Impact of specific medical interventions on reducing the prevalence of mental retardation

Objective: To explore the impact of medical interventions on reducing the prevalence of mental retardation (MR) in the United States over the last 50 years. Design: We reviewed the medical literature and other data from 1950 to 2000 to construct estimates of the general and condition-specific prevalence of MR in the United States over time. We further explored the existing literature to document historically important influences on condition-specific prevalence, including the year that an effective intervention was introduced, the likelihood of success of the intervention, and the availability of such interventions nationwide. Specific conditions included congenital syphilis, Rh hemolytic disease of the newborn, measles, Haemophilus influenzae type B meningitis, congenital hypothyroidism, phenylketonuria, and congenital rubella syndrome. Setting: Twentieth-century North America. Participants: Children with MR or 1 of the 7 specific conditions listed earlier. Main Outcome Measures: Case-specific and general prevalence of MR from 1950 to 2000. Results: The prevalence of MR caused by a number of specific medical conditions has decreased sharply over the last 50 years. However, the incidence of each of these conditions is relatively low, and cases of MR due to these conditions represent, at most, 16.5% of the total number of cases of MR in 1950. Conclusion: Although specific medical interventions have prevented thousands of cases of MR, their contribution to the overall prevalence of MR is relatively small.