Concurrent exposure to heavy metals and cognition in school-age children in Congo-Kinshasa: A complex overdue research agenda

Béatrice Koba Boraa, Ana Luiza Ramos-Crawfordb, Alla Sikorskiic, Michael Joseph Boivind,e, Didier Malamba Lezf, Dieudonné Mumba-Ngoyig,j, Abdon Mukalay Wa Mukalayh, Daniel Okitundu-Luwai, Desiré Tshala-Katumbayb,i,j,⁎


a Department of Neurology, School of Medicine, University of Lubumbashi, Lubumbashi, Democratic Republic of Congo
b Department of Neurology and School of Public Health, Oregon Health & Science University, Portland OR, USA
c Department of Statistics and Probability, Michigan State University, East Lansing, MI, USA
d Departments of Psychiatry and Neurology & Ophthalmology, Michigan State University, East Lansing MI, USA
e Department of Psychiatry, University of Michigan, Ann Arbor, MI, USA
f Department of Internal Medicine, School of Medicine, University of Lubumbashi, Lubumbashi, Democratic Republic of Congo
g Department of Tropical Medicine, University of Kinshasa, Kinshasa, Democratic Republic of Congo
h School of Public Health, University of Lubumbashi, Lubumbashi, Democratic Republic of Congo
i Department of Neurology, University of Kinshasa, Kinshasa, Democratic Republic of Congo
j National Institute of Biomedical Research (INRB), Kinshasa, Democratic Republic of Congo


A B S T R A C T

The impact of concurrent exposure to neurotoxic metals is a significant threat to brain function, mostly in contexts of multiple exposures as seen in the developing world. Ninety-five children (46 boys and 49 girls, 6 to 11-year old) from Congo-Kinshasa were assessed for cognition using the Kaufman Assessment Battery for
Children (2nd edition) and exposure to Cr, Cu, Zn, Co, Mn, As, Cd, Se, Hg, Fe, and Pb by inductively coupled plasma mass spectrometry (ICPMS) in serum and urine collections. Concentrations of elements were all above normal ranges except for Cd, Se and Hg. General linear mixed effects models were used to predict neurocognitive outcomes with variable selection methods including backward elimination, elastic net, or subsets identified based on subject matter expertise. After adjusting for sex, age, and SES, urinary Co > 5 μg/l was associated with poor simultaneous processing (memory) (p=0.0237). Higher excretion but normal concentration of Cd in serum was associated with better memory (p=0.03), planning (p=0.05), and overall performance scores (p < 0.01); thus appeared to be neuroprotective. However, higher excretion of Zn had negative influence on the overall performance scores (p=0.02). Predictive neurotoxicology is a challenging task in contexts of multiple and concurrent exposures. Urinary Co > 5 μg/l is a risk factor for poor neurodevelopmental outcomes in such contexts. The impact of heavy metals on cognition is dependent on concentrations of and interactions between toxic and essential elements.

Brain Research Bulletin
journal homepage: www.elsevier.com/locate/brainresbull

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