Epidemiology of prenatal genetic and environmental factors of mental retardation in cuba.

INTRODUCTION

One of the most sensitive disabilities in human beings is intellectual disability. In April, 2003, a 10-month study was completed of all persons in Cuba with mental retardation (MR), producing results that included epidemiological variables on a national scale.

OBJECTIVE

Through follow-up research, this paper describes and analyzes 4 prenatal factors associated with MR: Down syndrome (DS), fragile X syndrome (FXS), consanguinity, and maternal alcohol use during pregnancy, in order to provide recommendations for health system decision-makers on consolidating prevention strategies at the community level and improving individual attention to persons with MR. Materials &

METHODS

All studies were carried out on the basis of strict ethical principles. Data for the 4 prenatal factors was gleaned from the national study's database. Additional data on affected individuals was obtained through home visits. A previously developed screening instrument was used for clinical genetic analysis to classify possible MR causal factors as prenatal, perinatal, postnatal, psychosis, and unclassifiable. Prenatal included causal factors such as: genetic (by clinical genetic examination, metabolic screening in urine, and routine karyotypes); nonspecific (evidence of prenatal causal factor without diagnosis of genetic or environmental etiology); and environmental (prenatal medical history of biological, physical, or chemical teratogens, endocrine-metabolic diseases, or other maternal diseases known to affect fetal neurodevelopment). Frequency, prevalence, and percentages were reported using a descriptive statistical method. Impact of interventions and actions over time were also compared.

RESULTS

MR prevalence in Cuba is 1.25%, lower than the value of 2%-3% reported in developed countries. National prevalence of DS was found to be 4.3 per 10,000 population, representing 22.1% of persons with MR attributed to an ascertained genetic cause. FXS prevalence in a population of individuals of both sexes with MR, initially classified as nonspecific prenatal, psychosis, and unclassifiable, was 2.5 per 1,000 of that population; however, in males of the same population, prevalence was 3.7 per 1,000. At this first stage, such results indicate that this syndrome contributes biologically to the 1.46:1 male/female ratio among the 140,489 individuals with MR. Maternal alcohol use during pregnancy was found in 4.22% of persons with MR and consanguinity was present in 6.89% of the population with MR (10.9% of persons with mild prenatal MR and 14.2% with severe MR). This national data is subdivided by regions and provinces in this paper.

CONCLUSIONS

Prevalence of MR in Cuba is lower than reference values for developed countries. Knowledge generated by this study about 4 specific causes of MR constitutes pioneering research in the Cuban context, contributing to the field of medical genetics. The results offer the basis for formulation of new scientific contributions related to MR genetics as well as preventive approaches to such genetic factors as consanguinity and to environmental factors such as maternal alcohol use during pregnancy, which affect or target embryo-fetal development of the nervous system.