Abstract
BackgroundBecause the developing brain of a child is vulnerable to environmental toxins, even very low concentration of neurotoxin can affect children’s neurodevelopment. Lead is a neurotoxic heavy metal which has the harmful effect on the striatal-frontal circuit of brain. This area of the brain is known to be closely related to attention deficit hyperactivity disorder (ADHD) pathophysiology. The primary objective of the present study was to investigate whether elevated blood lead concentration is a risk factor for ADHD. The secondary objective was to examine the association between blood lead concentration and symptom severity.MethodsWe conducted a frequency-matched, hospital-based case-control study with 114 medically diagnosed ADHD cases and 114 controls. The participants were matched for age and sex. The diagnoses of ADHD were assessed with semi-structured diagnostic interviews. The participants completed the continuous performance test (CPT), and their parents completed the ADHD-rating scale (ADHD-RS). Blood lead concentrations were measured by using graphite furnace atomic absorption spectrometry featuring Zeeman background correction.ResultsChildren with ADHD exhibited blood lead concentrations that were significantly higher than those of the controls ( 1.90 ± 086 μg/dℓ vs. 1.59 ± 0.68 μg/dℓ, p = 0.003). The log transformed total blood lead concentration was associated with a higher risk of ADHD (OR: 1.60, 95 % CI: 1.04–2.45, p < 0.05). The analysis also revealed that the children with blood lead concentrations above 2.30 μg/dℓ were at a 2.5–fold (95 % CI: 1.09–5.87, p < 0.05) greater risk of having ADHD. After adjusting for covariates, our multivariate regression models indicated that blood lead concentrations were not significantly associated with ADHD-RS or CPT profiles among the ADHD cases.ConclusionEven low blood lead concentrations are a risk factor for ADHD in children. This study warrants primary prevention policies to reduce the environmental lead burden. Future studies may be required to ascertain the effects of lead on symptom severity in ADHD.
Highlights
Because the developing brain of a child is vulnerable to environmental toxins, even very low concentration of neurotoxin can affect children’s neurodevelopment
Among the environmental factors that are suspected to be associated with attention deficit hyperactivity disorder (ADHD), lead exposure has been implicated in the etiology of ADHD [4]
Association between blood lead concentration and ADHD symptom severity After adjusting for the covariates, our multivariate regression models indicated that blood lead concentrations were not significantly associated with ADHD-rating scale (ADHD-RS) or continuous performance test (CPT) profiles the ADHD cases (Table 4)
Summary
Because the developing brain of a child is vulnerable to environmental toxins, even very low concentration of neurotoxin can affect children’s neurodevelopment. ADHD is the most common neurodevelopmental disorder in childhood, with a worldwide prevalence of approximately 5 % [1, 2] Both genetic and environmental factors are involved in the etiology of ADHD. The brain regions that are most vulnerable to lead exposure are the prefrontal cortex, basal ganglia, hippocampus, and cerebellum [6] Dysfunctions of these regions have been postulated to be involved in ADHD pathophysiology [7]. Reduced dopamine activity in striatum has been implicated in the core symptoms of ADHD [10, 11] Overall, these studies revealed that lead adversely affects the dopamine system in the prefrontal-striatal network, which is linked to the core pathophysiology of ADHD
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