SEVERE MENTAL-RETARDATION IN 2-MONTH-OLD TO 24-MONTH-OLD CHILDREN IN LAHORE, PAKISTAN - A PROSPECTIVE COHORT STUDY

Severe mental retardation (developmental quotient (DQ) < 50) was inves tigated in 1303 children from 2 to 24 months of age, born during 1984- 87 in four population groups representing different socioeconomic leve ls in and around Lahore, Pakistan. The incidence per 1000 live births was 22 in the periurban slum, 9 in the urban slum, 7 in the village an d 4 in the upper middle class group. The aetiology was prenatal in 79% , perinatal in 14% and untraceable in 7% of cases. Down's syndrome was the most common cause of severe;mental retardation (36%). Impairments were studied at 2 years of age. Impairment of language was present in all, while locomotor dysfunction was seen in 89% of cases. Epilepsy a nd cerebral palsy were each present in 22% of cases. Mortality among t hese severely mentally retarded children was 36%.