Summary: A pilot study found a possible link between the long-term consumption of water with elevated fluoride levels and cognitive impairments in children.
Conducted in rural Ethiopia, where wells exhibit varied natural fluoride levels, researchers assessed the cognitive abilities of 74 children through drawing and memory tests. Findings suggest a correlation between high fluoride exposure and increased errors on these tests.
While the exact causal relationship remains uncertain, the study emphasizes the need for further research on fluoride’s potential neurotoxic effects, especially during early brain development.
The study was conducted in regions of Ethiopia with fluoride levels ranging from 0.4 to 15.5 mg/L, far exceeding the WHO’s recommendation of below 1.5 mg/L.
Children exposed to higher fluoride levels in drinking water made more errors in standard cognitive tests.
Over 200 million people globally are believed to be exposed to high fluoride levels in their drinking water.
Source: Tulane University
Long-term consumption of water with fluoride levels far above established drinking water standards may be linked to cognitive impairments in children, according to a new pilot study from Tulane University.
The study, published in the journal Neurotoxicology and Teratology, was conducted in rural Ethiopia where farming communities use wells with varying levels of naturally occurring fluoride ranging from 0.4 to 15.5 mg/L. The World Health Organization recommends fluoride levels below 1.5 mg/L.
Researchers recruited 74 school-aged children and rated their ability to draw familiar objects such as a donkey or a house, with scores reflecting any missing details. They used a standard computerized memory test which is language and culture neutral as another tool to measure cognitive ability.
The study found that higher exposure to fluoride in drinking water was linked to more errors on the drawing and memory tests. Lead author Tewodros Godebo, assistant professor of environmental health sciences at Tulane University School of Public Health and Tropical Medicine, said the “causal relationship between fluoride exposure and neurotoxicity remains unclear” but he hopes these preliminary findings will spur more research into the potential cognitive impacts of fluoride exposure.
“Though further epidemiological studies are needed to validate the findings, these results add to the growing concern about the potential neurotoxic effects of fluoride, especially during early brain development and childhood,” Godebo said. “These tests affirmed a clear association between high fluoride and cognitive impairment.”
Fluoride is essential for preventing tooth decay. However, excess intake of fluoride has been linked to lower IQs in past epidemiological studies in rural communities in China and India.
Additionally, past animal research has shown that fluoride can cross the placenta and blood-brain barriers. In regions with no alternative water sources, this means excess fluoride exposure could be a chronic issue that begins at conception.
Over 200 million people worldwide are estimated to be exposed to high fluoride levels in their drinking water. The Ethiopian Rift Valley, where this study was conducted, is an ideal research area for investigations of potential impacts because those raised in the area have consistent exposure to stable, naturally occurring fluoride levels and share similar lifestyles with surrounding villages, limiting the risk of confounding factors.
Godebo hopes to replicate the results in Ethiopia with a larger cohort of children and study the cognition of children in low-fluoride Ethiopian communities for potential signs of cognitive impact.
“We have a unique opportunity to study low fluoride communities in the same setting as high fluoride communities, so we can determine if fluoride is a neurotoxicant at low levels,” Godebo said.
“Such studies are important to the public and government agencies to determine the safety and risk of water fluoridation in drinking water supply systems.”
Co-authors for the study included Nati Pham and Arti Shankar of Tulane University, Marc Jeuland of Duke University, Amy Wolfe of University of Kentucky, and Redda Tekle-Haimanot and Biniyam Alemayehu of Addis Ababa University.
About this neurodevelopment and cognition research news
Association between fluoride exposure in drinking water and cognitive deficits in children: A pilot study
Fluoride (F) exposure in drinking water may lead to reduced cognitive function among children; however, findings largely remain inconclusive.
In this pilot study, we examined associations between a range of chronic F exposures (low to high: 0.4 to 15.5 mg/L) in drinking water and cognition in school-aged children (5–14 years, n = 74) in rural Ethiopia. Fluoride exposure was determined from samples of community-based drinking water wells and urine.
Cognitive performance was measured using: 1) assessments of ability to draw familiar objects (donkey, house, and person), and 2) a validated Cambridge Neuropsychological Test Automated Battery’s (CANTAB) Paired Associate Learning (PAL), which examines memory and new learning and is closely associated with hippocampus function of the brain.
Associations between F and cognitive outcomes were evaluated using regression analysis, adjusting for demographic, health status, and other covariates.
The median (range) of water and urine F levels was 7.6 (0.4–15.5 mg/L) and 6.3 (0.5–15.7 mg/L), respectively; these measures were strongly correlated (r = 0.74), indicating that water is the primary source of F exposure.
Fluoride in drinking water was negatively associated with cognitive function, measured by both drawing and CANTAB test performance. Inverse relationships were also found between F and drawing objects task scores, after adjusting for covariates (p < 0.05).
Further analysis using CANTAB PAL tasks in the children confirmed that F level in drinking water was positively associated with the number of errors made by children (p < 0.01), also after adjusting for covariates (p < 0.05).
This association between water F and total errors made became markedly stronger as PAL task difficulty increased. Fluoride exposure was also inversely associated with other PAL tasks the number of patterns reached, first attempt memory score and mean errors to success.
These findings provide supportive evidence that high F exposures may be associated with cognitive deficits in children. Additional well-designed studies are critically needed to establish the neurotoxicity of F in children and adults exposed to both low levels known to protect dental caries, as well as excess F levels in drinking water.