ORCID Profile
0000-0001-6206-1069
Current Organisation
University of Tasmania
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Publisher: S. Karger AG
Date: 2012
DOI: 10.1159/000339295
Abstract: b i Background: /i /b Research on the relationship between vestibular function and falls in older people is sparse. The perception of the postural vertical (PPV) provides an indicator measure of vestibular (otolith) function in the absence of visual input and diminished somatosensory feedback. b i Objective: /i /b This study examined whether impaired PPV is associated with falls in this group. b i Methods: /i /b One hundred and ninety-five people aged 70 plus years stood blindfolded on a motorised platform that could be tilted in the roll plane and attempted to adjust it so that their bodies were aligned to the vertical. Somatosensory feedback was minimised as the base and vertical support surfaces on the tilting platform were covered in thick soft foam rubber. PPV error from true vertical and PPV variability (°) were calculated. Participants also underwent an assessment of distal tactile sensitivity and the physiological profile assessment (PPA) fallers were defined as those who had one or more falls during a prospective 12-month follow-up period. b i Results: /i /b Eighty-eight participants (45%) reported falling in the follow-up year. Increased PPV error and variability were correlated with increased lateral sway in a condition of absent visual input and reduced foot somatosensory feedback (eyes closed/foam r range = 0.16–0.20, p 0.05) and with composite PPA fall risk scores (r range = 0.22–0.26, p 0.05). PPV variability was a significant and independent predictor of falls after adjusting for the composite PPA scores, age and gender [adjusted RR = 1.42 (1.01–1.98)]. b i Conclusions: /i /b Older people with increased PPV variability are at increased risk of falls. These findings indicate that assessment of PPV may augment fall risk assessments in older people.
Publisher: Elsevier BV
Date: 04-2012
Publisher: Oxford University Press (OUP)
Date: 10-2008
DOI: 10.1093/GERONA/63.10.1063
Abstract: Studies comparing the effects of spatial and nonspatial secondary tasks on balance have produced conflicting results. However, in most of these studies the difficulty levels of the secondary tasks have not been matched. In this study, we compared the effects of carefully matched visuospatial (VS) and nonspatial (NS) secondary tasks on choice stepping reaction time (CSRT). Forty-one older people (mean age 78.8 years) completed a CSRT test under five conditions: (i) no secondary task (ii) an easy NS counting backward task (iii) a difficult NS counting back task (iv) an easy VS memory task and (v) a difficult VS memory task. Response times and secondary task errors were measured for each condition. Participants also gave difficulty ratings for each secondary task. The difficult tasks were rated significantly more difficult than the easy tasks in both VS and NS conditions, and cognitive task errors were moderately correlated with perceived difficulty. A repeated-measure analysis of variance with planned contrasts revealed a significant effect of task type, with the VS condition slowing CSRT more than the NS condition. There was also a significant task difficulty effect with the more difficult tasks increasing CSRT. The findings suggest that VS cognitive tasks affect CSRT more so than do NS tasks. The visuospatial sketchpad appears to be specifically utilized for carrying out motor tasks necessary for preserving balance. Practical implications are that tasks that require visuospatial attention and memory may adversely influence balance control in older people.
Publisher: Wiley
Date: 14-02-2014
DOI: 10.1002/MDS.25831
Publisher: Elsevier BV
Date: 07-2021
Publisher: Journal of Neurosurgery Publishing Group (JNSPG)
Date: 06-2012
Abstract: The effect of deep brain stimulation (DBS) for Parkinson disease (PD) on balance is unclear. The goal of this study was to investigate how automatic postural responses (APRs) were affected in patients randomized to either subthalamic nucleus (STN) or globus pallidus internus (GPi) surgery. The authors tested 24 patients with PD who underwent bilateral DBS, 9 control patients with PD who did not undergo DBS, and 17 age-matched control volunteers. The electrode placement site was randomized and blinded to the patients and to the experimenters. Kinematic, kinetic, and electromyographic recordings of postural responses to backward disequilibrium via forward translations of the standing surface were recorded in the week prior to surgery while the patients were off (OFF) and on (ON) antiparkinsonian medication (levodopa), and then 6 months after surgery in 4 conditions: 1) off medication with DBS switched off (OFF/OFF) 2) off medication with DBS on (DBS) 3) on medication with DBS off (DOPA) and 4) with both medication and DBS on (DBS+DOPA). Stability of the automatic postural response (APR) was measured as the difference between the displacement of the center of pressure and the projected location of the center of body mass. Patients with PD had worse APR stability than controls. Turning the DBS on at either site improved APR stability compared with the postoperative OFF condition by lengthening the tibialis response, whereas medication did not show an appreciable effect. The STN group had worse APR stability in their best functional state (DBS+DOPA) 6 months after the DBS procedure compared with their best functional state (ON levodopa) before the DBS procedure. In contrast, the GPi group and the PD control group showed no change over 6 months. The APR stability impairment in the STN group was associated with smaller tibialis response litudes, but there was no change in response latency or coactivation with gastrocnemius. Turning the DBS current on improved APR stability for both STN and GPi sites. However, there was a detrimental DBS procedural effect for the STN group, and this effect was greater than the benefit of the stimulating current, making overall APR stability functionally worse after surgery for the STN group.
