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Abstract
Objectives
Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder showing many neuropsychological deficits. Many environmental risk factors have been thought to increase the risk for the disorder. We examined blood iron levels in children with ADHD and a control group to find an association between iron deficit and diagnosis, neuropsychological characteristics and clinical features.
Methods
An ADHD group (n=50) and control group (n=45) of children 6–12 years of age were recruited. Both groups were diagnosed by semi-structured interview, and they were evaluated using the Korean version of the ADHD Rating Scale (K-ARS), Korean version of IOWA Conner's Rating Scale (K-IOWA), intelligence quotient (IQ), and neurocognitive function tests (continuous performance test, children's color trails test, Stroop color-word test). Iron levels in blood were determined using the inductively coupled plasma mass spectrometry instrument. Independent t-test and correlation were used to determine the relation of blood iron levels with symptom ratings and neurocognitive function. Logistic regression was performed to determine the diagnostic value of blood iron levels.
Results
Blood iron levels were significantly lower in ADHD than in control and showed negative correlation with K-ARS and K-IOWA scores. Blood iron levels showed positive association with IQ and Stroop color-word test results and negative association with results of continuous performance testing. Low blood iron levels predicted the diagnosis of ADHD.
Figures and Tables
Table 3
Correlation between ADHD symptom severity and serum Fe level
*: Correlation is significant at the 0.05 level (2-tailed), †: Correlation is significant at the 0.001 level (2-tailed). K-ARS : Korean ADHD Rating Scale, K-IOWA : Korean version IOWA Connors Rating Scale, T : Total, H : Hyperactivity-impulsivity, I : Inattention, IO : Inattention-overactive, OD : Oppositional-defiant, ADHD : Attention-deficit/hyperactivity disorder
Table 4
Correlation between neuropsychological test results and serum Fe level
*: Correlation is significant at the 0.05 level (2-tailed), †: Correlation is significant at the 0.001 level (2-tailed). ADS : Attention diagnostic system, V : Visual, O : Omission error, A : Auditory, C : Commission error, RT : Response time, SD : Standard deviation, CCTT : Children's color trails test, 1 : 1 total time, 2 : 2 total time, RI : Ratio interference, DI : Difference interference, SCWT : Stroop color-word test, CN : Color naming, WR : Word reading, CW : Color-word, I : Interference
Table 5
Logistic regression results examining the association of serum iron level and ADHD diagnosis
*: Model 1 : including serum Fe, †: Model 2 : including serum Fe, paternal education, ‡: Model 3 : including serum Fe, paternal and maternal education, §: Model 4 : including serum Fe, paternal and maternal education, monthly income, ∥: Model 5 : including serum Fe, paternal and maternal education, monthly income, IQ. SE : Standard error, CI : Confidence interval, IQ : Intelligence quotient, ADHD : Attention-deficit/hyperactivity disorder
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