The association between simple reaction time variability and gait variability: The Tasmanian Study of Cognition and Gait.
Oshadi Jayakody, Monique Breslin, Richard Beare, Timothy P Siejka, Siddhanth Gujjari, Velandai K Srikanth, Helena M Blumen, Michele L Callisaya
Author Information
Oshadi Jayakody: Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia; Department of Medicine, Albert Einstein College of Medicine, Bronx, NY, USA.
Monique Breslin: Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia.
Richard Beare: Peninsula Clinical School, Central Clinical School, Monash University, Melbourne, VIC, Australia; Developmental Imaging, Murdoch Children's Research Institute, Royal Children's Hospital, Melbourne, VIC, Australia.
Timothy P Siejka: Alfred Health, Melbourne, VIC, Australia.
Siddhanth Gujjari: Monash Medical Centre, Monash Health, Melbourne, VIC, Australia.
Velandai K Srikanth: Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia; Peninsula Clinical School, Central Clinical School, Monash University, Melbourne, VIC, Australia.
Helena M Blumen: Department of Medicine, Albert Einstein College of Medicine, Bronx, NY, USA.
Michele L Callisaya: Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia; Peninsula Clinical School, Central Clinical School, Monash University, Melbourne, VIC, Australia. Electronic address: michele.callisaya@monash.edu.
INTRODUCTION: Greater double support time (DST) variability is associated with falls and memory decline. The underlying neurophysiological mechanisms of DST variability are poorly understood. Simple reaction time (SRT) variability, a measure of attention-processing speed is associated with falls and dementia and, may underlie greater DST variability. The aims of this study were to examine the association between SRT and DST variability and if SRT variability mediates the associations between poorer cognition/brain structure and DST variability. METHODS: Participants (n = 408) were community-dwelling older people without dementia (mean age 72.0 ± 7.0). DST variability was the standard deviation (SD) of DST, assessed with a walkway and averaged across steps of 6 walks. SRT variability was the SD of a button pressing task in response to a visual stimulus. Executive function and processing speed were assessed with neuropsychological tests. Magnetic Resonance Imaging was used to obtain cortical thickness (total and in frontal regions) and cerebral small vessel disease (cSVD). Multivariable linear regression models were used to examine the association between SRT and DST variability and if SRT variability mediated any associations of cognition/brain structure with DST variability. RESULTS: Greater SRT variability was associated with greater DST variability (p = 0.002). SRT variability partially mediated the association between poorer executive function and greater DST variability. Smaller mean thickness in orbitofrontal regions and greater cSVD burden were only associated with DST variability (p < 0.05), not with SRT variability (p > 0.05). CONCLUSIONS: Greater SRT variability, which may occur due to inefficient executive functioning, could be an underlying neurophysiological mechanism of greater DST variability.
