Chronic Exposure to Fluoride Affects Cognitive Function in Children

by | Dec 13, 2023 | 2023, Brain Health, Cognitive Health, Fluoride, Infant and Children's Health

Written by Chrystal Moulton, Staff Writer. Overall, drawing scores were significantly inversely associated with fluoride concentration in the drinking water (R2= 0.027, P= 0.019).

young boyFluoride is essential for preventing cavities when consumed at an optimal level (0.71 mg/L)1. However, when excessive amounts of fluoride are consumed, it can lead to dental and skeletal fluorosis2. Excessive exposure to fluoride has also been linked to cognitive affects in children. However, research in this area is not consistent3. Research has shown fluoride exposure can damage the developing brain in utero4. It has also been shown to impair the myelin sheath, neurotransmitters, inhibit several neuronal enzymes, and increase lipid peroxidation5,6. Some geographic regions are particularly susceptible to increased exposure to fluoride. The main Ethiopian Rift Valley is one region where individuals are chronically exposed to fluoride through groundwater. In a prior trial, researchers conducted a study to map fluoride concentration in groundwater sources within the valley and the corresponding concentration of fluoride in each water source. In the current trial, researchers investigated the relationship between exposure to fluoride from drinking water and cognitive performance in children3.

Seventy-four children in the main Ethiopian Rift Valley between the ages of 5-14 years old were enrolled in this cross-sectional study. Eight communities with fluoride concentration between 0.41 to 15.5 mg/L in the drinking water were selected. Each community is a homogeneous rural population primarily dependent on farming. All eight communities share common living conditions, livelihood, culture, and diet. All children enrolled for this study were born and raised in the selected communities. Inclusion criteria were: permanent residency in the community, age 5-14 years old, consent to participate obtained from both parents and children, and duration of residency equal to the age of the well sampled for the trial (their main water source). Demographic data, anthropometric data, daily water intake, urine sample, and spot your samples were collected from the children. Researchers tested fluoride content in both urine and drinking water. Arsenic and lead content was also tested in both urine and water samples. Cognitive function was assessed with two tests. The first test was a drawing task. The children were asked to draw a donkey, a house, and a person. Each drawing was then scored based on completeness and complexity. The second test was the Cambridge neural psychological test automated battery (CANTAB®) of which researchers selected the paired association learning test (PAL). The CANTAB® PAL, which tests spatial memory, is administered by a touch screen interface and is culturally and linguistically neutral. Children were given 2 practice tests to familiarize themselves with the software. Primary outcomes were the number of patterns reached (higher score is better) and total errors adjusted (lower score is better). Researchers evaluated the effect fluoride exposure from drinking water to the CANTAB® PAL test and drawing scores.

Of 74 children enrolled in this trial, urine samples were collected from 68 children. The average age was 10 years old with 54.4% the children being male. Majority of the children were underweight (wt= 16.2 kg/m2, BMI= 15.4 ±1.57 kg/m2). Also, 88.2% of the children ingested concentrations of fluoride that exceeded The US EPA No-Observed-Adverse-Effects level [NOAEL= 0.06 mg/kg/d]. Researchers observed a strong correlation between fluoride concentration in drinking water and the fluoride in the children’s urine (R2= 0.74, P< 0.001) suggesting their drinking water as the main source of fluoride exposure. A negative association was also observed between fluoride and lead levels in the drinking water (R2= -0.61, P< 0.001). Researchers assessed the association between fluoride in drinking water and drawing scores by distributing the communities into three groups based on fluoride concentration in groundwater. Group 1 were communities with < 3mg/L fluoride in the drinking water. Group 2 and group 3 communities had concentrations of >3-8 mg/L fluoride and >8-15.5 mg/L fluoride in the drinking water, respectively. Group 1 communities were used as a reference point. Linear regression analysis confirmed an inverse association between fluoride concentration in drinking water and drawing scores of a donkey even after adjusting for other factors (R2= 0.075, P= 0.024). No significant association was observed with a drawing of a person (R2= 0.015, P= 0.32) and of the house (R2= 0.023, P= 0.21). Overall, drawing scores were significantly inversely associated with fluoride concentration in the drinking water (R2= 0.027, P= 0.019).  After adjusting for confounders, children from Group 3 communities had significantly lower scores for the donkey drawing (R2 = – 3.56, P = 0.024) compared to Group 1 and 2 communities. No statistically significant data was observed with the drawing of a person and of a house. In the CANTAB® PAL test, after adjusted for other factors, PAL total errors adjusted score was significantly associated with fluoride concentration in the drinking water (P= 0.05). No significant interaction was observed between difficulty of the task and concentration of fluoride in the drinking water.

Overall, this study showed that children exposed to high concentrations of fluoride in drinking water had significant cognitive deficit. Additional studies will be needed to establish the neurotoxic level of fluoride which effects cognitive performance.

Source: Godebo, Tewodros Rango, Marc Jeuland, Redda Tekle-Haimanot, Biniyam Alemayehu, Arti Shankar, Amy Wolfe, and Nati Phan. “Association between fluoride exposure in drinking water and cognitive deficits in children: A pilot study.” Neurotoxicology and Teratology 100 (2023): 107293.

© 2023 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/bync-nd/4.0/).

Click here to read the full text study.

Posted December 13, 2023.

Chrystal Moulton BA, PMP, is a 2008 graduate of the University of Illinois at Chicago. She graduated with a bachelor’s in psychology with a focus on premedical studies and is a licensed project manager. She currently resides in Indianapolis, IN.

References:

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