Maternal Urinary Fluoride levels during pregnancy and ADHD symptoms during childhood

Abstract

Background and aim. There is little evidence linking fluoride in urinary levels and symptoms or diagnosis of ADHD. In the Basque Country, the fluoridation of drinking water is compulsory for municipalities >30,000 inhabitants. The objective is to analyze the relationships between fluoride levels in urine collected during pregnancy and ADHD symptomatology at 4, 8 and 11 y Methods. Data from 201 to 255 mother-child pairs from the Infancia y Medio Ambiente (INMA) birth cohort with maternal urinary F adjusted for creatinine (MUFcr) during pregnancy and child assessments of ADHD-like behaviors at age of 4, 8 and 11 years was available. ADHD symptoms were reported by ADHD-DSM-IV checklist at age 4, and Conners' Rating Scales-Revised at age 8 and 11. Clinical approach was also carried out using the cut offs of each test. Multiple linear regression and zero inflated binomial regression were used when the outcomes were analyzed as continuous; for a clinical approach, logistic regression was used. Covariates, and biomarkers of neurotoxicants were available. Results: MUFcr levels in pregnancy varied according to the source of drinking water [(mean (95% CI)] being 0.85 (0.77, 0.93) in mothers drinking fluoridated water and 0.45 (0.40, 0.51) in those drinking non-fluoridated water (p<0.01). No association was found between MUFcr levels during pregnancy and inattention, hyperactivity or ADHD score of symptoms at 4, 8 or 11 years. E.g. at the age of 4, for each 1 mg F/g increase across the whole pregnancy, inattention, hyperactivity-impulsivity and ADHD scores did not change significantly: (β =0.16, CI 95%:-1.58, 1.90), (β =0.19, CI 95%: 1.56, 1.95) and (β = 0.35, CI 95%: -2.75, 3.46). Nor was any association observed when a clinical approximation of the problem was used. Conclusions: Higher levels of MUFcr in pregnant women were not associated with global measures of ADHD during childhood