Publisher: Wiley
Date: 15-02-2011
Publisher: Wiley
Date: 30-07-2023
DOI: 10.1002/ALZ.13401
Abstract: Finding low‐cost methods to detect early‐stage Alzheimer's disease (AD) is a research priority for neuroprotective drug development. Presymptomatic Alzheimer's is associated with gait impairment but hand motor tests, which are more accessible, have hardly been investigated. This study evaluated how home‐based Tasmanian (TAS) Test keyboard tapping tests predict episodic memory performance. 1169 community participants (65.8 ± 7.4 years old 73% female) without cognitive symptoms completed online single‐key and alternate‐key tapping tests and episodic memory, working memory, and executive function cognitive tests. All single‐key ( R 2 adj = 8.8%, ΔAIC = 5.2) and alternate‐key ( R 2 adj = 9.1%, ΔAIC = 8.8) motor features predicted episodic memory performance relative to demographic and mood confounders only ( R 2 adj = 8.1%). No tapping features improved estimation of working memory. Brief self‐administered online hand movement tests predict asymptomatic episodic memory impairment. This provides a potential low‐cost home‐based method for stratification of enriched cohorts. We devised two brief online keyboard tapping tests to assess hand motor function. 1169 cognitively asymptomatic adults completed motor‐ and cognitive tests online. Impaired hand motor function predicted reduced episodic memory performance. This brief self‐administered test may aid stratification of community cohorts.
Publisher: American Physiological Society
Date: 08-2016
Abstract: There is evidence that postural instability associated with Parkinson's disease (PD) is not adequately improved by levodopa, implying involvement of nondopaminergic pathways. However, the mechanisms contributing to postural instability have yet to be fully identified and tested for their levodopa responsiveness. In this report we investigate balance processes that resist external forces to the body when standing. These include in-place responses and the transition to protective stepping. Forward and backward shoulder pulls were delivered using two force-feedback-controlled motors and were randomized for direction, magnitude, and onset. Sixteen patients with PD were tested OFF and ON levodopa, and 16 healthy controls were tested twice. Response behavior was quantified from 3-dimensional ground reaction forces and kinematic measurements of body segments and total body center-of-mass (CoM) motion. In-place responses resisting the pull were significantly smaller in PD as reflected in reduced horizontal anteroposterior ground reaction force and increased CoM displacement. Ankle, knee, and hip moments contributing to this resistance were smaller in PD, with the knee extensor moment to backward pulls being the most affected. The threshold force needed to evoke a step was also smaller for PD in the forward direction. Protective steps evoked by suprathreshold pulls showed deficits in PD in the backward direction, with steps being shorter and more steps being required to arrest the body. Levodopa administration had no significant effect on either in-place or protective stepping deficits. We conclude that processes employed to maintain balance in the face of external forces show impairment in PD consistent with disruption to nondopaminergic systems.
Publisher: Oxford University Press (OUP)
Date: 13-11-2009
Abstract: to compare the effects of two different exercise programmes after hip fracture. assessor-blinded randomised controlled trial. hospital rehabilitation units, with continued intervention at home. 160 people with surgical fixation for hip fracture transferred to inpatient rehabilitation. in addition to other rehabilitation strategies, the intervention group received a higher dose (60 min/day) exercise programme conducted whilst standing and the control group received a lower dose exercise programme (30 min/day) primarily conducted whilst seated/supine. The primary outcome measures were knee extensor muscle strength in the fractured leg and walking speed, measured at 4 and 16 weeks. 150 participants (94% of those recruited) completed the trial. There were no differences between the groups for the two primary outcome measures. Post hoc analyses revealed increased walking speed among those in the higher dose, weight-bearing exercise group with cognitive impairment at 4 and 16 weeks. there was no benefit (or harm) due to the higher dose, weight-bearing exercise programme with respect to the primary outcome measures. However, people with hip fracture and cognitive impairment gained greater benefit from the higher dose programme than from the lower dose programme.
