Abstract

Background: Fluoride is associated with IQ deficits during early brain development, but the period in which children are most vulnerable has not been established. We assessed sex-specific effects of fluoride on IQ across prenatal, infancy, and early childhood windows.

Methods: Repeated exposures from 596 mother-child pairs in the Maternal-Infant Research on Environmental Chemicals cohort were analyzed using GEE to explore associations between fluoride exposures and IQ after adjustment for covariates and multiple comparisons. Fluoride was measured in urine spot samples collected during pregnancy trimesters and when children were between 1.9 and 4.4 years. Infant fluoride exposure was estimated from water fluoride concentration and duration of formula-feeding over the first year of life. The Wechsler Preschool and Primary Scale of Intelligence-III was administered at 3 to 4 years.

Results: Among boys and girls, the association between fluoride and performance IQ (PIQ) significantly differed across exposure windows (p = .01). Among boys, prenatal exposure to fluoride was most strongly associated with adverse deficits on PIQ, B = -8.45 (95% CI: -12.90, -3.99), followed by infancy, B = -2.81 (95% CI: -6.59, 0.98), but not childhood, B = 0.20 (95% CI: -2.58, 2.99), respectively. Among girls, infancy exposure to fluoride was most strongly associated with adverse deficits on PIQ, B= -5.19 (95% CI: -8.84, -1.53), followed by prenatal and childhood exposures, B = -3.50 (95% CI: -9.51, 2.51), B = -2.05 (95% CI: -2.58, 2.99), respectively. Estimates for full-scale IQ were weaker but showed strongest effects for boys in the prenatal exposure period. Effects across all windows were nonsignificant among girls. We found no significant sex-specific associations between fluoride and verbal IQ.

Conclusion: Adverse associations between fluoride exposures and cognitive outcomes may depend on timing and biological sex, with the prenatal window potentially critical for boys, while infancy is potentially critical for girls.

This abstract was presented in SYMPOSIUM 20 at the virtual 32nd Conference of ISEE.

Author affiliations:

L. Farmus, York University, -Toronto, ON, CANADA

R. Green,  York University, -Toronto, ON, CANADA

C. Till, York University, -Toronto, ON, CANADA

R. Hornung, University of Cincinnati, Cincinatti, OH

E. Martinez Mier, Indiana University School of Dentistry, Indianapolis, IN

B. Lanphear, Simon Fraser University, Burnaby, BC, CANADA

D. Flora, York University, -Toronto, ON, CANADA

• Related Studies :

  • Fluoride Exposure and Concurrent Cognitive Outcomes in 7-15 Year Old Children from Mexico City, Mexico.

    BACKGROUND: Recent studies have reported an inverse association between fluoride exposure and IQ in children, but most were ecological in design. Few involved personal measures of exposure or adjusted for confounders. METHODS: This study utilized archived urine samples and data from offspring who participated in the Early Life Exposures in Mexico

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

    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

  • The importance of timing in fluoride-induced developmental neurotoxicity.

    Exposure to the fluoride ion can, in sufficient dose, induce neurotoxicity at any age, in both adults and children, but for fluoride-induced neurotoxicity to occur, in response to exposure to low doses of fluoride in the developing brain, the timing of the exposure is of importance. The evidence to date

  • Dietary Fluoride Intake during Pregnancy and Neurodevelopment in Toddlers: A Prospective Study in the PROGRESS Cohort.

    Highlights Mexican guidelines recommended a dietary reference intake for fluoride of 2.45 mg/d for adult and pregnant women. Mexico has a salt fluoridation program. High fluoride concentrations are neurotoxic. Median fluoride intake through foods and beverages was estimated to be 1.01 mg/d (0.73, 1.32) in a Mexican pregnancy cohort

  • WITHDRAWN: Co-exposure effects of arsenic and fluoride on intelligence and oxidative stress in school-aged children: a cohort study.

    This article has been withdrawn at the request of the editor. The Publisher apologizes for any inconvenience this may cause. as of November 6, 2020 Highlights Pioneer biomonitoring study on rural children to address As and F- co-exposure. High dental Fluorosis found in relation to urinary As and F- levels in

• Related FAN Content :

  • Annapolis: Water Fluoridation Linked to Death of Dialysis Patient

    EVENING CAPITAL (Annapolis, Maryland) November 29, 1979 Fluoride Linked to Death by Mary Ann Kryzankowicz Staff Writer Fluoride poisoning has been definitely linked to the death of a 65-year-old kidney dialysis patient who became ill during a blood cleaning process Nov 11. State Medical Examiner Dr. (illegible) Guard has ruled that Lawrence Blake, 65, of Arundel

  • Fluoridation of drinking water and chronic kidney disease: Absence of evidence is not evidence of absence

    A fairly substantial body of research indicates that patients with chronic renal insufficiency are at an increased risk of chronic fluoride toxicity. Patients with reduced glomerular filtration rates have a decreased ability to excrete fluoride in the urine. These patients may develop skeletal fluorosis even at 1 ppm fluoride in the drinking water.

  • Fluoride's Direct Effects on Brain: Animal Studies

    The possibility that fluoride ingestion may impair intelligence and other indices of neurological function is supported by a vast body of animal research, including over 40 studies that have investigated fluoride's effects on brain quality in animals. As discussed by the National Research Council, the studies have consistently demonstrated that fluoride, at widely varying concentrations, is toxic to the brain.

  • Fluoridated Water Causes Severe Dental Fluorosis in Children with Diabetes Insipidus

    This section on Diabetes includes: • Fluoride & Impaired Glucose Tolerance • Fluoride & Insulin • Fluoride Sensitivity Among Diabetics • Fluoridated Water Causes Severe Dental Fluorosis in Children with Diabetes Insipidus • NRC (2006): Fluoride’s Effect on Glucose Metabolism Excessive exposure to fluoride causes a defect of the tooth enamel known as dental fluorosis. In

  • Mayo Clinic: Fluoridation & Bone Disease in Renal Patients

    The available evidence suggests that some patients wtih long-term renal failure are being affected by drinking water with as little as 2 ppm fluoride. The finding of adverse effects in patients drinking water with 2 ppm of fluoride suggests that a few similar cases may be found in patients imbibing 1 ppm, especially if large volumes are consumed, or in heavy tea drinkers. The finding of adverse effects in patients drinking water with 2 ppm of fluoride suggests that a few similar cases may be found in patients imbibing 1 ppm, especially if large volumes are consumed, or in heavy tea drinkers and if fluoride is indeed the cause. It would seem prudent, therefore, to monitor the fluoride intake of patients with renal failure living in high fluoride areas.