Fluoride Exposure from Infant Formula and Child IQ in a Canadian Birth Cohort

Abstract

OPS 36: Health effects of dietary exposures, Room 210, Floor 2, August 27, 2019, 4:30 PM - 5:30 PM Background: Consumption of infant formula reconstituted with fluoridated water can lead to excessive intake of fluoride in infants. We examined the association between water fluoride concentration and intellectual ability (IQ) among preschool children who lived in fluoridated or non-fluoridated cities in Canada and were either formula-fed or breastfed during the first six months after birth. Methods: We measured water fluoride concentration using municipal water reports matched to the child’s birthdate to six-months of age. We restricted our analyses to 398 mother-child dyads enrolled in the Maternal-Infant Research on Environmental Chemicals (MIREC) cohort who reported drinking tap water. We evaluated Full Scale IQ (FSIQ) using the Wechsler Primary and Preschool Scale of Intelligence-III at 3 to 4 years. We used multiple linear regression analyses with an interaction to examine how the covariate-adjusted association between water fluoride concentration and FSIQ scores differs according to feeding status. In secondary analyses, we controlled for prenatal fluoride exposure. Results: Thirty-eight percent of mother-child dyads lived in communities supplied with fluoridated municipal water. An increase of 0.5 mg/L fluoride concentration (the difference between fluoridated and non-fluoridated region) corresponded to a drop of 4.4 FSIQ points (95% CI: -8.34, -0.46, p=.03) in the formula-fed group. In contrast, this relationship was not significant in the breastfed group (B=-1.34, 95% CI: -5.04, 2.38, p=.48). Controlling for prenatal fluoride exposure weakened the association between water fluoride concentration and FSIQ in the formula-fed group (B=-3.88, 95% CI = -8.12, 0.37, p=.07). Conclusions: The results, which indicate that fluoride concentration in drinking water was associated with lower FSIQ in children who were formula fed, underscore the need to reduce the use of fluoridated water to reconstitute formula during infancy.