Publisher: Center for Open Science
Date: 08-2022
Abstract: Response-selective stopping requires cancellation of only one component of a multicomponent action. While research has investigated how delays to the continuing action components (‘stopping interference’) can be attenuated by way of contextual cues of the specific stopping demands (‘foreknowledge’), little is known of the underlying neural mechanisms. Twenty-seven healthy young adults undertook a multicomponent stop-signal task. On 2/3rd of trials, participants responded to an imperative (go) stimulus (IS) with simultaneous button presses using their left and right index fingers. On the remaining 1/3rd of trials, the IS was followed by a stop-signal requiring cancellation of only the left, or right, response. To manipulate foreknowledge of stopping demands, a cue preceded the IS that informed participants which hand might be required to stop (proactive) or provided no such information (reactive). Transcranial magnetic stimulation (TMS) assessed corticospinal excitability (CSE) as well as short- and long-interval interhemispheric inhibition (SIHI, LIHI) between the primary motor cortices. Proactive cues reduced, but did not eliminate, stopping interference relative to the reactive condition. Relative to TMS measures at cue onset, decreases in CSE (both hands and both cue conditions) and LIHI (both hands, proactive condition only) were observed during movement preparation. During movement cancellation, LIHI reduction in the continuing hand was greater than that in the stopping hand, and greater than LIHI reductions in both hands during execution of multicomponent responses. Our results indicate that foreknowledge attenuates stopping interference and provide evidence for a novel role of LIHI, mediated via prefrontal regions, in facilitating continuing action components.
Publisher: Elsevier BV
Date: 02-2004
DOI: 10.1016/J.APMR.2003.06.015
Abstract: To evaluate, in older people with diabetic peripheral neuropathy (DPN) and in age-matched controls, acceleration patterns of the head and pelvis when walking to determine the effect of lower-limb sensory loss on walking stability. Case-control study. Falls and balance laboratory in Australia. Thirty persons with diabetes mellitus (age range, 55-91 y) and 30 age-matched controls. Acceleration patterns of the head and pelvis were measured while participants walked on a level surface and an irregular walkway. Participants also underwent tests of vision, sensation, strength, reaction time, and balance. Temporospatial gait parameters and variables derived from acceleration signals. Participants with DPN had reduced walking speed, cadence, and step length, and less rhythmic acceleration patterns at the head and pelvis compared with controls. These differences were particularly evident when participants walked on the irregular surface. Participants with DPN also had impaired peripheral sensation, reaction time, and balance. Older people with DPN have an impaired ability to stabilize their body when walking on irregular surfaces, even if they adopt a more conservative gait pattern. These results provide further insights into the role of peripheral sensory input in the control of gait stability, and suggest possible mechanisms underlying the increased risk of falling in older people with diabetic neuropathy.
Publisher: Springer Science and Business Media LLC
Date: 27-07-2013
Publisher: Oxford University Press (OUP)
Date: 12-02-2010
Abstract: Trips are the largest contributor to falls in older people, yet little is known about the underlying physiological mechanisms for safe obstacle negotiation. The aims of the study were to determine (i) the effect of a secondary visual task on obstacle contacts when older people negotiated an obstacle course and (ii) physiological factors associated with obstacle contacts. Thirty community-living adults aged 65 years and older walked along a 14.5-m walkway containing 21 obstacles with and without a secondary task. The secondary task required participants to call out a series of letters presented in front of them at head height and the suit of a playing card framed on the sidewall. Obstacle contacts, secondary task errors, eye peak-to-peak pitch litude and head peak-to-peak pitch litude (PA-H), and head angle in pitch were measured. Participants also completed assessments of sensorimotor function and balance. Compared with the obstacle-only trials, participants performed the dual-task trials more slowly (p < .001), contacted more obstacles (p = .032), showed greater PA-H (p < .001), and an extended head position (p < .001). Most participants also made secondary task errors. Regression analysis revealed that depth perception was the only significant determinant of obstacle contacts (explaining 20.6% of the variance) in the obstacle-only task and that depth perception and PA-H were independent and significant determinants of obstacle contacts (explaining 42.3% of the variance) in the dual task. The findings demonstrate the importance of depth perception and head movement for safe negotiation of obstacles in older people and suggest that depth perception in particular should form part of fall risk assessments.
Publisher: Elsevier BV
Date: 2024
Publisher: American Physiological Society
Date: 09-2015
Abstract: The effects of deep brain stimulation (DBS) on balance in people with Parkinson's disease (PD) are not well established. This study examined whether DBS randomized to the subthalamic nucleus (STN n = 11) or globus pallidus interna (GPi n = 10) improved compensatory stepping to recover balance after a perturbation. The standing surface translated backward, forcing subjects to take compensatory steps forward. Kinematic and kinetic responses were recorded. PD-DBS subjects were tested off and on their levodopa medication before bilateral DBS surgery and retested 6 mo later off and on DBS, combined with off and on levodopa medication. Responses were compared with PD-control subjects ( n = 8) tested over the same timescale and 17 healthy control subjects. Neither DBS nor levodopa improved the stepping response. Compensatory stepping in the best-treated state after surgery (DBS+DOPA) was similar to the best-treated state before surgery (DOPA) for the PD-GPi group and the PD-control group. For the PD-STN group, there were more lateral weight shifts, a delayed foot-off, and a greater number of steps required to recover balance in DBS+DOPA after surgery compared with DOPA before surgery. Within the STN group five subjects who did not fall during the experiment before surgery fell at least once after surgery, whereas the number of falls in the GPi and PD-control groups were unchanged. DBS did not improve the compensatory step response needed to recover from balance perturbations in the GPi group and caused delays in the preparation phase of the step in the STN group.
