Manganese in teeth and neurodevelopment in young Mexican-American children

Introduction: Manganese (Mn) is an essential nutrient but higher exposure has been associated with poorer neurodevelopment in children. Methods: We measured Mn levels in prenatal (Mn-pre) (n=197) and postnatal (Mn-post) dentin (n=193) from children's shed teeth using laser ablation inductively coupled plasma mass spectroscopy and examined the relationship with children's scores on the Mental Development Index (MDI) and Psychomotor Development Index (PDI) on the Bayley Scales of Infant Development at 6, 12, and 24-months. We explored non-linear associations and interactions by sex, blood lead concentrations and maternal iron status during pregnancy. Results: A two-fold increase of Mn-post levels in dentin was associated with small decreases in MDI at 6-months and 12-months of age. We also observed a non-linear relationship between Mn-post levels and PDI at 6-months. We found effect modification by sex for Mn-post levels and neurodevelopment at 6-months with stronger effects among girls for both MDI (-1.5 points; 95% Confidence Interval (CI): -2.4, -0.6) and PDI (-1.8 points; 95% CI: -3.3, -0.3). Girls whose mothers had lower hemoglobin levels experienced larger decreases in MDI and PDI associated with Mn-pre levels than girls whose mothers had higher hemoglobin levels (p(interaction) =0.007 and 0.09, respectively). We did not observe interactions with blood lead concentrations or any relationships with neurodevelopment at 24-months. Conclusions: Using Mn measurements in tooth dentin, a novel biomarker that provides prenatal and early postnatal levels, we observed negative transient associations between postnatal Mn levels and early neurodevelopment with effect modification by sex and interactions with prenatal hemoglobin. (C) 2015 Elsevier Inc. All rights reserved.