Browsing by Author "Hornung, Richard"

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    ADDENDUM: Critical windows of fluoride neurotoxicity in Canadian Children
    (Elsevier, 2022) Farmus, Linda; Till, Christine; Green, Rivka; Hornung, Richard; Martinez Mier, E. Angeles; Ayotte, Pierre; Muckle, Gina; Lanphear, Bruce P.; Flora, David B.; Dental Public Health and Dental Informatics, School of Dentistry
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    Critical windows of fluoride neurotoxicity in Canadian children
    (Elsevier, 2021) Farmus, Linda; Till, Christine; Green, Rivka; Hornung, Richard; Martinez Mier, E. Angeles; Ayotte, Pierre; Muckle, Gina; Lanphear, Bruce P.; Flora, David B.; Dental Public Health and Dental Informatics, School of Dentistry
    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.
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    Iodine Status Modifies the Association between Fluoride Exposure in Pregnancy and Preschool Boys' Intelligence
    (MDPI, 2022-07-16) Goodman, Carly V.; Hall, Meaghan; Green, Rivka; Chevrier, Jonathan; Ayotte, Pierre; Martinez-Mier, Esperanza Angeles; McGuckin, Taylor; Krzeczkowski, John; Flora, David; Hornung, Richard; Lanphear, Bruce; Till, Christine; Cariology, Operative Dentistry and Dental Public Health, School of Dentistry
    In animal studies, the combination of in utero fluoride exposure and low iodine has greater negative effects on offspring learning and memory than either alone, but this has not been studied in children. We evaluated whether the maternal urinary iodine concentration (MUIC) modifies the association between maternal urinary fluoride (MUF) and boys' and girls' intelligence. We used data from 366 mother-child dyads in the Maternal-Infant Research on Environmental Chemicals Study. We corrected trimester-specific MUF and MUIC for creatinine, and averaged them to yield our exposure variables (MUFCRE, mg/g; MUICCRE, µg/g). We assessed children's full-scale intelligence (FSIQ) at 3 to 4 years. Using multiple linear regression, we estimated a three-way interaction between MUFCRE, MUICCRE, and child sex on FSIQ, controlling for covariates. The MUICCRE by MUFCRE interaction was significant for boys (p = 0.042), but not girls (p = 0.190). For boys whose mothers had low iodine, a 0.5 mg/g increase in MUFCRE was associated with a 4.65-point lower FSIQ score (95% CI: -7.67, -1.62). For boys whose mothers had adequate iodine, a 0.5 mg/g increase in MUFCRE was associated with a 2.95-point lower FSIQ score (95% CI: -4.77, -1.13). These results suggest adequate iodine intake during pregnancy may minimize fluoride's neurotoxicity in boys.
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    Screening for brain aneurysm in the Familial Intracranial Aneurysm study: frequency and predictors of lesion detection
    (Journal of Neurosurgery Publishing Group (JNSPG), 2008-06) Brown, Robert D., Jr.; Huston, John, III; Hornung, Richard; Foroud, Tatiana; Kallmes, David F.; Kleindorfer, Dawn; Meissner, Irene; Woo, Daniel; Sauerbeck, Laura; Broderick, Joseph; Department of Medical & Molecular Genetics, School of Medicine,
    Object Approximately 20% of patients with an intracranial saccular aneurysm report a family history of intracranial aneurysm (IA) or subarachnoid hemorrhage. A better understanding of predictors of aneurysm detection in familial IA may allow more targeted aneurysm screening strategies. Methods The Familial Intracranial Aneurysm (FIA) study is a multicenter study, in which the primary objective is to define the susceptibility genes related to the formation of IA. First-degree relatives (FDRs) of those affected with IA are offered screening with magnetic resonance (MR) angiography if they were previously unaffected, are ≥ 30 years of age, and have a history of smoking and/or hypertension. Independent predictors of aneurysm detection on MR angiography were determined using the generalized estimating equation version of logistic regression. Results Among the first 303 patients screened with MR angiography, 58 (19.1%) had at least 1 IA, including 24% of women and 11.7% of men. Ten (17.2%) of 58 affected patients had multiple aneurysms. Independent predictors of aneurysm detection included female sex (odds ratio [OR] 2.46, p = 0.001), pack-years of cigarette smoking (OR 3.24 for 20 pack-years of cigarette smoking compared with never having smoked, p < 0.001), and duration of hypertension (OR 1.26 comparing those with 10 years of hypertension to those with no hypertension, p = 0.006). Conclusions In the FIA study, among the affected patients’ FDRs who are > 30 years of age, those who are women or who have a history of smoking or hypertension are at increased risk of suffering an IA and should be strongly considered for screening.