Publisher: MDPI AG
Date: 05-07-2022
DOI: 10.3390/GERIATRICS7040072
Abstract: Figure drawing tasks are commonly used standalone or as part of broader screening tests to detect cognitive impairment. Only one study has compared the classification accuracy of three common drawing tasks—overlapping infinity loops, wire cube, and the clock drawing task (CDT)—in mild cognitive impairment (MCI) and dementia, but age and education, which impact performance, were not accounted for. We replicated the research, adjusting for age and education and, for the first time, assessed subjective cognitive decline (SCD) too. Participants were recruited from the Tasmanian ISLAND Cognitive Clinic and healthy controls from a community s le. All participants completed the three figure drawing tasks. The clinic patients were categorised according to interdisciplinary consensus diagnosis. Binomial logistic regression and area under ROC curves (AUC) were calculated to determine the discriminatory ability of each drawing task. Overall, 112 adults were recruited 51 had normal cognition (NC), 21 SCD, 24 MCI, and 16 had dementia. The infinity loops test did not discriminate any of the groups, casting some doubt on its usefulness. The wire cube discriminated NC from dementia (AUC 0.7 p 0.05). The CDT discriminated NC from dementia (AUC 0.77 p 0.01), NC from cognitive impairment (dementia + MCI AUC 0.59 p 0.05), and MCI from dementia (AUC 0.76 p 0.01). None of the tests discriminated NC from MCI or NC from SCD. The CDT was the most discriminatory test, followed by the wire cube. This may help guide clinicians who often choose just one figure drawing task due to time constraints or patient fatigue.
Publisher: Elsevier BV
Date: 10-2020
Publisher: Wiley
Date: 28-03-2020
DOI: 10.1113/JP275436
Publisher: Springer Science and Business Media LLC
Date: 18-07-2022
DOI: 10.1186/S12883-022-02772-5
Abstract: The worldwide prevalence of dementia is rapidly rising. Alzheimer’s disease (AD), accounts for 70% of cases and has a 10–20-year preclinical period, when brain pathology covertly progresses before cognitive symptoms appear. The 2020 Lancet Commission estimates that 40% of dementia cases could be prevented by modifying lifestyle/medical risk factors. To optimise dementia prevention effectiveness, there is urgent need to identify in iduals with preclinical AD for targeted risk reduction. Current preclinical AD tests are too invasive, specialist or costly for population-level assessments. We have developed a new online test, TAS Test, that assesses a range of motor-cognitive functions and has capacity to be delivered at significant scale. TAS Test combines two innovations: using hand movement analysis to detect preclinical AD, and computer-human interface technologies to enable robust ‘self-testing’ data collection. The aims are to validate TAS Test to [1] identify preclinical AD, and [2] predict risk of cognitive decline and AD dementia. Aim 1 will be addressed through a cross-sectional study of 500 cognitively healthy older adults, who will complete TAS Test items comprising measures of motor control, processing speed, attention, visuospatial ability, memory and language. TAS Test measures will be compared to a blood-based AD biomarker, phosphorylated tau 181 (p-tau181). Aim 2 will be addressed through a 5-year prospective cohort study of 10,000 older adults. Participants will complete TAS Test annually and subtests of the Cambridge Neuropsychological Test Battery (CANTAB) biennially. 300 participants will undergo in-person clinical assessments. We will use machine learning of motor-cognitive performance on TAS Test to develop an algorithm that classifies preclinical AD risk (p-tau181-defined) and determine the precision to prospectively estimate 5-year risks of cognitive decline and AD. This study will establish the precision of TAS Test to identify preclinical AD and estimate risk of cognitive decline and AD. If accurate, TAS Test will provide a low-cost, accessible enrichment strategy to pre-screen in iduals for their likelihood of AD pathology prior to more expensive tests such as blood or imaging biomarkers. This would have wide applications in public health initiatives and clinical trials. ClinicalTrials.gov Identifier: NCT05194787 , 18 January 2022. Retrospectively registered.
