Fluoride exposure and cognitive neurodevelopment: Systematic review and dose-response meta-analysis

Area of Science:

• Environmental Health
• Neuroscience
• Pediatrics

Background:

• Uncertainties persist regarding fluoride exposure's impact on children's cognitive neurodevelopment.
• Assessing the dose-response relationship between fluoride exposure and intelligence quotient (IQ) is crucial.

Approach:

• A systematic review and meta-analysis synthesized data from 33 eligible studies.
• A one-stage dose-response meta-analysis using a cubic spline random-effects model was employed.
• Compared IQ scores between highest and lowest fluoride exposure categories.

Key Points:

• A summary mean difference of -4.68 IQ points was observed comparing highest to lowest fluoride exposure categories.
• Drinking water fluoride showed a significant association ( -5.60 IQ points), while urinary fluoride showed a weaker trend (-3.84 IQ points).
• IQ decrease was substantially linear with increasing water fluoride above 1 mg/L, becoming steeper above 2 mg/L.

Conclusions:

• Most studies indicate an adverse effect of fluoride on children's IQ, even at low exposure levels.
• The association was stronger in studies with a high risk of bias; no adverse effect was found in the single low-risk study.
• Residual confounding cannot be ruled out, necessitating further prospective, low-risk bias studies.