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. 2017 Sep 19;125(9):097017.
doi: 10.1289/EHP655.

Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6-12 Years of Age in Mexico

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Free PMC article

Prenatal Fluoride Exposure and Cognitive Outcomes in Children at 4 and 6-12 Years of Age in Mexico

Morteza Bashash et al. Environ Health Perspect. .
Free PMC article

Abstract

Background: Some evidence suggests that fluoride may be neurotoxic to children. Few of the epidemiologic studies have been longitudinal, had individual measures of fluoride exposure, addressed the impact of prenatal exposures or involved more than 100 participants.

Objective: Our aim was to estimate the association of prenatal exposure to fluoride with offspring neurocognitive development.

Methods: We studied participants from the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) project. An ion-selective electrode technique was used to measure fluoride in archived urine samples taken from mothers during pregnancy and from their children when 6-12 y old, adjusted for urinary creatinine and specific gravity, respectively. Child intelligence was measured by the General Cognitive Index (GCI) of the McCarthy Scales of Children's Abilities at age 4 and full scale intelligence quotient (IQ) from the Wechsler Abbreviated Scale of Intelligence (WASI) at age 6-12.

Results: We had complete data on 299 mother-child pairs, of whom 287 and 211 had data for the GCI and IQ analyses, respectively. Mean (SD) values for urinary fluoride in all of the mothers (n=299) and children with available urine samples (n=211) were 0.90 (0.35) mg/L and 0.82 (0.38) mg/L, respectively. In multivariate models we found that an increase in maternal urine fluoride of 0.5mg/L (approximately the IQR) predicted 3.15 (95% CI: -5.42, -0.87) and 2.50 (95% CI -4.12, -0.59) lower offspring GCI and IQ scores, respectively.

Conclusions: In this study, higher prenatal fluoride exposure, in the general range of exposures reported for other general population samples of pregnant women and nonpregnant adults, was associated with lower scores on tests of cognitive function in the offspring at age 4 and 6-12 y. https://doi.org/10.1289/EHP655.

Figures

Flowchart.
Figure 1.
Flowchart describing source of mother–offspring subject pairs, fluoride and cognition study. Cohort 2A was designed as an observational birth cohort of lead toxicodynamics during pregnancy, with mothers recruited early during pregnancy from 1997 to 2001. Cohort 3 was designed as a randomized double-blind placebo-controlled trial of calcium supplements, with mothers recruited early during pregnancy from 2001 to 2006. “Ca” denotes subjects who were randomized to the calcium supplement; “placebo” denotes subjects who were randomized to the placebo. GCI is the McCarthy Scales General Cognitive Index (administered at age 4 y). IQ is the Wechsler Abbreviated Intelligence Scales Intelligence Quotient (administered at age 6–12 y and age-adjusted).
Scatter plot with a regression line indicating McCarthy GCI at 48 months (y-axis) across concentration of prenatal M U F subscript cr in milligrams per liter (x-axis).
Figure 2.
Adjusted association of maternal creatinine-adjusted urinary fluoride (MUFcr) and General Cognitive Index (GCI) scores in children at age 4 y. Adjusted for gestational age, weight at birth, sex, parity (being the first child), age at outcome measurement, and maternal characteristics including smoking history (ever smoked vs. nonsmoker), marital status (married vs. others), age at delivery, IQ, education, and cohort (Cohort 3-Ca, Cohort 3-placebo and Cohort 2A). Shaded area is 95% confidence interval. Short vertical bars on the x-axis reflect the density of the urinary fluoride measures. Individual data points are individual observations, n=287.
Scatter plot with a regression line indicating WASI (IQ) at 6 to 12 years old (y-axis) across concentration of prenatal M U F subscript cr in milligrams per liter (x-axis). Scatter plot with a regression line indicating WASI (IQ) at 6 to 12 years old (y-axis) across concentration of prenatal M U F subscript cr in milligrams per liter (x-axis).
Figure 3.
(A) Adjusted association of maternal creatinine-adjusted urinary fluoride (MUFcr) and children’s IQ at age 6–12 y. Adjusted for gestational age, weight at birth, sex, parity (being the first child), age at outcome measurement, and maternal characteristics including smoking history (ever smoked vs. nonsmoker), marital status (married vs. others), age at delivery, IQ, education, and cohort (Cohort 3-Ca, Cohort 3-placebo and Cohort 2A). Short vertical bars on the x-axis reflect the density of the urinary fluoride measures. Individual data points are individual observation, n=211. (B) Association of maternal creatinine-adjusted urinary fluoride (MUFUcr) and children’s IQ at age 6–12 y, adjusted for specific gravity–adjusted child urinary fluoride (CUFsg). Adjusted for gestational age, weight at birth, sex, parity (being the first child), age and CUFsg at outcome measurement, and maternal characteristics including smoking history (ever smoked vs. nonsmoker), marital status (married vs. others), age at delivery, IQ, education. and cohort (Cohort 3-Ca, Cohort 3-placebo and Cohort 2A). Shaded area is 95% confidence interval. Short vertical bars on the x-axis reflect the density of the urinary fluoride measures. Individual data points are individual observation, n=189.

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