Publisher: Elsevier BV
Date: 08-2022
Publisher: American Physiological Society
Date: 2018
Abstract: Upright stance in humans requires an intricate exchange between the neural mechanisms that control balance and those that control posture however, the distinction between these control systems is hard to discern in healthy subjects. By studying balance and postural control of a participant with c tocormia — an involuntary flexion of the trunk during standing that resolves when supine — a ergence between balance and postural control was revealed. A kinematic and kinetic investigation of standing and walking showed a stereotyped flexion of the upper body by almost 80° over a few minutes, and yet the participant’s ability to control center of mass within the base of support and to compensate for external perturbations remained intact. This unique case also revealed the involvement of automatic, tonic control of the paraspinal muscles during standing and the effects of attention. Although strength was reduced and MRI showed a reduction in muscle mass, there was sufficient strength to maintain an upright posture under voluntary control and when using geste antagoniste maneuvers or “sensory tricks” from visual, auditory, and haptic biofeedback. Dual tasks that either increased or decreased the attention given to postural alignment would decrease or increase the postural flexion, respectively. The custom-made “twister” device that measured axial resistance to slow passive rotation revealed abnormalities in axial muscle tone distribution during standing. The results suggest that the disorder in this case was due to a disruption in the automatic, tonic drive to the postural muscles and that myogenic changes were secondary. NEW & NOTEWORTHY By studying an idiopathic c tocormia case with a detailed biomechanical and sensorimotor approach, we have demonstrated unique insights into the neural control of human bipedalism 1) balance and postural control cannot be considered the same neural process, as there is a stereotyped abnormal flexed posture, without balance deficits, associated with c tocormia, and 2) posture during standing is controlled by automatic axial tone but “sensory tricks” involving sensory biofeedback to direct voluntary attention to postural alignment can override, when required.
Publisher: Springer Science and Business Media LLC
Date: 16-11-2022
DOI: 10.3758/S13415-022-01047-3
Abstract: Response-selective stopping requires cancellation of only one component of a multicomponent action. While research has investigated how delays to the continuing action components (“stopping interference”) can be attenuated by way of contextual cues of the specific stopping demands (“foreknowledge”), little is known of the underlying neural mechanisms. Twenty-seven, healthy, young adults undertook a multicomponent stop-signal task. For two thirds of trials, participants responded to an imperative (go) stimulus (IS) with simultaneous button presses using their left and right index fingers. For the remaining one third of trials, the IS was followed by a stop-signal requiring cancellation of only the left, or right, response. To manipulate foreknowledge of stopping demands, a cue preceded the IS that informed participants which hand might be required to stop (proactive) or provided no such information (reactive). Transcranial magnetic stimulation (TMS) assessed corticospinal excitability (CSE) as well as short- and long-interval interhemispheric inhibition (SIHI, LIHI) between the primary motor cortices. Proactive cues reduced, but did not eliminate, stopping interference relative to the reactive condition. Relative to TMS measures at cue onset, decreases in CSE (both hands and both cue conditions) and LIHI (both hands, proactive condition only) were observed during movement preparation. During movement cancellation, LIHI reduction in the continuing hand was greater than that in the stopping hand and greater than LIHI reductions in both hands during execution of multicomponent responses. Our results indicate that foreknowledge attenuates stopping interference and provide evidence for a novel role of LIHI, mediated via prefrontal regions, in facilitating continuing action components.
Publisher: Elsevier BV
Date: 09-2010
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 04-10-2010
Publisher: Elsevier BV
Date: 06-2022
DOI: 10.1016/J.GAITPOST.2022.04.021
Abstract: Prior work suggests there may be greater reliance on executive function for walking in older people. The pre-frontal cortex (PFC), which controls aspects of executive function, is known to be active during dual-task walking (DTW). However, there is debate on how PFC activity during DTW is impacted by ageing and the requirements of the cognitive task. Functional near infrared spectroscopy, was used to investigate how PFC activity during walking was affected by (i) healthy ageing and (ii) dual-tasks that utilise inhibition or working memory aspects of executive function. Young (n = 26, 16 females, mean 20.9 years) and older (n = 26, 16 females, mean 70.3 years) adults performed five conditions: normal walking Reciting Alternate Letters of the alphabet (RAL, requiring cognitive inhibition and working memory) during standing and walking and serial subtraction by threes (SS3, requiring working memory alone) during standing and walking. Walking speed, cognitive performance, the PFC haemodynamic response, and fear of falling ratings were analysed using linear mixed-effects modelling. Compared to quiet standing, PFC activity increased during normal walking for older adults but decreased for young adults (p < 0.01). Across both groups, fear of falling contributed to higher PFC activity levels when walking (p < 0.01). PFC activity increased during DTW, and this increase was greater when performing RAL compared to the SS3 task (p < 0.01). Although the rate of correct responses was higher for RAL, walking speed reduced more with RAL than SS3 in the young group (p = 0.01), and the rate of correct responses reduced more when walking with RAL than SS3 in the older group (p < 0.01). Older adults have increased levels of PFC activation during walking compared to younger adults and fear of falling is a cofounding factor. The interference between gait and a concurrent cognitive task is higher when the cognitive task requires inhibition.
