Prenatal exposure to higher levels of fluoride not only impairs cognitive development but also significantly increases the incidence of attention-deficit/hyperactivity disorder (ADHD) in children, new research shows.

“Our current study suggests that fluoride not only interferes with overall IQ or overall cognitive development but may also contribute to symptoms of ADHD,” lead investigator Morteza Bashash, PhD, Dalla Lana School of Public Health, University of Toronto, Canada, told Medscape Medical News.

This isn’t the first study linking fluoride to childhood ADHD or cognitive impairment. But, said Bashash, it is the first to find an increased incidence of ADHD with prenatal fluoride exposure.

“This work builds off of previous research I and my team published on this population demonstrating that higher levels of urine fluoride during pregnancy are associated with lower scores on tests of cognition and IQ in these school-age children,” he said.

The study was published online October 10 in Environment International.

Dose-Dependent Relationship

Previous animal studies as well as clinical studies have raised concerns over potential effects of fluoride exposure on neurobehavioral development, such as lower IQ and attention deficits, the investigators note.

To examine the association between prenatal exposure and symptoms associated with ADHD, the researchers analyzed data on 213 mother-child pairs from the Early Life Exposures to Environmental Toxicants (ELEMENT) birth cohort study. The study recruited pregnant women from 1994 to 2005 and continues to follow these women and children.

The research team used maternal urinary samples and child assessments of ADHD-like behaviors at ages 6 to 12 years.

They measured urinary fluoride levels adjusted for creatinine (MUFcr) in spot urine samples collected during pregnancy.

Child assessments consisted of both the Conners’ Rating Scales–Revised (CRS-R), which was completed by mothers, and the Conners’ Continuous Performance Test (CPT-II), which was administered to the children.

Data were adjusted for factors known to affect neurodevelopment, including lead exposure, smoking history, gestational age at birth, maternal marital status, age at delivery, and socioeconomic status.

The investigators found that the mean MUFcr was 0.85?mg/L (SD?=?0.33). The difference between the first and third quartiles, or interquartile range (IQR), was 0.46?mg/L.

Using gamma regression in multivariable adjusted models, the researchers found that a 0.5-mg/L higher MUFcr (about one IQR higher) corresponded with significantly higher scores on the CRS-R for DSM-IV Inattention (2.84 points; 95% confidence interval [CI], 0.84 – 4.84) and DSM-IV ADHD Total Index (2.38 points; 95% CI, 0.42 – 4.34).

*Original article online at https://www.medscape.com/viewarticle/903653

* Following the Media: The three new studies and the news articles that they generated are here

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