Environmental manganese exposure and cognitive control in a South African population

Brad A. Racette, Department of Neurology, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8111, St. Louis, MO 63110, USA; School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown, 2193, South Africa. Electronic address: racetteb@wustl.edu.
Gill Nelson, School of Public Health, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown, 2193, South Africa. Electronic address: Gill.Nelson@wits.ac.za.
Wendy W. Dlamini, Department of Neurology, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8111, St. Louis, MO 63110, USA. Electronic address: wendy.dlamini@wustl.edu.
Tamara Hershey, Departments of Psychiatry and Radiology, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8225, St. Louis, MO, USA. Electronic address: tammy@wustl.edu.
Pradeep Prathibha, Department of Energy, Environmental, and Chemical Engineering, Washington University, Campus Box 1180, One Brookings Drive, St. Louis, MO 63130, USA. Electronic address: pradeep.prathibha@wustl.edu.
Jay R. Turner, Department of Energy, Environmental, and Chemical Engineering, Washington University, Campus Box 1180, One Brookings Drive, St. Louis, MO 63130, USA. Electronic address: jrturner@wustl.edu.
Harvey Checkoway, Herbert Wertheim School of Public Health and Department of Neurosciences, University of California, San Diego, 9500 Gilman Drive, # 0725, La Jolla, CA 92093-0725, USA. Electronic address: hcheckoway@ucsd.edu.
Lianne Sheppard, Departments of Biostatistics and Environmental and Occupational Health Sciences, University of Washington, Hans Rosling Center for Population Health, Box 351618, 3980 15th Avenue NE, Seattle, WA 98195-1618, USA. Electronic address: sheppard@uw.edu.
Susan Searles Nielsen, Department of Neurology, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8111, St. Louis, MO 63110, USA. Electronic address: snielsen@wustl.edu.

Document Type

Article

Abstract

OBJECTIVE: To characterize the association between environmental (residential air) manganese (Mn) exposure and cognitive performance, focusing on cognitive control, in a Black African population. METHODS: We administered the Go-No-Go, Digit Span, and Matrix Reasoning tests to population-based samples age ≥40 from a high Mn (smelter) exposed community, Meyerton (N = 629), and a demographically comparable low (background levels) non-exposed community, Ethembalethu, (N = 96) in Gauteng province, South Africa. We investigated the associations between community and performance on the cognitive tests, using linear regression. We adjusted a priori for age and sex, and examined the effect of adjustment for education, nonverbal IQ, smoking, and alcohol consumption. We measured airborne PM-Mn to confirm community exposure differences. RESULTS: Compared to Ethembalethu residents, Meyerton residents' test scores were lower (poorer) for all tests: 0.55 (95 % confidence interval [CI] 0.08, 1.03) lower scores for Matrix Reasoning, 0.34 (95 % CI -0.07, 0.75) lower for Digit Span, and 0.15 (95 % CI 0.09, 0.21) lower for Go-No-Go (high frequency discriminability index [probability]). The latter represented the most marked difference in terms of z-scores (0.50, 95 % CI 0.30, 0.71 standard deviations lower). The mean of the z-score of each of the three tests was also lower (0.34, 95 % CI 0.18, 0.50 standard deviations lower). These associations were similar in men and women, but attenuated with adjustment for education. Differences for Matrix Reasoning and Digit Span between the two communities were observed only among those who had lived in Meyerton ≥10 years, whereas for Go-No-Go, differences were also apparent among those who had lived in Meyerton <10 years. Mean PM-Mn at a long-term fixed site in Meyerton was 203 ng/m and 10 ng/m in Ethembalethu. CONCLUSION: Residence in a community near a high Mn emission source is associated with cognitive dysfunction, including aspects of cognitive control as assessed by the Go-No-Go test.

Medical Subject Headings

Cognition; Environmental Exposure (adverse effects); Female; Humans; Male; Manganese (adverse effects, analysis); Neuropsychological Tests; South Africa (epidemiology)

Publication Date

3-1-2022

Publication Title

Neurotoxicology

E-ISSN

1872-9711

Volume

89

First Page

31

Last Page

40

PubMed ID

34999155

Digital Object Identifier (DOI)

10.1016/j.neuro.2022.01.004

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