Associations between early life exposure to manganese and developmental trajectories of executive functions

Abstract

BACKGROUND AND AIM: Manganese (Mn) is an essential nutrient at low doses, yet high levels can be neurotoxic. Executive functions (EF) are a set of cognitive abilities critical for goal directed behavior, which develop throughout childhood and adolescence. Only few studies examined the influence of early life exposures to Mn and developmental trajectories of EF. In this study, we investigated associations between early-life Mn exposure and changes in EF throughout adolescence. METHODS: Participants (N=154. 53% females) from the Public Health Impact of Metals Exposure (PHIME) study were included in this analysis. EF were measured using the Conners ADHD Scales (ages 11-14) and Brown ADD scales (ages 17-22). Prenatal, early postnatal and childhood Mn concentrations were measured in naturally shed deciduous teeth using laser ablation-inductively coupled plasma-mass spectrometry. We used general linear models to examine associations between prenatal, postnatal, and childhood dentine Mn with the change in attention (z-scored changes over time), adjusted for sex, and age. RESULTS:Childhood dentine Mn was significantly associated with developmental changes in attention (i.e., a negative slope; β = -0.98, p = 0.0008). No significant associations with prenatal and postnatal Mn were detected. CONCLUSIONS:These results indicate that Mn exposure during childhood may protect against increased attention problems, consistent with its nutrient properties. The flatter slope for postnatal and prenatal Mn and attention suggests an absence of protection. These finding support our hypotheses that trajectories are key to understanding the role of early-life metal exposures on EF development. KEYWORDS: Heavy metals, Children's environmental health, Neurodevelopmental outcomes,