Publisher: Elsevier BV
Date: 09-2022
DOI: 10.1016/J.JNS.2022.120336
Abstract: Across the world, Essential Tremor (ET) is the most common tremor diagnosis but up to half of these diagnoses are inaccurate. The misdiagnosis rate is particularly high in late-onset ET, when tremor begins after the age of 60 years. Currently, ET is reported to affect 5.5% of those over 65 years old and 21.7% aged over 95 but there is emerging evidence that late-onset ET has associations with dementia, mortality and more rapid progression. With ageing populations, and a range of new surgical treatments for ET, there is urgent need to clarify whether the clinical manifestations of late-onset ET are the same as for earlier-onset ET. This scoping review used MEDLINE, EMBASE and CINAHL as the information sources of published peer-reviewed research articles between 2011 and 2021. Analysis was done by narrative synthesis. 14 relevant papers were retrieved from studies conducted in Denmark, India, Italy, Germany, Spain and the US and, together, they comprised 7684 participants in total. Compared to older adults with earlier-onset ET, there is evidence that late-onset ET is associated with higher risk of cognitive impairment and dementia, higher mortality rate, faster rate of progression, lack of family history, altered cortical electrical activity, prolonged pupillary responses, and less propensity to demonstrate characteristic alcohol sensitivity. There is evidence that late-onset ET has different clinical manifestations to earlier-onset ET in particular there is higher risk of dementia and mortality. The prognosis is important for clinicians to consider when selecting candidates for deep brain stimulation surgery and also for advanced care planning.
Publisher: Wiley
Date: 10-2009
DOI: 10.1111/J.1532-5415.2009.02436.X
Abstract: To determine whether wearing multifocal glasses affects obstacle avoidance and eye and head movements during walking with and without a secondary visual task in older people. Randomized order, cross-over, controlled comparison. Falls laboratory, medical research institute. Thirty community-living adults aged 65 and older. Obstacle contacts, secondary-task errors, average head angle (HA) in pitch, and peak-to-peak pitch litude of the eye (PA-E) and the head (PA-H) were assessed during obstacle-only and dual-task trials that required participants to read a series of letters presented in front of them at eye level under multifocal and single-lens glasses conditions. When wearing multifocal lens glasses, participants performed the obstacle-only trials more slowly (P=.004) and contacted more obstacles in the dual-task trials (P=.001) than when wearing single-lens glasses. For the dual task trials under the multifocal glasses condition, greater PA-E was associated with more obstacle contacts (rho=0.409, P=.02) and greater PA-H was associated with more secondary-task errors (rho=0.583 P=.002). Lower HA was associated with more secondary-task errors (rho=0.608, P=.002) and increased PA-H (rho=0.426, P=.02). The findings demonstrate that older adults contact more obstacles while walking with their attention ided when wearing multifocal glasses. This is probably because of a failure to adopt a compensatory increase in pitch head movement, resulting in blurred vision of obstacles viewed through the lower segments of multifocal glasses.
Publisher: Wiley
Date: 24-01-2006
Publisher: Elsevier BV
Date: 2021
DOI: 10.2139/SSRN.3979578
Publisher: Oxford University Press (OUP)
Date: 07-2022
Abstract: Essential tremor (ET) is the most common cause of tremor in older adults. However, it is increasingly recognised that 30–50% of ET cases are misdiagnosed. Late-onset ET, when tremor begins after the age of 60, is particularly likely to be misdiagnosed and there is mounting evidence that it may be a distinct clinical entity, perhaps better termed ‘ageing-related tremor’. Compared with older adults with early-onset ET, late-onset ET is associated with weak grip strength, cognitive decline, dementia and mortality. This raises questions around whether late-onset ET is a pre-cognitive biomarker of dementia and whether modification of dementia risk factors may be particularly important in this group. On the other hand, it is possible that the clinical manifestations of late-onset ET simply reflect markers of healthy ageing, or frailty, superimposed on typical ET. These issues are important to clarify, especially in the era of specialist neurosurgical treatments for ET being increasingly offered to older adults, and these may not be suitable in people at high risk of cognitive decline. There is a pressing need for clinicians to understand late-onset ET, but this is challenging when there are so few publications specifically focussed on this subject and no specific features to guide prognosis. More rigorous clinical follow-up and precise phenotyping of the clinical manifestations of late-onset ET using accessible computer technologies may help us delineate whether late-onset ET is a separate clinical entity and aid prognostication.
