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



To estimate prevalence, etiology, and factors related to ID among children prospectively followed since birth in a Southern Brazilian city (Pelotas).



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.



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.



For about 40% of children, ID was attributed to nonbiological factors, suggesting that the rate may be reduced with appropriate interventions early in life.
Programa de Pós-Graduação em Saúde da Criança e do Adolescente, UFRGS, Porto Alegre, Brazil.
Simone M
SM
Karam
Aluísio J D
AJ
Barros
Alícia
A
Matijasevich
Iná S
IS
Dos Santos
Luciana
L
Anselmi
Fernando
F
Barros
Sandra
S
Leistner-Segal
Têmis M
TM
Félix
Mariluce
M
Riegel
Sharbel W
SW
Maluf
Roberto
R
Giugliani
Maureen M
MM
Black
D001938:Brazil / Q000453:epidemiology; D002675:Child, Preschool; D015331:Cohort Studies; D004185:Disability Evaluation; D019988:Children with Disabilities / Q000706:statistics & numerical data*; D004777:Environment; D005260:Female; D005820:Genetic Testing / Q000379:methods / Q000706:statistics & numerical data; D006801:Humans; D008607:Intellectual Disability / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology; D007361:Intelligence Tests; D008297:Male; D020380:Needs Assessment; D015995:Prevalence