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Fluoride exposure and reported learning disability diagnosis among Canadian children: Implications for community water fluoridation

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Abstract

OBJECTIVES: Recent studies have connected increased fluoride exposure with increased risk of neurodevelopmental-related outcomes, such as ADHD (attention deficit hyperactivity disorder) and lower IQ in children. Our primary objective was to examine the association between fluoride exposure and reported diagnosis of a learning disability among a population-based sample of Canadian children aged 3–12 years.

METHODS: We analyzed data from Cycles 2 and 3 of the Canadian Health Measures Survey. Four measures of fluoride exposure were available: 1) urinary fluoride (μmol/L), 2) creatinine-adjusted urinary fluoride (μmol/mmol), 3) specific gravity-adjusted urinary fluoride (μmol/L), and 4) fluoride concentration of tap water (mg/L) (Cycle 3 only). Diagnosis of a learning disability (yes/no) was based on parental- or self-report. Associations were examined using logistic regression (where possible), unadjusted and adjusted for covariates.

RESULTS: When Cycles 2 and 3 were examined separately, reported learning disability diagnosis was not significantly associated with any measure of fluoride exposure in unadjusted or adjusted models. When Cycles 2 and 3 were combined, a small but statistically significant effect was observed such that children with higher urinary fluoride had higher odds of having a reported learning disability in the adjusted model (p = 0.03). However, the association was not observed in models that used creatinine-adjusted urinary fluoride and specific gravity-adjusted urinary fluoride, which are believed to be more accurate measures due to their correction for urinary dilution.

CONCLUSION: Overall, there did not appear to be a robust association between fluoride exposure and parental- or self-reported diagnosis of a learning disability among Canadian children.

Résumé

OBJECTIFS: Des études récentes ont révélé que la croissance de l’exposition au fluorure augmente le risque de maladies reliées au développement des neurones telles que, TDAH (trouble déficitaire de l’attention, avec ou sans hyperactivité) et de QI moins élevés chez les enfants. Notre objectif principal est d’examiner le lien entre l’exposition au fluorure et les diagnostics publiés sur les troubles d’apprentissage selon un échantillon de la population d’enfants âgés de 3 à 12 ans.

MÉTHODES: Nous avons analysé les données des cycles 2 et 3 de l’Enquête canadienne sur les mesures de la santé. Quatre mesures de fluorure étaient disponibles: 1) fluorure urinaire (μmol/L), 2) fluorure urinaire normalisée par la créatinine (μmol/mmol), 3) fluorure urinaire spécifique normalisée pour la gravité (μmol/L), et 4) concentration de fluorure de l’eau du robinet (mg/L) (Cycle 3 seulement). Le diagnostic des troubles d’apprentissage (oui ou non) était fondé sur les rapports parentaux ou sur l’auto-évaluation. Les liens ont été examinés en utilisant la régression logistique (là où c’était possible), données non corrigées et corrigées pour les covariables.

RÉSULTATS: Lorsque les cycles 2 et 3 ont été examinés séparément, le diagnostic sur les troubles d’apprentissage ne présentait aucun lien significatif avec les mesures d’exposition au fluorure, dans les modèles corrigés ou non corrigés. Lorsque les cycles 2 et 3 ont été regroupés, un léger effet, mais dont la signification statistique a été observée comme quoi les enfants ayant démontré un taux de fluorure urinaire plus élevé avaient plus de chances d’avoir des troubles d’apprentissage selon le modèle corrigé (p = 0.03). Cependant, ce lien n’a pas été observé dans les modèles qui utilisaient des taux de fluorure urinaire corrigés pour la créatinine et corrigés pour la gravité spécifique, lesquels sont censés être plus précis en raison de la correction pour la dilution urinaire.

CONCLUSION: En général, nous n’avons trouvé aucun lien solide entre l’exposition au fluorure et les diagnostics des parents ou des auto¬évaluations parmi les enfants canadiens quant aux troubles d’apprentissages.

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Authors and Affiliations

  1. Department of Cancer Epidemiology and Prevention Research, Alberta Health Services, Edmonton, AB, Canada

    Amanda M. Barberio BHSc (hons), MSc

  2. Department of Community Health Sciences and O’Brien Institute for Public Health, University of Calgary, TRW3, 3280 Hospital Dr. NW, Calgary, AB, T2N 4Z6, Canada

    Amanda M. Barberio BHSc (hons), MSc & Lindsay McLaren PhD

  3. Dental Public Health, Faculty of Dentistry, University of Toronto, Toronto, ON, Canada

    Carlos Quiñonez DMD, MSc, PhD, FRCD(C)

  4. Faculty of Medicine, University of Queensland, St Lucia, QLD, Australia

    F. Shaun Hosein MD, MSc

Authors
  1. Amanda M. Barberio BHSc (hons), MSc
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  2. Carlos Quiñonez DMD, MSc, PhD, FRCD(C)
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  3. F. Shaun Hosein MD, MSc
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  4. Lindsay McLaren PhD
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Corresponding author

Correspondence to Lindsay McLaren PhD.

Additional information

Funding: Lindsay McLaren holds an Applied Public Health Chair from CIHR (Institute of Population & Public Health and Institute of Musculoskeletal Health & Arthritis), the Public Health Agency of Canada, and Alberta Innovates - Health Solutions.

Conflict of Interest: None to declare.

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Barberio, A.M., Quiñonez, C., Hosein, F.S. et al. Fluoride exposure and reported learning disability diagnosis among Canadian children: Implications for community water fluoridation. Can J Public Health 108, e229–e239 (2017). https://doi.org/10.17269/CJPH.108.5951

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  • DOI: https://doi.org/10.17269/CJPH.108.5951

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