Critical windows of fluoride neurotoxicity in Canadian children.

BACKGROUND: Fluoride has been associated with IQ deficits during early brain development, but the period in which children are most sensitive is unknown. OBJECTIVE: We assessed effects of fluoride on IQ scores across prenatal and postnatal exposure windows. METHODS: We used repeated exposures from 596 mother-child pairs in the Maternal-Infant Research on Environmental Chemicals pregnancy and birth cohort. Fluoride was measured in urine (mg/L) collected from women during pregnancy and in their children between 1.9 and 4.4 years; urinary fluoride was adjusted for specific gravity. We estimated infant fluoride exposure (mg/day) using water fluoride concentration and duration of formula-feeding over the first year of life. Intelligence was assessed at 3-4 years using the Wechsler Preschool and Primary Scale of Intelligence-III. We used generalized estimating equations to examine the associations between fluoride exposures and IQ, adjusting for covariates. We report results based on standardized exposures given their varying units of measurement. RESULTS: The association between fluoride and performance IQ (PIQ) significantly differed across prenatal, infancy, and childhood exposure windows collapsing across child sex (p = .001). The strongest association between fluoride and PIQ was during the prenatal window, B = -2.36, 95% CI: -3.63, -1.08; the association was also significant during infancy, B = -2.11, 95% CI: -3.45, -0.76, but weaker in childhood, B = -1.51, 95% CI: -2.90, -0.12. Within sex, the association between fluoride and PIQ significantly differed across the three exposure windows (boys: p = .01; girls: p = .01); among boys, the strongest association was during the prenatal window, B = -3.01, 95% CI: -4.60, -1.42, whereas among girls, the strongest association was during infancy, B = -2.71, 95% CI: -4.59, -0.83. Full-scale IQ estimates were weaker than PIQ estimates for every window. Fluoride was not significantly associated with Verbal IQ across any exposure window. CONCLUSION: Associations between fluoride exposure and PIQ differed based on timing of exposure. The prenatal window may be critical for boys, whereas infancy may be a critical window for girls.

The role of cognitive control and emotion regulation in predicting mental health problems in children with neurodevelopmental disorders.

BACKGROUND: Many youth with neurodevelopmental disorders (NDDs) experience mental health problems such as anxiety, depression or anger, and these are often associated with impairments of cognition and emotion regulation. The mechanisms that may be linking cognitive difficulties, emotion regulation and mental health are not known. AIMS: The current study examined whether adaptive and maladaptive (dysregulated) emotion regulation mediated the link between different cognitive control processes (working memory, inhibition and shifting) and internalizing/externalizing symptoms in children with NDDs. METHODS: Participants included 48 children (8-13 years of age) with one or more diagnoses of autism, attention deficit hyperactivity disorder, cerebral palsy and learning disability, who were enrolled in a larger study of cognitive behaviour therapy targeting emotion regulation. Multiple mediation analyses were implemented using the PROCESS macro. The mediation effects of adaptive and maladaptive emotion regulation were examined on the relationships between (1) working memory and internalizing/externalizing symptoms, (2) inhibition and internalizing/externalizing symptoms and (3) shifting and internalizing/externalizing symptoms. All data were collected prior to intervention, at baseline. RESULTS: Shifting, inhibitory control and working memory predicted increased emotion dysregulation, which functioned as a full mediator to both internalizing and externalizing problems in children with NDDs. CONCLUSIONS: In the presence of emotionally triggering situations, children with greater cognitive challenges experience greater maladaptive emotion regulation, which results in both internalizing and externalizing problems. For youth with NDDs, therapeutic plans that include strengthening of working memory, inhibition and shifting abilities in addition to emotion regulation skills training may be helpful in alleviating externalizing and internalizing behaviour.

Clinical and parental predictors of emotion regulation following cognitive behaviour therapy in children with autism.

LAY ABSTRACT: Children with autism commonly experience difficulty controlling their emotions. Although existing treatments are successful in teaching critical emotion regulation skills, not all children improve. It is important to identify the factors that influence treatment response to be able to reach more children. This study aimed to identify child and parent characteristics that predict treatment response in a 10-week cognitive behaviour therapy treatment for children with autism, 8-12 years of age, and their parents. We found that youth who started the treatment with higher verbal abilities, who were more anxious in social situations, and had parents who were more anxious, were more likely to improve in learning new emotion regulation skills. We also found that children who had more physical discomforts or complaints before starting the treatment were less likely to improve in their negative expressions of emotion. Our study suggests that it is important for clinicians to promote active involvement and learning by avoiding complex language and to use more visual materials to supplement the learning process, and make sure that sessions are sensitive to the individual needs of participants.

Fluoride exposure from infant formula and child IQ in a Canadian birth cohort.

BACKGROUND: Infant consumption of formula reconstituted with fluoridated water can lead to excessive fluoride intake. We examined the association between fluoride exposure in infancy and intellectual ability in children who lived in fluoridated or non-fluoridated cities in Canada. METHODS: We examined 398 mother-child dyads in the Maternal-Infant Research on Environmental Chemicals cohort who reported drinking tap water. We estimated water fluoride concentration using municipal water reports. We used linear regression to analyze the association between fluoride exposure and IQ scores, measured by the Wechsler Primary and Preschool Scale of Intelligence-III at 3-4 years. We examined whether feeding status (breast-fed versus formula-fed) modified the impact of water fluoride and if fluoride exposure during fetal development attenuated this effect. A second model estimated the association between fluoride intake from formula and child IQ. RESULTS: Thirty-eight percent of mother-child dyads lived in fluoridated communities. An increase of 0.5 mg/L in water fluoride concentration (approximately equaling the difference between fluoridated and non-fluoridated regions) corresponded to a 9.3- and 6.2-point decrement in Performance IQ among formula-fed (95% CI: -13.77, -4.76) and breast-fed children (95% CI: -10.45, -1.94). The association between water fluoride concentration and Performance IQ remained significant after controlling for fetal fluoride exposure among formula-fed (B = -7.93, 95% CI: -12.84, -3.01) and breastfed children (B = -6.30, 95% CI: -10.92, -1.68). A 0.5 mg increase in fluoride intake from infant formula corresponded to an 8.8-point decrement in Performance IQ (95% CI: -14.18, -3.34) and this association remained significant after controlling for fetal fluoride exposure (B = -7.62, 95% CI: -13.64, -1.60). CONCLUSIONS: Exposure to increasing levels of fluoride in tap water was associated with diminished non-verbal intellectual abilities; the effect was more pronounced among formula-fed children.