Research: IQ Reduction
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.
Fluoride exposure and reported learning disability diagnosis among Canadian children: Implications for community water fluoridation
Amanda M. Barberio, Carlos Quiñonez, F. Shaun Hosein, Lindsay McLaren
Canadian Journal of Public Heath
Vol 108, No. 3 (2017)
A certain low dose of fluoride intake may play a potential protective rather than harmful role in cognitive functions; however, high fluoride exposure is a potential risk factor for cognitive impairment.
Mang Li 1 & Yanhui Gao1 & Jing Cui1 & Yuanyuan Li 1 & Bingyun Li 1 & Yang Liu1 &
Jing Sun1 & Xiaona Liu1 & Hongxu Liu1 & Lijun Zhao1 & Dianjun Sun
Biol Trace Elem Res (2016) 172:53–60
Read Full Abstract
Fluoridation of the drinking water is a public policy whose aim is to improve dental health. Although the evidence is clear that fluoride is good for dental health, concerns have been raised regarding potential negative effects on cognitive develop- ment. We study the effects of fluoride exposure through the drinking water in early life on cognitive and non-cognitive ability, education and labor market outcomes in a large-scale setting. We use a rich Swedish register dataset for the cohorts born 1985-1992, together with drinking water fluoride data. To estimate the effect we exploit intra-municipality variation of fluoride, stemming from an exogenous varia- tion in the bedrock. First, we investigate and confirm the long-established positive relationship between fluoride and dental health. Second, we find precisely estimated zero effects on cognitive ability, non-cognitive ability and education. We do not find any evidence that fluoride levels below 1.5 mg/l have negative effects. Third, we find evidence that fluoride improves labor market outcome later in life, which confirms that good dental health is a positive factor on the labor market.
–The Effects of Fluoride In The Drinking Water
Linuz Aggeborn† Mattias O ̈hman
June 27, 2016
Overall, this investigation found no evidence of a detectable adverse outcome on offspring neurobehavioral development associated with maternal fluoride exposure during pregnancy. Fluoride measured in pregnancy urine and plasma was not significantly associated with child’s MDI at any age, and it did not differentially affect MDI at ages 1, 2, and 3. Furthermore, trimester-specific measures of maternal fluoride measures were not significantly associated with offspring MDI.
Fluoride exposure during pregnancy and its effects on childhood neurobehavior: a study among mother-child pairs from Mexico City, Mexico
Deena B. Thomas
A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Environmental Health Sciences) in the University of Michigan 2014
No significant differences in IQ because of fluoride exposure were noted. These findings held after adjusting for potential confounding variables, including sex, socioeconomic status, breastfeeding, and birth weight (as well as educational attainment for adult IQ outcomes).
These findings do not support the assertion that fluoride in the context of CWF programs is neurotoxic. Associations between very high fluoride exposure and low IQ reported in previous studies may have been affected by confounding, particularly by urban or rural status.
Community Water Fluoridation and Intelligence: Prospective Study in New Zealand
Jonathan M. Broadbent, PhD, W. Murray Thomson, BSc, PhD, Sandhya Ramrakha, PhD, Terrie E. Moffitt, PhD, Jiaxu Zeng, PhD, Lyndie A. Foster Page, BSc, PhD, and Richie Poulton, PhD
(Am J Public Health. Published
online ahead of print May 15, 2014: e1–e5. doi:10.2105/AJPH.2013.301857)