![]() Consistent with this, several studies indicate that IIV RT is greater in older age and in a variety of neuropathological conditions of old age including mild cognitive impairment, dementia and Parkinson’s disease. ![]() IIV RT has received considerable attention as a useful indicator of neurobiological disturbance. Such variability in performance is often measured by the trial-to-trial within-person variation in reaction times (RT) on a single cognitive task and is known as intraindividual reaction time variability (IIV RT). In addition to average performance level, there is an increasing focus in ageing research on intraindividual variability or inconsistency in cognitive performance. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: The authors have declared that no competing interests exist. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.ĭata Availability: Data may be available to interested researchers upon request to the Sydney Memory and Ageing Study (MAS) Governance Committee (via email: This is required because of the conditions of the MAS ethics approval and the consent forms which only allows data to be passed onto third parties following review and approval by the study governance committee.įunding: Funded by National Health and Medical Research Council of Australia Program Grant (grant number 350833) (HB PS), National Health and Medical Research Council of Australia Early Career Fellowship (grant number 123148) (NK), and Dementia Collaborative Research Centre (NK). Received: FebruAccepted: JPublished: August 9, 2017Ĭopyright: © 2017 Kochan et al. Ginsberg, Nathan S Kline Institute, UNITED STATES Our findings suggest that greater IIV RT uniquely predicts shorter time to death and that lower global cognition and prodromal dementia in older individuals do not explain this relationship.Ĭitation: Kochan NA, Bunce D, Pont S, Crawford JD, Brodaty H, Sachdev PS (2017) Is intraindividual reaction time variability an independent cognitive predictor of mortality in old age? Findings from the Sydney Memory and Ageing Study. After excluding incident dementia cases, the association of IIV RT with mortality changed very little. Greater IIV RT but not mean RT significantly predicted survival time after adjusting for age, sex, global cognition score, cardiovascular risk index and apolipoprotein ɛ4 status. Cox proportional hazards models estimated the association of IIV RT and mean RT with survival time over 8 years during which 191 (22.2%) participants died. Consensus dementia diagnoses were made by an expert panel of clinicians using clinical criteria, and mortality data were obtained from a state registry. ![]() Composite RT measures were derived from the two tasks-the mean RT and the IIV RT measure computed from the intraindividual standard deviation of the RTs (with age and time-on-task effects partialled out). Participants completed two computerised reaction time (RT) tasks (76 trials in total) at baseline, and comprehensive medical and neuropsychological assessments every 2 years. This study investigated the association of IIV RT and all-cause mortality while accounting for cognitive level, incident dementia and biomedical risk factors in 861 participants aged 70–90 from the Sydney Memory and Ageing Study. The extent to which IIV RT is an independent predictor of mortality, however, is unclear. Intraindividual variability of reaction time (IIV RT), a proposed cognitive marker of neurobiological disturbance, increases in old age, and has been associated with dementia and mortality. ![]()
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