children in metropolitan Atlanta: A case-control study

Objectives. This study assessed differences in the prevalence of mild mental retardation, defined as an intelligence quotient (IQ) from 50 to 70, between Black and White children. Methods. A case-control study design was used. Ten-year-old children with mental retardation were identified from multiple sources. Information on race, sex, maternal age, birth order, economic status, and maternal education was abstracted from birth certificates of 330 case children and 563 control children (public school students). Results. The crude Black-White odds ratio (OR) was 2.6, but it was reduced to 1.8 after the other five covariates were controlled. The disparity was largest among children whose mental retardation was first diagnosed when they were 8 to 10 years old (adjusted OR = 2.5). We found no significant difference in the occurrence of mild mental retardation between Black and White children diagnosed before and age of 6 years (adjusted OR = 1.2). Black children had a higher prevalence of mild mental retardation within all strata of the other five covariates. Conclusions. Five sociodemographic factors accounted for approximately half of the excess prevalence of mild mental retardation among Black children. Possible reasons for the residual difference are discussed.