The aim of this study was to find the prevalence of mild mental retardation (MMR) in 6-10-y-old children in a prospectively followed cohort in Pakistan from four areas with different socioeconomic conditions. Retarded children were identified by a two-step method, comprising a household screening with the Ten Questions Screening in 649 families followed by clinical investigation and psychometric testing (WISC-R and Griffiths) of the 132 children found by the screening. The overall prevalence of MMR among 6-10-y-old children was 6.2%. The distribution of MMR was uneven, with 1.2% among children from the upper-middle class, 4.8% in the village, 6.1% in the urban slum and 10.5% in the poor periurban slum area. Additional impairments were found in 75% of the children with MMR, of which speech impairment was the most common.
Conclusion: The prevalence of MMR was found to be higher in a developing country than in developed countries. It also seemed to be related to poor socioeconomic conditions, as the prevalence in the upper-middle class was comparable to figures from developed countries, while the prevalence in children from poor population groups was much higher.