Fluoride Action Network

Abstract

Highlights

  • Maternal fluoride levels were associated with better cognitive scores in childhood.
  • The neuropsychological association is gender dependent; only seen in boys.
  • Positive associations do not disappear after adjustment by different covariates.
  • A potential positive neuropsychological association at low fluoride levels cannot be excluded.

Background

Cross-sectional and prospective studies have provided evidence of the neurotoxic effect of early exposure to fluoride (F) in pregnancy. It has been negatively associated with cognitive development during childhood, with most research conducted in areas with high F levels in community drinking water (CDW).

Method

Data from 316 to 248 mother-child pairs from the Infancia y Medio Ambiente (Childhood and Environment, INMA) birth cohort project with maternal urinary F level adjusted for creatinine (MUFcr) measurements in the first and third trimesters of pregnancy. Children’s cognitive domains and intelligence indexes were evaluated using the Bayley Scales (age of 1) and the McCarthy Scales (age of 4). Multiple linear regression analyses were carried out adjusting for a wide range of covariates related to the child, mother, family context and other potential neurotoxicants.

Results

No association was found between MUFcr levels and Bayley Mental Development Index score. Nevertheless, regarding the McCarthy scales, it was found that per unit (mg/g) of MUFcr across the whole pregnancy, scores in boys were greater for the verbal, performance, numeric and memory domains (B = 13.86, CI 95%: 3.91, 23.82), (B = 5.86, CI 95%: 0.32, 11.39), (B = 6.22, CI 95%: 0.65, 11.79) and (B = 11.63, CI 95%: 2.62, 20.63) respectively and for General Cognitive Index (B = 15.4, CI 95%: 6.32, 24.48). For girls there was not any cognitive score significantly associated with MUFcr, being the sex-F interactions significant (P interaction <0.05). Including other toxicants levels, quality of family context or deprivation index did not substantially change the results.

Conclusions

In boys, positive associations were observed between MUFcr and scores in cognitive domains at the age of 4. These findings are inconsistent with those from some previous studies and indicate the need for other population-based studies to confirm or overturn these results at low levels of F in CDW.