Publisher: Wiley
Date: 29-03-2020
DOI: 10.1113/JP279171
Publisher: Elsevier BV
Date: 12-2008
DOI: 10.1016/J.NEUCLI.2008.09.001
Abstract: Good balance is an imperative skill for daily life that requires the complex integration of sensory information regarding the position of the body relative to the surroundings and the ability to generate appropriate motor responses to control body movement. Balance calls upon contributions from vision, vestibular sense, proprioception, muscle strength and reaction time. With increased age, there is a progressive loss of functioning of these systems which can contribute to balance deficits. Balance disorders represent a growing public health concern due to the association with falls and fall-related injuries, particularly in regions of the world in which high proportions of the population are elderly. Falls present one of the most serious and costly problems associated with older adulthood. Falls can mark the beginning of a decline in function and independence and are the leading cause of injury-related hospitalisation in older people. One in three people over the age of 65 years who are living in the community experience at least one fall each year and 10-15% of these falls are associated with serious injury. In economic terms, the direct and indirect costs associated with falls are large and will grow as the proportion of older people increases. Consequently, understanding age-related changes in the physiological systems imperative to balance is of utmost importance to prevent falls in older people and reduce the injury-related burden on in iduals and society.
Publisher: Wiley
Date: 15-02-2011
Publisher: Oxford University Press (OUP)
Date: 05-2007
Abstract: Deterioration with age of physiological components of balance control increases fall risk. Avoiding a fall can also require higher level cognitive processing to select correct motor and stepping responses. Here we investigate how a competing cognitive task and an obstacle to stepping affect the initiation and execution phases of choice stepping reaction times in young and older people. Three groups were studied: young persons (YOUNG: 23-40 years, n = 20), older persons with a low risk of falls (OLR: 75-86 years, n = 18), and older persons with a high risk of falls (OHR: 78-88 years, n = 22). Four conditions were examined: choice stepping, choice stepping + obstacle, choice stepping + working memory task, and choice stepping + working memory task + obstacle. Step response and transfer times were measured for each condition, in addition to hesitant stepping, contacts with the obstacle and errors made in the memory test. Older participant groups had significantly longer response and transfer times than the young group had, and the OHR group had significantly longer response and transfer times than the OLR group had. There was a significant Group x Secondary task interaction for response time (F(2,215) = 12.6, p <.001). With the memory task, response time was minimally affected in the YOUNG (7% increase, p =.11) but was slowed significantly in the OLR fallers (42% increase, p <.001) and more so in the OHR fallers (48% increase, p <.001). The obstacle had a small but significant effect on response time (9.4%) and a larger effect on transfer time (43.3%), with no differences among the groups. Errors in stepping, performing the secondary task and contacting the obstacle increased with age and fall risk. Compared with young people, older people, and more so those at risk of falling, have an impaired ability to initiate and execute quick, accurate voluntary steps, particularly in situations where attention is ided.
Publisher: Elsevier BV
Date: 2021
Publisher: Oxford University Press (OUP)
Date: 05-2007
Abstract: Deterioration with age of physiological components of balance control increases fall risk. Avoiding a fall can also require higher level cognitive processing to select correct motor and stepping responses. Here we investigate how a competing cognitive task and an obstacle to stepping affect the initiation and execution phases of choice stepping reaction times in young and older people. Three groups were studied: young persons (YOUNG: 23-40 years, n = 20), older persons with a low risk of falls (OLR: 75-86 years, n = 18), and older persons with a high risk of falls (OHR: 78-88 years, n = 22). Four conditions were examined: choice stepping, choice stepping + obstacle, choice stepping + working memory task, and choice stepping + working memory task + obstacle. Step response and transfer times were measured for each condition, in addition to hesitant stepping, contacts with the obstacle and errors made in the memory test. Older participant groups had significantly longer response and transfer times than the young group had, and the OHR group had significantly longer response and transfer times than the OLR group had. There was a significant Group x Secondary task interaction for response time (F(2,215) = 12.6, p <.001). With the memory task, response time was minimally affected in the YOUNG (7% increase, p =.11) but was slowed significantly in the OLR fallers (42% increase, p <.001) and more so in the OHR fallers (48% increase, p <.001). The obstacle had a small but significant effect on response time (9.4%) and a larger effect on transfer time (43.3%), with no differences among the groups. Errors in stepping, performing the secondary task and contacting the obstacle increased with age and fall risk. Compared with young people, older people, and more so those at risk of falling, have an impaired ability to initiate and execute quick, accurate voluntary steps, particularly in situations where attention is ided.
