title: The effect of age and microstructural white matter integrity on lap time variation and fast-paced walking speed.
abstract: Macrostructural white matter damage (WMD) is associated with less uniform and slower walking in older adults. The effect of age and subclinical microstructural WM degeneration (a potentially earlier phase of WM ischemic damage) on walking patterns and speed is less clear. This study examines the effect of age on the associations of regional microstructural WM integrity with walking variability and speed, independent of macrostructural WMD. This study involved 493 participants (n = 51 young; n = 209 young-old; n = 233 old-old) from the Baltimore Longitudinal Study of Aging. All completed a 400-meter walk test and underwent a concurrent brain MRI with diffusion tensor imaging. Microstructural WM integrity was measured as fractional anisotropy (FA). Walking variability was measured as trend-adjusted variation in time over ten 40-meter laps (lap time variation, LTV). Fast-paced walking speed was assessed as mean lap time (MLT). Multiple linear regression models of FA predicting LTV and MLT were adjusted for age, sex, height, weight, and WM hyperintensities. Independent of WM hyperintensities, lower FA in the body of the corpus callosum was associated with higher LTV and longer MLT only in the young-old. Lower FA in superior longitudinal, inferior fronto-occipital, and uncinate fasciculi, the anterior limb of the internal capsule, and the anterior corona radiate was associated with longer MLT only in the young-old. While macrostructural WMD is known to predict more variable and slower walking in older adults, microstructural WM disruption is independently associated with more variable and slower fast-paced walking only in the young-old. Disrupted regional WM integrity may be a subclinical contributor to abnormal walking at an earlier phase of aging.
authors.affiliation: Longitudinal Studies Section, Translational Gerontology Branch, National Institute on Aging, 251 Bayview Blvd., Suite 100, Rm 04B316, Baltimore, 21224, Maryland. qu.tian@nih.gov.
authors.forename: Qu
authors.identifier: 0000-0003-2706-1439
authors.initials: Q
authors.lastname: Tian
authors.affiliation: Longitudinal Studies Section, Translational Gerontology Branch, National Institute on Aging, 251 Bayview Blvd., Suite 100, Rm 04B316, Baltimore, 21224, Maryland.
authors.forename: Luigi
authors.initials: L
authors.lastname: Ferrucci
authors.affiliation: Laboratory of Behavioral Neuroscience, National Institute on Aging, Baltimore, 21224, Maryland.
authors.forename: Susan M
authors.initials: SM
authors.lastname: Resnick
authors.affiliation: Longitudinal Studies Section, Translational Gerontology Branch, National Institute on Aging, 251 Bayview Blvd., Suite 100, Rm 04B316, Baltimore, 21224, Maryland.
authors.forename: Eleanor M
authors.initials: EM
authors.lastname: Simonsick
authors.affiliation: Longitudinal Studies Section, Translational Gerontology Branch, National Institute on Aging, 251 Bayview Blvd., Suite 100, Rm 04B316, Baltimore, 21224, Maryland.
authors.forename: Michelle D
authors.initials: MD
authors.lastname: Shardell
authors.affiliation: School of Engineering, Vanderbilt University, Nashville, 37212, Tennessee.
authors.forename: Bennett A
authors.initials: BA
authors.lastname: Landman
authors.affiliation: Laboratory of Behavioral Neuroscience, National Institute on Aging, Baltimore, 21224, Maryland.
authors.forename: Vijay K
authors.initials: VK
authors.lastname: Venkatraman
authors.affiliation: Laboratory of Behavioral Neuroscience, National Institute on Aging, Baltimore, 21224, Maryland.
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Gonzalez
authors.affiliation: Longitudinal Studies Section, Translational Gerontology Branch, National Institute on Aging, 251 Bayview Blvd., Suite 100, Rm 04B316, Baltimore, 21224, Maryland.
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Studenski
mesh_terms: D000368:Aged; D000375:Aging / Q000502:physiology; D015142:Baltimore / Q000453:epidemiology; D001921:Brain / Q000000981:diagnostic imaging*; D056324:Diffusion Tensor Imaging; D005080:Exercise Test; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D000072797:Walking Speed; D066127:White Matter / Q000000981:diagnostic imaging*
keywords: Diffusion tensor imaging; Fast-paced walking speed; Lap time variation; White matter integrity