Fluoride Exposure and Children’s IQ Scores – A Systematic Review and Meta-Analysis

Published In:

JAMA Pediatrics

Publication Year:

2025

Study Design

This research is a systematic review and meta-analysis of epidemiological studies investigating the association between fluoride exposure and children's IQ scores.

Funding Sources

The study was supported by the National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health. No conflicts of interest were reported.

PICO Framework – what was studied and how?

Population:

Children with prenatal or postnatal fluoride exposure.

Intervention:

Exposure to fluoride through drinking water, food, and other sources.

Comparison:

Children with lower fluoride exposure or no fluoride exposure.

Outcomes:

Cognitive performance and IQ scores, measured through standardized tests.

In Paragraph Form:

This meta-analysis reviewed 74 epidemiological studies to assess the impact of fluoride exposure on children's IQ scores. The researchers compared cognitive outcomes between children with different levels of fluoride exposure, using both group-level and individual-level exposure data. The primary focus was on whether fluoride in drinking water and urine correlated with lower IQ scores.

Inclusion and Exclusion Criteria

Inclusion Criteria:

• Studies that reported children's IQ scores, fluoride exposure levels, and effect sizes.
• Studies with group-level or individual-level fluoride exposure assessments.
• Both cross-sectional and cohort studies were included.

Exclusion Criteria:

• Studies that did not measure fluoride exposure levels.
• Studies without IQ measurements.
• Studies with confounding factors like arsenic or iodine co-exposure that could influence results.

Demographics and Study Design

• 74 studies included:
  • 64 cross-sectional studies
  • 10 cohort studies
• Geographic distribution:
  • China (45 studies)
  • India (12 studies)
  • Iran (4 studies)
  • Mexico (4 studies)
  • Canada (3 studies)
  • Other countries (Denmark, New Zealand, Pakistan, Spain, Taiwan)
• Risk of bias assessment:
  • 52 studies rated high risk of bias
  • 22 studies rated low risk of bias

Primary Outcome Variables and Results

Key Findings:

• Overall association: Children with higher fluoride exposure had lower IQ scores.
• Group-level fluoride exposure (59 studies, 20,932 children):
  • Pooled Standardized Mean Difference (SMD): -0.45 (95% CI, -0.57 to -0.33, p < 0.001)
• Fluoride in drinking water (31 studies):
  • Dose-response relationship found.
  • IQ score decrease significant at >1.5 mg/L fluoride levels.
• Urinary fluoride exposure (20 studies):
  • Dose-response association remained significant even at lower fluoride levels (<1.5 mg/L).
• Individual-level fluoride exposure (13 studies):
  • 1-mg/L increase in urinary fluoride = IQ decrease of 1.63 points (95% CI, -2.33 to -0.93, p < 0.001)
  • Among low risk-of-bias studies: IQ decrease was 1.14 points per 1-mg/L fluoride.

Conclusions

This systematic review and meta-analysis found an inverse association between fluoride exposure and children's IQ scores. The results suggest that fluoride exposure, even at levels below 1.5 mg/L, may impact cognitive development. The study calls for further research, particularly prospective cohort studies, to better assess risks at lower fluoride levels.

Discussion: Strengths and Limitations

Strengths:

• Large dataset: 74 studies covering over 20,000 children.
• Multiple exposure sources: Evaluated fluoride in water, urine, and food.
• Dose-response analysis: Showed a clear relationship between fluoride levels and IQ.

Limitations:

• High heterogeneity: Variability in study designs and methodologies.
• Potential confounders: Some studies did not fully account for other environmental toxins.
• No U.S.-based studies: Findings are based on populations in China, India, and other countries.

Citation

Taylor KW, Eftim SE, Sibrizzi CA, et al. Fluoride Exposure and Children’s IQ Scores: A Systematic Review and Meta-Analysis. JAMA Pediatrics. 2025;179(3):282-292.
https://pubmed.ncbi.nlm.nih.gov/

Visual Aids

Simple Chart: Fluoride Exposure and IQ Reduction