A Case Control Study on Blood Lead, Urinary Cotinine and Attention Deficit Hyperactivity Disorder in Children

Abstract

<Background>As risk factors for attention deficit hyperactivity disorder (ADHD), prenatal smoking and lead exposure and their synergistic effect of simultaneous exposure have been reported. < Aims>The purpose of this study is to investigate associations between blood lead, urinary cotinine levels and ADHD including a possible synergistic effect of the lead and cotinine on ADHD in children. <Method> Based on a community survey for ADHD screening using the Korean version of ADHD rating scale in elementary schools of Cheonan city, a case control study was designed to examine environmental risk factors for ADHD. Cases and controls were confirmed by a pediatric psychiatrist through a thorough clinical work-up. Controls were selected by individual age and gender matching with the cases. A total of 214 cases and 237 controls aged 6-10 were included in the present study. Measurements of blood lead concentration and urinary cotinine level and questionnaire administration to obtain information on general characteristics, socio-demographic and various confounders were done at the time of participants’ hospital visits. Analysis was performed using multiple logistic regression model adjusted for confounders and covariates. <Results>Geometric means (geometric standard deviation) of blood lead and urinary cotinine levels were 1.64 (1.46) ug/dL and 1.78 (3.81) ng/mL in ADHD cases and 1.47 (1.47) ug/dL and 1.15 (2.73) ng/mL in controls, respectively. Risk of ADHD associated with blood lead level: odds ratios of 1.90 (95% confidence intervals =1.06-3.38) for the highest quartile compared to the lowest of lead level. ADHD risk showed a significant increase according to increasing urinary cotinine level (p-trend=0.004). However, the synergistic effect of blood lead and urinary cotinine on the risk of ADHD was not significant. <Conclusion>Exposure to lead and tobacco smoke associated with risk of ADHD and a non-significant synergistic effect was found in children.