Associations of a toenail metal mixture with attention and memory in the Gulf long-term follow-up (GuLF) study

Joyce J. Lin, Department of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA. Electronic address: Jlin103@jhu.edu.
Jordan R. Kuiper, Department of Environmental and Occupational Health, The George Washington University Milken Institute School of Public Health, Washington, DC, USA.
Aisha S. Dickerson, Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
Jessie P. Buckley, Department of Epidemiology, University of North Carolina Gillings School of Global Public Health, Chapel Hill, NC, USA.
Heather E. Volk, Department of Mental Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
Diane S. Rohlman, Department of Occupational and Environmental Health, University of Iowa College of Public Health, Iowa City, IA, USA.
Kaitlyn G. Lawrence, Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA.
W Braxton Jackson, Social & Scientific Systems, Inc., Durham, NC, USA.
Dale P. Sandler, Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA.
Lawrence S. Engel, Department of Epidemiology, University of North Carolina Gillings School of Global Public Health, Chapel Hill, NC, USA; Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC, USA.
Ana M. Rule, Department of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.

Document Type

Journal Article

Publication Date

5-23-2024

Journal

The Science of the total environment

Volume

935

DOI

10.1016/j.scitotenv.2024.173387

Keywords

Metals; Mixtures; Neurobehavioral outcomes; Toenail biomarker

Abstract

BACKGROUND: Research on metal-associated neurodegeneration has largely focused on single metals. Since metal exposures typically co-occur as combinations of both toxic and essential elements, a mixtures framework is important for identifying risk and protective factors. This study examined associations between toenail levels of an eight-metal mixture and attention and memory in men living in US Gulf states. METHODS: We measured toenail concentrations of toxic (arsenic, chromium, lead, and mercury) and essential (copper, manganese, selenium, and zinc) metals in 413 non-smoking men (23-69 years, 46 % Black) from the Gulf Long-Term Follow-Up (GuLF) Study. Sustained attention and working memory were assessed at the time of toenail sample collection using the continuous performance test (CPT) and digit span test (DST), respectively. Associations between toenail metal concentrations and performance on neurobehavioral tests were characterized using co-pollutant adjusted general linear models and Bayesian Kernel Machine Regression. RESULTS: Adjusting for other metals, one interquartile range (IQR) increase in toenail chromium was associated with a 0.19 (95 % CI: -0.31, -0.07) point reduction in CPT D Prime score (poorer ability to discriminate test signals from noise). One IQR increase in toenail manganese was associated with a 0.20 (95 % CI, -0.41, 0.01) point reduction on the DST Reverse Count (fewer numbers recalled). Attention deficits were greater among Black participants compared to White participants for the same increase in toenail chromium concentrations. No evidence of synergistic interaction between metals or adverse effect of the overall metal mixture was observed for either outcome. CONCLUSIONS: Our findings support existing studies of manganese-related memory deficits and are some of the first to show chromium related attention deficits in adults. Longitudinal study of cognitive decline is needed to verify chromium findings. Research into social and chemical co-exposures is also needed to explain racial differences in metal-associated neurobehavioral deficits observed in this study.

Department

Environmental and Occupational Health

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