Executive functions in school-aged children exposed to airborne manganese: A multilevel analysis

Prenatal manganese biomarkers and operant test battery performance in Mexican children: Effect modification by child sex

BACKGROUND

Manganese (Mn) is essential to healthy neurodevelopment, but both Mn deficiency and over-exposure have been linked to prefrontal cortex (PFC) impairments, the brain region that regulates cognitive and neurobehavioral processes responsible for spatial memory, learning, motivation, and time perception. These processes facilitated by attention, inhibitory control, working memory, and cognitive flexibility are often sexually dimorphic and complex, driven by multiple interconnected neurologic and cognitive domains.

OBJECTIVE

We investigated the role of child sex as an effect modifier of the association between prenatal Mn exposure and performance in an operant testing battery (OTB) that assessed multiple cognitive and behavioral functional domains.

METHODS

Children (N = 575) aged 6-8 years completed five OTB tasks. Blood and urinary Mn measurements were collected from mothers in the 2nd and 3rd trimesters. Multiple regression models estimated the association between Mn biomarkers at each trimester with OTB performance while adjusting for socio-demographic covariates. Covariate-adjusted weighted quantile sum (WQS) regression models were used to estimate the association of a Mn multi-media biomarker (MMB) mixture with OTB performance. Interaction terms were used to estimate modification effect by child sex.

RESULTS

Higher blood Mn exposure was associated with better response rates (more motivation) on the progressive ratio task and higher overall accuracy on the delayed matching-to-sample task. In the WQS models, the MMB mixture was associated with better response rates (more motivation) on the progressive ratio task. Additionally, for the linear and WQS models, we observed a modification effect by child sex in the progressive ratio and delayed matching-to-sample tasks. Higher prenatal Mn biomarker levels were associated with improved task performance for girls and reduced performance in boys.

CONCLUSION

Higher prenatal blood Mn concentrations and the MMB mixture predicted improved performance on two of five operant tasks. Higher prenatal Mn concentrations regulated executive functions in children in a sexually dimorphic manner. Higher prenatal Mn exposure is associated with improved performance on spatial memory and motivation tasks in girls, suggesting that Mn's nutritional role is sexually dimorphic, and should be considered when making dietary and/or environmental intervention recommendations.

Physical activity mitigates the influence of blood cadmium on memory function: a cross-sectional analysis in US elderly population

Current evidence showed that heavy metal exposure including cadmium (Cd) exposure might contribute to memory function impairment in youth, while this association has not been extensively explored in senior groups. Complementary therapy like physical activity (PA) is proved to enhance memory; however, the combined effects of Cd exposure and PA are interesting issues worth investigating. Cross-sectional data from the National Health and Nutrition Examination Survey (NHANES) 2011-2014 were analyzed. Multivariable weighted linear regression model and restricted cubic splines analysis were used to examine the association between blood Cd, PA, and memory function. Ultimately, 1884 samples were analyzed, and the weighted participants were 98,350,183. Results showed that in the immediate and delayed recall tests, a negative association was found between blood Cd and scores for the fully adjusted model, while a positive association was detected with PA on memory test scores. In subgroup analysis, for the delayed recall test, in lower Cd exposure (Cd = Q1), stronger effect size was found in the moderate level PA group than the higher level PA group (moderate level PA group, β = 1.133, 95% CI: 0.330, 1.936; high level PA group, β = 0.203, 95% CI: - 0.314, 0.719), and this finding also existed in higher (Cd = Q4) exposure (moderate level PA group, β = 0.988, 95% CI: 0.267, 1.708; high level PA group, β = 0.830, 95% CI: 0.261, 1.400). Moreover, the non-linear relationship between Cd exposure and performance of CERAD test under different levels of PA was reported, and the moderate level PA group performed best from lower to higher blood Cd. According to our research, the benefit of PA did not always expand with the PA intensity increment under different Cd exposure. Performing an appropriate level of physical exercise could alleviate the memory decline under Cd exposure in the elder groups. Further biological investigations are warranted to verify these findings.