Prenatal Fluoride Exposure and Symptoms of Attention Deficit Hyperactivity Disorder (ADHD)

INTRODUCTION: Epidemiologic and animal-based studies have raised concerns about the potential neurotoxicity of fluoride exposure as manifested by deficits in IQ and problems with attention. To date, no prospective epidemiologic studies have examined the effects of prenatal fluoride exposure using fluoride biomarkers and sensitive measures of attention.OBJECTIVE: To test the association between prenatal fluoride exposure and symptoms associated with attention-deficit and hyperactivity disorder (ADHD) in 213 Mexican children aged 6-12 years old enrolled in the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) birth cohorts between1997 to 2006.METHOD: We measured urinary fluoride levels during pregnancy and adjusted them for urinary creatinine (MUF_cr). The Conners’ Rating Scales-Revised (CPRS-R) was completed by mothers as a behavioural measure of attention problems, and the Conners’ Continuous Performance Test (CPT-II) was administered to each child to assess sustained attention and inhibitory control. We used gamma regression analyses to examine associations between MUFcr and measures of attention, adjusting for covariates.RESULTS: The mean MUF_cr level for all women was 0.85 mg/L (95% CI; 0.81, 0.90) and the Interquartile Range (IQR) was 0.46. In multivariate-adjusted models, a 0.5 mg/L increase in MUF_cr (approximately IQR) corresponded to significantly higher CPRS-R scores for DSM-IV Inattention (2.84 points, 95% CI: 0.84, 4.84); Cognitive Problems and Inattention, (2.54 points, 95% CI: 0.44, 4.63), DSM-IV Total ADHD Index (2.38 points, 95% CI: 0.42, 4.34) and ADHD Index (2.47 points; 95% CI: 0.43, 4.50). The shape of the associations suggested a possible celling effect. No significant associations were found with outcomes on the CPT-II. Sensitivity analyses did not appreciably alter the results.CONCLUSION: Higher levels of prenatal fluoride exposure were associated with higher symptoms of ADHD measured by CPRS-R in the offspring at age 6–12 years.