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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Psychiatry | doi: 10.3389/fpsyt.2019.00524

Brain peak width of skeletonised mean diffusivity (PSMD) and cognitive function in later life.

Ian Deary1*, Stuart Ritchie2,  Susana Muñoz Maniega3, Simon Cox3,  Maria D. Valdés Hernández3,  Michelle Luciano4, John M. Starr5,  Joanna M. Wardlaw3 and  Mark Bastin3
  • 1Department of Psychology, School of Philosophy, Psychology and Language Sciences, University of Edinburgh, United Kingdom
  • 2King's College London, United Kingdom
  • 3University of Edinburgh, United Kingdom
  • 4Psychology, University of Edinburgh, United Kingdom
  • 5Department of Geriatric Medicine, College of Medicine and Veterinary Medicine, University of Edinburgh, United Kingdom

It is suggested that the brain’s peak width of skeletonised water mean diffusivity (PSMD) is a neuro-biomarker of processing speed, an important aspect of cognitive ageing. We tested whether PSMD is more strongly correlated with processing speed than with other cognitive domains, and more strongly than other structural brain MRI indices. Participants were 731 Lothian Birth Cohort 1936 members, mean age 73 years (SD=0.7); analytical sample was 656-680. Cognitive domains tested were: processing speed (5 tests), visuospatial (3), memory (3), and verbal (3). Brain-imaging variables included PSMD, white matter diffusion parameters and hyperintensity volumes, grey and white matter volumes, and perivascular spaces. PSMD was significantly associated with processing speed (-0.27), visuospatial ability (-0.23), memory ability (-0.17), and general cognitive ability (-0.25); comparable correlations were found with other brain-imaging measures. In a multivariable model with the other imaging variables, PSMD provided independent prediction of visuospatial ability and general cognitive ability. This incremental prediction, coupled with its ease to compute and possibly better tractability, might make PSMD a useful brain biomarker in studies of cognitive ageing.

Keywords: Ageing, Cognition, processing speed, structural MRI, diffusion MRI, white matter, PSMD

Received: 02 Apr 2019; Accepted: 03 Jul 2019.

Edited by:

Mohamad Habes, University of Pennsylvania, United States

Reviewed by:

Anil Man Tuladhar, Radboud University Nijmegen Medical Centre, Netherlands
Owen Williams, National Institute on Aging (NIA), United States  

Copyright: © 2019 Deary, Ritchie, Muñoz Maniega, Cox, Valdés Hernández, Luciano, Starr, Wardlaw and Bastin. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Ian Deary, Department of Psychology, School of Philosophy, Psychology and Language Sciences, University of Edinburgh, Edinburgh, EH8 9JZ, United Kingdom,