title: Lower gray matter integrity is associated with greater lap time variation in high-functioning older adults.
abstract: BACKGROUND
  Lower integrity of cerebral gray matter is associated with higher gait variability. It is not known whether gray matter integrity is associated with higher lap time variation (LTV), a clinically accessible measure of gait variability, high levels of which have been associated with mortality. This study examines the cross-sectional association between gray matter mean diffusivity (MD) and LTV in community-dwelling older adults.
  
  
  METHODS
  Study participants consisted of 449 high-functioning adults aged 50 and older (56.8% female) in the Baltimore Longitudinal Study of Aging, free of overt neurological disease. The magnitude of MD in the gray matter, a measure of impaired tissue integrity, was assessed by diffusion tensor imaging in 16 regions of interest (ROIs) involved with executive function, sensorimotor function, and memory. LTV was assessed as variability in lap time based on individual trajectories over ten 40-m laps. Age, sex, height, and weight were covariates. The model additionally adjusted for mean lap time and health conditions that may affect LTV.
  
  
  RESULTS
  Higher levels of average MD across 16 ROIs were significantly associated with higher LTV after adjustment for covariates. Specifically, higher MD in the precuneus and the anterior and middle cingulate cortices was strongly associated with higher LTV, as compared to other ROIs. The association persisted after adjustment for mean lap time, hypertension, and diabetes.
  
  
  CONCLUSIONS
  Lower gray matter integrity in selected areas may underlie greater LTV in high-functioning community-dwelling older adults. Longitudinal studies are warranted to examine whether changes in gray matter integrity precede more variable gait.
authors.affiliation: Longitudinal Studies Section, Translational Gerontology Branch, National Institute on Aging, Baltimore, MD 21224, USA. Electronic address: qu.tian@nih.gov.
authors.forename: Qu
authors.initials: Q
authors.lastname: Tian
authors.affiliation: Laboratory of Behavioral Neuroscience, National Institute on Aging, Baltimore, MD 21224, USA.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Resnick
authors.affiliation: School of Engineering, Vanderbilt University, Nashville, TN 37212, USA.
authors.forename: Bennett A
authors.initials: BA
authors.lastname: Landman
authors.affiliation: School of Engineering, Vanderbilt University, Nashville, TN 37212, USA.
authors.forename: Yuankai
authors.initials: Y
authors.lastname: Huo
authors.affiliation: Laboratory of Behavioral Neuroscience, National Institute on Aging, Baltimore, MD 21224, USA.
authors.forename: Vijay K
authors.initials: VK
authors.lastname: Venkatraman
authors.affiliation: Laboratory of Behavioral Neuroscience, National Institute on Aging, Baltimore, MD 21224, USA.
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Gonzalez
authors.affiliation: Longitudinal Studies Section, Translational Gerontology Branch, National Institute on Aging, Baltimore, MD 21224, USA.
authors.forename: Eleanor M
authors.initials: EM
authors.lastname: Simonsick
authors.affiliation: Longitudinal Studies Section, Translational Gerontology Branch, National Institute on Aging, Baltimore, MD 21224, USA.
authors.forename: Michelle D
authors.initials: MD
authors.lastname: Shardell
authors.affiliation: Longitudinal Studies Section, Translational Gerontology Branch, National Institute on Aging, Baltimore, MD 21224, USA.
authors.forename: Luigi
authors.initials: L
authors.lastname: Ferrucci
authors.affiliation: Longitudinal Studies Section, Translational Gerontology Branch, National Institute on Aging, Baltimore, MD 21224, USA.
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Studenski
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000473:pathology*; D003430:Cross-Sectional Studies; D038524:Diffusion Magnetic Resonance Imaging; D005260:Female; D066128:Gray Matter / Q000473:pathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D016138:Walking / Q000706:statistics & numerical data*
keywords: Diffusion tensor imaging; Gray matter integrity; High-functioning older adults; Lap time variation; Mean diffusivity