Abstract
BackgroundTo investigate relationships among neonatal hypothyroidism, family income, and intellectual disability, as well as the combined effects of neonatal hypothyroidism and low family income on intellectual disability.MethodsData were extracted from the National Health Insurance Service-National Sample Cohort from 2002 to 2011. This retrospective study included 91,247 infants. The presence of intellectual disability was based on the disability evaluation system in Korea. Newborn hypothyroidism was identified from diagnosis and prescription codes. Family income was determined from average monthly insurance premiums. Cox proportional hazards models were used to calculate adjusted hazard ratios.ResultsOf the 91,247 infants, 208 were considered to have intellectual disability (29.18 cases per 100,000 person-year). The risk of intellectual disability was higher in infants with hypothyroidism than in those without hypothyroidism (hazard ratio = 5.28, P: < .0001). The risk of intellectual disability was higher in infants with low family income than in those with high family income (hazard ratio = 2.32, P: < .0001). The risk of intellectual disability was higher in infants with hypothyroidism and low family income than in those without hypothyroidism and with high family income (hazard ratio = 36.05, P: < .0001).ConclusionsNeonatal hypothyroidism and low family income were associated with the risk of intellectual disability in Korea. Additionally, neonatal hypothyroidism and low family income significantly increased the risk of intellectual disability. Public health policymakers should consider providing additional resources for alleviating neonatal hypothyroidism among low-income families.
Highlights
Intellectual disability (ID) refers to a significant reduction in the ability to understand, learn, and apply adaptive skills, and appears before 18 years of age [1, 2]
The risk of intellectual disability was higher in infants with hypothyroidism than in those without hypothyroidism
The risk of intellectual disability was higher in infants with hypothyroidism and low family income than in those without hypothyroidism and with high family income
Summary
Intellectual disability (ID) refers to a significant reduction in the ability to understand, learn, and apply adaptive skills, and appears before 18 years of age [1, 2]. Previous studies have reported different causes of ID, such as genetic conditions, problems during pregnancy or birth (congenital hypothyroidism [CHT] and fetal alcohol syndrome), birth defects that affect the brain (asphyxia), problems during infancy and childhood (serious head injury or meningitis) [2,3,4], and socioeconomic status (SES) [5,6,7]. Neonatal hypothyroidism is well known as one of the most common preventable causes of ID, and hypothyroidism can be prevented with early detection and appropriate treatment soon after birth in the first 2–6 postnatal weeks [4, 10]. The clinical signs of NH are not obvious until a later age [13]; early detection through infant screening programs and adequate treatment during early childhood are important to prevent ID. To investigate relationships among neonatal hypothyroidism, family income, and intellectual disability, as well as the combined effects of neonatal hypothyroidism and low family income on intellectual disability
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