• Qu Tian, Eleanor M Simonsick, Susan M Resnick, Michelle D Shardell, Luigi Ferrucci, and Stephanie A Studenski.
• National Institute on Aging, NIH-Translational Gerontology Branch, Baltimore, MD, USA.
• Age Ageing. 2015 Sep 1; 44 (5): 796-800.

Backgroundpoor cognitive and motor performance predicts neurological dysfunction. Variable performance may be a subclinical indicator of emerging neurological problems.Objectiveexamine the cross-sectional association between a clinically accessible measure of variable walking and executive function.Methodsolder adults aged 60 or older from the Baltimore Longitudinal Study of Aging (n = 811) with data on the 400-m walk test and cognition. Based on ten 40-m laps, we calculated mean lap time (MLT) and variation in time across ten 40-m laps (lap time variation, LTV). Executive function tests assessed attention and short-term memory (digit span forward and backward), psychomotor speed [Trail Making Test (TMT) part A] and multicomponent tasks requiring cognitive flexibility [TMT part B, part B-A (Delta TMT) and digit symbol substitution test (DSST)]. Multivariate linear regression analysis examined the cross-sectional association between LTV and executive function, adjusted for MLT, age, sex and education, as well as the LTV × MLT interaction.Resultsthe LTV was univariately associated with all executive function tests except digit span (P < 0.001); after adjustment, the association with TMT part A remained (standardised β = 0.142, P = 0.002). There was an interaction between MLT and LTV; among fast walkers, greater LTV was associated with a greater Delta TMT (β for LTV × MLT = -1.121, P = 0.016) after adjustment.Conclusionat any walking speed, greater LTV is associated with psychomotor slowing. Among persons with faster walking speed, variation is associated with worse performance on a complex measure of cognitive flexibility. A simple measure of variability in walking time is independently associated with psychomotor slowing.© The Author 2015. Published by Oxford University Press on behalf of the British Geriatrics Society. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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