Intellectual Disability in a Birth Cohort: Prevalence, Etiology, and Determinants at the Age of 4 Years

Abstract

Background: Intellectual disability (ID), characterized by impairments in intellectual function and adaptive behavior, affects 1-3% of the population. Many studies investigated its etiology, but few are cohort studies in middle-income countries. Aims: To estimate prevalence, etiology, and factors related to ID among children prospectively followed since birth in a Southern Brazilian city (Pelotas). Methods: In 2004, maternity hospitals were visited daily and births were identified. Live-born infants (n = 4,231) whose family lived in the urban area have been followed for several years. At the age of 2 and 4 years, performances in development and intelligence tests were evaluated using the Battelle Developmental Inventory and Wechsler Intelligence Scale, respectively. Children considered as having developmental delay were invited to attend a genetic evaluation. Results: At 4 years of age, the prevalence of ID was 4.5%, and the etiology was classified into 5 groups: environmental (44.4%), genetic (20.5%), idiopathic (12.6%), neonatal sequelae (13.2%), other diseases (9.3%). Most children presented impairment in two or more areas of adaptive behavior. There was no difference in prenatal care attendance or maternal schooling among the groups. Conclusion: For about 40% of children, ID was attributed to nonbiological factors, suggesting that the rate may be reduced with appropriate interventions early in life.

Pre and postnatal characteristics of children and adolescents with intellectual disability

“…The analysis of the sociodemographic variables showed that few mothers of children and adolescents with ID had completed secondary education. In agreement with previous studies, low maternal education is pointed out as a factor associated with ID 5,6,15 . A recent systematic review and meta-analysis found 100% higher risk of ID among children and adolescents whose mothers had low education levels 5 .…”

“…However, there are some known factors that may occur in prenatal and neonatal periods. Factors may be biomedical, e.g., chromosome disorders; behavioral, such as drug and alcohol abuse by mothers during pregnancy; social, such as lack of access to prenatal care and health care during and after birth, and also educational, for example, educational disadvantageand lack of family support [5][6][7] .…”

“…In a recent systematic review and meta-analysis which examined the influence of these variables on development of ID, it was found that maternal characteristics, such as low education, alcohol abuse and smoking during pregnancy, diabetes and hypertension, were associated with this disorder, because they affect children's cognitive and behavioral development 6 . In addition, advanced maternal age, premature birth, prelabor rupture of membranes, cesarean delivery and low birth weight are also factors that influence the development of ID 5,[8][9][10] .…”

The diagnostic yield of intellectual disability: Combined whole genome low-coverage sequencing and medical exome sequencing

“…Intellectual disability (ID) is characterized by impairment of cognitive and social adjustment due to brain damage or incomplete development, which accounted for a prevalence of about 1-3% in worldwide [1][2][3][4] . ID is a complicated neurodevelopmental disorder that might be affected by a series of heterogeneous factors such as environmental, genetic, idiopathic, neonatal sequelae and other diseases 2 . Many studies have been conducted to reveal the genetic etiology of ID and there are more than 600 genes and 130 rare copy number variations (CNVs) involved in cause of ID [5][6][7][8][9] .…”

The diagnostic yield of intellectual disability: Combined whole genome low-coverage sequencing and medical exome sequencing

“…Intellectual disability (ID) is characterized by impairment of cognitive and social adjustment due to brain damage or incomplete development, which accounted for a prevalence of about 1-3% in worldwide 1 − 4 . ID is a complicated neurodevelopmental disorder that might be affected by a series of heterogeneous factors such as environmental, genetic, idiopathic, neonatal sequelae and other diseases 2 . Many studies have been conducted to reveal the genetic etiology of ID and there are more than 600 genes and 130 rare copy number variations (CNVs) involved in cause of ID 5 − 9 .…”