91�Թ�-led study finds link between 'ADHD-like symptoms' and high fluoride levels during pregnancy

Christopher.Sorensen — Wed, 10 Oct 2018 15:37:56 +0000

Christopher.Sorensen Wed, 10/10/2018 - 11:37

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The study analyzed data from 213 mother-child pairs in Mexico City (Photo by Lino Mirgeler/picture alliance via Getty Images)

Nicole Bodnar

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Global Lens

Breaking Research

Child Development

Dalla Lana School of Public Health

Fluoride

Higher levels of urinary fluoride during pregnancy are associated with more ADHD-like symptoms in school-age children as reported by parents, according to a new study by researchers at the 91�Թ� and other universities.

The findings, published today in Environment International, stem from the researchers’ analysis of data from 213 mother-child pairs in Mexico City that were part of the Early Life Exposures in Mexico to Environmental Toxicants project. The project recruited pregnant women from 1994 to 2005 and has continued to follow the women and their children ever since.

“Our findings are consistent with a growing body of evidence suggesting that the growing fetal nervous system may be negatively affected by higher levels of fluoride exposure,” said Morteza Bashash, the study’s lead author and a researcher at 91�Թ�’s Dalla Lana School of Public Health.

Tap water and dental products have been fluoridated in communities in Canada and the United States (as well as milk and table salt in some other countries) by varying amounts for more than 60 years to prevent cavities. In recent years, however, fierce debate over the safety of water fluoridation — particularly for children’s developing brains — has prompted researchers to explore the issue and provide evidence to inform national drinking water standards.

The study's research team — including experts from the 91�Թ�, York University, the National Institute of Public Health of Mexico, University of Michigan, Indiana University, the University of Washington and Harvard University — analyzed urine samples that had been obtained from mothers during pregnancy and from their children between six and 12 years of age to reconstruct personal measures of fluoride exposure for both mother and child.

The researchers then analyzed how levels of fluoride in urine related to the child’s performance on a variety of tests and questionnaires that measure inattention and hyperactivity, and provided overall scores related to ADHD, or Attention Deficit Hyperactivity Disorder. Analyses were adjusted for other factors known to impact neurodevelopment, such as gestational age at birth, birthweight, birth order, sex, maternal marital status, smoking history, age at delivery, education, socioeconomic status and lead exposure.

“Our findings show that children with elevated prenatal exposure to fluoride were more likely to show symptoms of ADHD as reported by parents,” said Bashash. “Prenatal fluoride exposure was more strongly associated with inattentive behaviours and cognitive problems, but not with hyperactivity,”

This work builds off of previous research the team published on this population demonstrating that higher levels of urine fluoride during pregnancy are associated with lower scores on tests of IQ and cognition in the school-age children.

ADHD is the most common psychiatric disorder diagnosed in childhood, affecting between five and nine per cent of all school-aged children.

“The symptoms of ADHD often persist into adulthood and can be impairing in daily life,” said Christine Till, an associate professor of psychology at York University and co-author on the study.

“If we can understand the reasons behind this association, we can then begin to develop preventive strategies to mitigate the risk,” said Till, who is also the principal investigator of another National Institutes of Health (NIH)-funded grant examining fluoride exposure in a large Canadian sample of pregnant women.

The study was funded by the National Institute of Environmental Health Sciences, part of the NIH.

Higher levels of fluoride in pregnant woman linked to lower intelligence in their children: 91�Թ� research

lanthierj — Tue, 19 Sep 2017 16:24:03 +0000

Higher levels of fluoride in pregnant woman linked to lower intelligence in their children: 91�Թ� research

lanthierj Tue, 09/19/2017 - 12:24

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Fierce debate over the safety of water fluoridation – particularly for children’s developing brains – has fuelled researchers to explore the issue and provide evidence to inform national drinking water standards (photo by Gullherme Jofill via Flickr)

Nicole Bodnar

Author legacy

Nicole Bodnar

Topic

Global Lens

Dalla Lana School of Public Health

Fluoride

Fluoride in the urine of pregnant women shows a correlation with lower measures of intelligence in their children, according to 91�Թ� researchers who conducted the first study of its kind and size to examine fluoride exposure and multiple states of neurodevelopment.

“Our study shows that the growing fetal nervous system may be adversely affected by higher levels of fluoride exposure,” said Dr. Howard Hu, the study’s principal investigator and professor of environmental health, epidemiology and global health at the Dalla Lana School of Public Health. “It also suggests that the prenatal nervous system may be more sensitive to fluoride compared to that of school-aged children.”

Tap water and dental products have been fluoridated in communities in Canada and the United States (as well as milk and table salt in some other countries) by varying amounts for more than 60 years to prevent cavities and improve bone health. In recent years, fierce debate over the safety of water fluoridation – particularly for children’s developing brains – has fuelled researchers to explore the issue and provide evidence to inform national drinking water standards.

There are some known side effects of fluoride. For example, dental defects like mild staining are common among those ingesting recommended levels of fluoride in the United States and Canada. Skeletal fluorosis – excessive accumulation of fluoride in the bones – is much less common and only observed at levels of fluoride in the water that are more than five to 10 times higher than those recommended.

“Relatively little is known, with confidence, about fluoride’s impact on neurodevelopment,” said Hu, whose research team included experts from 91�Թ�, National Institute of Public Health of Mexico, University of Michigan, McGill University, Indiana University, Mount Sinai School of Medicine and Harvard School of Public Health.

Dr. Howard Hu is the study’s principal investigator and professor of environmental health, epidemiology and global health at the Dalla Lana School of Public Health (photo courtesy of Dr. Howard Hu)

The study, “Prenatal Flu oride Exposure and Cognitive Outcomes in Children at 4 and 6-12 Years of Age in Mexico,” published today in Environmental Health Perspectives, analyzed data from 287 mother-child pairs in Mexico City that were part of the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) project, which recruited pregnant women from 1994 to 2005 and has continued to follow the women and their children ever since.

Read the study

The research team analyzed urine samples that had been taken from mothers during pregnancy and from their children between six and 12 years of age to reconstruct personal measures of fluoride exposure for both mother and child.

“This is significant because previous studies estimated exposures based on neighbourhood measurements of drinking water fluoride levels, which are indirect and much less precise measures of exposure. They also looked at children’s exposures instead of prenatal exposures or had much smaller sample sizes of subjects to study,” said Dr. Hu.

The researchers then analyzed how levels of fluoride in urine related to the children’s verbal, perceptual-performance, quantitative, memory, and motor abilities at age four and once more between the ages of six and 12. Analyses were adjusted for other factors known to impact neurodevelopment, such as gestational age at birth, birthweight, birth order, sex, maternal marital status, smoking history, age at delivery, IQ, education, socioeconomic status and lead exposure.

With regard to the study’s implications for populations in North America, researchers found that urinary fluoride levels in pregnant women were somewhat higher than, but within the general range of, urinary fluoride levels seen in non-pregnant general populations in Canada and the United States. However, in Dr. Hu’s opinion, the findings do not provide enough information to suggest there is no safe level of fluoride exposure.

“The potential risks associated with fluoride should be further studied, particularly among vulnerable populations such as pregnant women and children, and more research on fluoride’s impact on the developing brain is clearly needed.”

The National Institute of Environmental Health Sciences, part of the National Institutes of Health, funded this study.