title: Higher step length variability indicates lower gray matter integrity of selected regions in older adults.
abstract: Step length variability (SLV) increases with age in those without overt neurologic disease, is higher in neurologic patients, is associated with falls, and predicts dementia. Whether higher SLV in older adults without neurologic disease indicates presence of neurologic abnormalities is unknown. Our objective was to identify whether SLV in older adults without overt disease is associated with findings from multimodal neuroimaging. A well-characterized cohort of 265 adults (79-90 years) was concurrently assessed by gait mat, magnetic resonance imaging with diffusion tensor, and neurological exam. Linear regression models adjusted for gait speed, demographic, health, and functional covariates assessed associations of MRI measures (gray matter volume, white matter hyperintensity volume, mean diffusivity, fractional anisotropy) with SLV. Regional distribution of associations was assessed by sparse partial least squares analyses. Higher SLV (mean: 8.4, SD: 3.3) was significantly associated with older age, slower gait speed, and poorer executive function and also with lower gray matter integrity measured by mean diffusivity (standardized beta=0.16; p=0.02). Associations between SLV and gray matter integrity were strongest for the hippocampus and anterior cingulate gyrus (both β=0.18) as compared to other regions. Associations of SLV with other neuroimaging markers were not significant. Lower integrity of normal-appearing gray matter may underlie higher SLV in older adults. Our results highlighted the hippocampus and anterior cingulate gyrus, regions involved in memory and executive function. These findings support previous research indicating a role for cognitive function in motor control. Higher SLV may indicate focal neuropathology in those without diagnosed neurologic disease.
authors.affiliation: Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, USA. Electronic address: alr143@pitt.edu.
authors.forename: Andrea L
authors.initials: AL
authors.lastname: Rosso
authors.affiliation: Department of Biostatistics, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, USA.
authors.forename: Megan J
authors.initials: MJ
authors.lastname: Olson Hunt
authors.affiliation: Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, USA.
authors.forename: Mei
authors.initials: M
authors.lastname: Yang
authors.affiliation: Department of Physical Therapy, School of Health and Rehabilitation Sciences, University of Pittsburgh, Pittsburgh, USA.
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Brach
authors.affiliation: Laboratory of Epidemiology, Demography, and Biometry, Intramural Research Program, National Institute on Aging, Bethesda, USA.
authors.forename: Tamara B
authors.initials: TB
authors.lastname: Harris
authors.affiliation: Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, USA.
authors.forename: Anne B
authors.initials: AB
authors.lastname: Newman
authors.affiliation: Department of Preventive Medicine, University of Tennessee Health Science Center, Memphis, USA.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Satterfield
authors.affiliation: Division of Geriatric Medicine, School of Medicine, University of Pittsburgh, Pittsburgh, USA.
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Studenski
authors.affiliation: Department of Psychiatry, University of California, San Francisco, USA.
authors.forename: Kristine
authors.initials: K
authors.lastname: Yaffe
authors.affiliation: Department of Psychiatry, University of Pittsburgh, USA.
authors.forename: Howard J
authors.initials: HJ
authors.lastname: Aizenstein
authors.affiliation: Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, USA.
authors.forename: Caterina
authors.initials: C
authors.lastname: Rosano
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000473:pathology* / Q000502:physiology*; D016880:Anisotropy; D056324:Diffusion Tensor Imaging; D056344:Executive Function / Q000502:physiology; D005260:Female; D005684:Gait / Q000502:physiology*; D066128:Gray Matter / Q000473:pathology* / Q000502:physiology*; D006179:Gyrus Cinguli / Q000473:pathology* / Q000502:physiology; D006624:Hippocampus / Q000473:pathology* / Q000502:physiology; D006801:Humans; D016014:Linear Models; D008297:Male; D066127:White Matter / Q000473:pathology / Q000502:physiology
keywords: Aging; Brain; Diffusion tensor imaging; Gait disorders