Publisher: Elsevier BV
Date: 07-2014
Publisher: Springer Science and Business Media LLC
Date: 18-11-2013
Publisher: Frontiers Media SA
Date: 2013
Publisher: S. Karger AG
Date: 21-07-2008
DOI: 10.1159/000146786
Abstract: i Background: /i Older people often experience unusual sleeping patterns and a poor quality of night-time sleep. Insufficient sleep has potential effects on cognition and physical functioning and therefore may increase the incidence of falls in older people. i Objectives: /i To determine the extent to which a range of physiological, psychological and health-related factors predict night-time sleep quality of older people living in self-care and assisted-care, and whether poor sleep quality is a risk factor for falls. i Methods: /i 572 people, 81 men and 491 women (mean age 79.7 years, SD 6.4), recruited from self-care retirement villages and assisted-care hostels participated in the cross-sectional study with a subgroup of 169 followed up for falls for 1 year. The main outcome measures were sleep quality and prospective falls. i Results: /i Approximately half of the s le rated their sleep quality as poor or fair. Many measures of health, medication use and mood were significantly associated with ratings of poor night-time sleep quality. Multiple regression analyses revealed poor circulation, use of psychotropic and diuretic medications, negative affect, pain, not having a friend in the village, lower fitness levels and daytime napping were significant and independent predictors of night-time sleep quality in both residential care groups. Napping daily was reported by 28% of the self-care group and 37% of the assisted-care group. Residents across both care levels who napped min during the day, or reported h sleep at night, were three times more likely to suffer multiple falls in the follow-up year when adjusting for health, medication and activity measures. i Conclusions: /i Sleep disturbances were common and associated with a variety of psychological, physiological, health and lifestyle factors. Long daytime naps and short night-time sleep periods were associated with an increased risk of falls.
Publisher: Journal of Neurosurgery Publishing Group (JNSPG)
Date: 11-2011
Abstract: While deep brain stimulation (DBS) has proven to be an effective treatment for many symptoms of Parkinson disease (PD), a deterioration of axial symptoms frequently occurs, particularly for speech and swallowing. These unfavorable effects of DBS may depend on the site of stimulation. The authors made quantitative measures of jaw velocity to compare the relative effectiveness of DBS in the globus pallidus internus (GPi) or the subthalamic nucleus (STN). This was a randomized, double-blind, and longitudinal study, with matched healthy controls. The peak velocities of self-scaled and externally scaled jaw movements were studied in 27 patients with PD before and after 6 months of bilateral DBS in the GPi or the STN. A mixed-effects model was used to identify differences in jaw velocity before DBS surgery (baseline) while off and on levodopa therapy, and after 6 months of DBS (postoperative) during 4 treatment conditions (off- and on-levodopa states with and without DBS). Self-scaled jaw velocity was impaired by the DBS procedure in the STN velocity was significantly decreased across all postoperative conditions compared with either the off- or on-levodopa baseline conditions. In contrast, the postoperative velocity in the GPi group was generally faster than the baseline off-levodopa state. Turning the DBS off and on had no effect on jaw velocity in either group. Unlike baseline, levodopa therapy postoperatively no longer increased jaw velocity in either group, and this lack of effect was not related to postoperative changes in dose. The externally scaled jaw velocity was little affected by PD, but DBS still slightly affected performance, with the STN group significantly slower than the GPi group for most conditions. The authors' results suggest that either the electrode implant in STN or the subsequent period of continuous STN stimulation negatively affected voluntary jaw velocity, including the loss of the preoperative levodopa-induced improvement. While the GPi group showed some improvement in voluntary jaw velocity postoperatively, their performance during the combination of DBS and levodopa was not different from their best medical management presurgery. The results have implications for DBS target selection, particularly for those patients with oromotor dysfunctions.
Publisher: Wiley
Date: 12-2021
DOI: 10.1002/ALZ.058732
Abstract: There is urgent need to develop population‐level digital biomarkers that can detect Alzheimer’s disease (AD) across the continuum, including the preclinical phase. This would allow risk stratification for specialist tests and early recruitment to clinical trials. Motor function declines in the preclinical phase but there has been little exploration of digital motor biomarkers. We have developed ‘TasTest’, an online test that assesses multiple cognitive domains, including movement. The aim of this study was to compare performance on TasTest with subtests of the Cambridge Neuropsychological Test Battery (CANTAB), a validated digital measure of cognitive decline, and determine how performance on the TasTest items varies with age in a large community s le of older adults. The TasTest items include measures of motor control (speed and coordination of keyboard tapping), processing speed (single and choice reaction time), attention and visual perception (identification of an animal in a distorted image), and visuospatial memory (identifying features from delayed recall of a complex figure). A total of 510 adults aged over 50 years (30% male mean 65.5 years SD 7.36), performed TasTest and CANTAB online assessments in their homes. We compared performance on TasTest items to performance on the Paired Associates Learning (PAL) task, which has been previously validated as predictive of accelerated cognitive decline (Barnett et al. 2015, Current Topics in Behavioral Neurosciences, vol 28, Springer, Cham). All TasTest items were significantly associated with PAL scores except the total number of correct responses on the reaction time tasks (Table 1). Several TasTest items had stronger correlations with age than the PAL, these included the keyboard tapping tasks, the number of correctly identified animals on the distorted image, and both simple and choice reaction times (Figure 1). Older people were able to readily complete TasTest tasks remotely from their homes, and performance on most items was significantly associated with scores on a previously validated test of cognition, and correlated with age. TasTest shows potential as a non‐invasive, scalable dementia screening tool.
No related grants have been discovered for Rebecca St George.