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Domain-specific effects of prenatal fluoride exposure on child IQ at 4, 5, and 6-12 years

Full Title: Domain-specific effects of prenatal fluoride exposure on child IQ at 4, 5, and 6-12 years


Goodman C, Bashash M, Green R, Song P, Peterson KE, Schnaas Lourdes, Mercado-García A, Martínez-Medina S, Hernández-Avila M, Martinez-Mier A, Téllez-Rojo MM, Hu H, Till C


Environmental Research


Objective

Prenatal exposure to fluoride has been associated with adverse neurodevelopmental outcomes. However, the neuropsychological profile of fluoride's developmental neurotoxicity at low levels and the stability of this relationship across childhood has not been characterized. We investigated the longitudinal and domain specific effect of prenatal fluoride exposure on IQ among children ages 4, 5, and 6–12 years in the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) cohort.


Methods

We measured the average of maternal urinary fluoride at each trimester of pregnancy adjusted for creatinine (MUFCRE). Children were administered the McCarthy Scales of Children's Abilities at ages 4 (N = 386) and 5 (N = 308), and the Wechsler Abbreviated Scale of Intelligence at age 6–12 (N = 278). We used generalized estimating equation (GEE) models to estimate the population averaged effect of MUFCRE concentration on longitudinal General Cognitive Index (GCI)/Full-Scale IQ (FSIQ), Verbal IQ (VIQ), and Performance IQ (PIQ) scores (N = 348). We tested for possible interactions between MUFCRE and child sex as well as for MUFCRE and time point on children's IQ. All models controlled for relevant available covariates.


Results

The mean/median MUFCRE concentration was 0.90/0.83 mg/L (SD = 0.39; IQR, 0.64–1.11 mg/L). A 0.5 mg/L increase in MUFCRE predicted an average 2.12-point decrease in GCI/FSIQ (95% CI: −3.49, −0.75) and 2.63-point decrease in PIQ (95% CI: −3.87, −1.40). MUFCRE was marginally associated with VIQ across time (B = −1.29, 95% CI: −2.60, 0.01). No interactions between MUFCRE and child sex or MUFCRE and time were observed.


Conclusion

The negative association between prenatal fluoride exposure and longitudinal IQ was driven by decrements in non-verbal intelligence (i.e. PIQ), suggesting that visual-spatial and perceptual reasoning abilities may be more impacted by prenatal fluoride exposure as compared to verbal abilities.




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