Do white matter hyperintensities mediate the association between brain iron deposition and cognitive abilities in older people?

M. Valdés Hernández, M. Allerhand, A. Glatz, L. Clayson, S. Muñoz Maniega, Alan J Gow, N. Royle, M. Bastin, J. Starr, I. Deary, J. Wardlaw

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    Abstract

    Background and purpose: Several studies have reported associations between brain iron deposits (IDs), white matter hyperintensities (WMHs) and cognitive ability in older individuals. Whether the association between brain IDs and cognitive abilities in older people is mediated by or independent of total brain tissue damage represented by WMHs visible on structural magnetic resonance imaging (MRI) was examined.

    Methods: Data from 676 community-dwelling individuals from the Lothian Birth Cohort 1936, with Mini-Mental State Examination scores >24, who underwent detailed cognitive testing and multimodal brain MRI at mean age 72.7 years were analysed. Brain IDs were assessed automatically following manual editing. WMHs were assessed semi-automatically. Brain microbleeds were visually counted. Structural equation modelling was used to test for mediation.

    Results: Overall, 72.8% of the sample had IDs with a median total volume of 0.040 ml (i.e. 0.004% of the total brain volume). The total volume of IDs, significantly and negatively associated with general cognitive function (standardized β = -0.17, P <0.01), was significantly and positively associated with WMH volume (std β = 0.13, P = 0.03). WMH volume had a significant negative association with general cognitive function, independent of IDs (std β = -0.13, P <0.01). The association between cognition and IDs in the brain stem (and minimally the total brain iron load) was partially and significantly mediated by WMH volume (P = 0.03).

    Conclusions: The negative association between brain IDs and cognitive ability in the elderly is partially mediated by WMHs, with this mediation mainly arising from the iron deposition load in the brain stem. IDs might be an indicator of small vessel disease that predisposes to white matter damage, affecting the neuronal networks underlying higher cognitive functioning.

    Original languageEnglish
    Pages (from-to)1202–1209
    Number of pages8
    JournalEuropean Journal of Neurology
    Volume23
    Issue number7
    Early online date20 Apr 2016
    DOIs
    Publication statusPublished - Jul 2016

    Keywords

    • MRI
    • Ageing
    • Cognition
    • Iron deposits
    • White matter hyperintensities

    ASJC Scopus subject areas

    • Clinical Neurology
    • Neurology

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  • Cite this

    Valdés Hernández, M., Allerhand, M., Glatz, A., Clayson, L., Muñoz Maniega, S., Gow, A. J., Royle, N., Bastin, M., Starr, J., Deary, I., & Wardlaw, J. (2016). Do white matter hyperintensities mediate the association between brain iron deposition and cognitive abilities in older people? European Journal of Neurology, 23(7), 1202–1209. https://doi.org/10.1111/ene.13006