Control In Healthy Older Adults Research Articles

Transcranial Direct Current Stimulation for Improving Balance in Healthy Older Adults and Older Adults with Stroke: A Scoping Review.

Background/Objectives: Age-related decline in balance and postural control is common in healthy elders and is escalated in aging adults with stroke. Transcranial direct current stimulation (tDCS) has emerged as one of the promising brain stimulations adjoining therapeutic exercise to enhance the recovery of balance and motor functions in persons with and without neurological disorders. This review aims to summarize and compare the available evidence of the tDCS on improving balance in the older adults without neurological disorders and the older adults with stroke. Methods: The Ovid (Medline) database was searched from its inception through to 06/15/2024 for randomized controlled trials investigating tDCS for improving balance in older adults with and without stroke. Results: Overall, 20 appropriate studies (including 271 stroke subjects and 259 healthy older adults) were found. The data indicate mixed results of tDCS for improving balance in older adults with and without stroke. Conclusions: Based on current research evidence, we have not found a specific tDCS protocol that is more effective than other tDCS protocols for improving balance and postural control in healthy older adults and older adults with stroke. Further research should explore the ideal tDCS approach, possibly in conjunction with standard interventions, to optimize postural control and balance in healthy older adults and older adults with stroke.

Mediolateral foot placement control can be trained: Older adults learn to walk more stable, when ankle moments are constrained.

Falls are a problem, especially for older adults. Placing our feet accurately relative to the center-of-mass helps us to prevent falling during gait. The degree of foot placement control with respect to the center-of mass kinematic state is decreased in older as compared to young adults. Here, we attempted to train mediolateral foot placement control in healthy older adults. Ten older adults trained by walking on shoes with a narrow ridge underneath (LesSchuh), restricting mediolateral center-of-pressure shifts. As a training effect, we expected improved foot placement control during normal walking. A training session consisted of a normal walking condition, followed by a training condition on LesSchuh and finally an after-effect condition. Participants performed six of such training sessions, spread across three weeks. As a control, before the first training session, we included two similar sessions, but on normal shoes only. We evaluated whether a training effect was observed across sessions and weeks in a repeated-measures design. Whilst walking with LesSchuh, the magnitude of foot placement error reduced half-a-millimeter between sessions within a week (cohen's d = 0.394). As a training effect in normal walking, the magnitude of foot placement errors was significantly lower compared to the control week, by one millimeter in weeks 2 (cohen's d = 0.686) and 3 (cohen's d = 0.780) and by two millimeters in week 4 (cohen's d = 0.875). Local dynamic stability of normal walking also improved significantly. More precise foot placement may thus have led to improved stability. It remains to be determined whether the training effects were the result of walking on LesSchuh or from repeated treadmill walking itself. Moreover, enhancement of mechanisms beyond the scope of our outcome measures may have improved stability. At the retention test, gait stability returned to similar levels as in the control week. Yet, a reduction in foot placement error persisted.

Healthy aging reduces dynamic balance control as measured by the simplified Star Excursion Balance Test

BackgroundDetecting and classifying factors that contribute to age-related balance decline are essential for targeted interventions. Dynamic postural tests that challenge neuromuscular balance control are important to detect subtle deficits that affect functional balance in healthy aging. Research questionHow does healthy aging affect specific components of dynamic postural control as measured by the simplified Star Excursion Balance Test (SEBT)? MethodsTwenty healthy younger (18–39 years) and twenty healthy older (58–74 years) adults performed the standardized simplified SEBT, which involved standing on one leg and reaching the contralateral leg as far as possible in the anterior, posteromedial, and posterolateral directions. Optical motion capture was used to quantify the maximum reach distance normalized by body height (%H) for three repeated trials in each direction per leg. Linear mixed effects models and pairwise comparisons of estimated marginal means were used to assess differences (p < 0.05) in normalized maximum reach distance by age group, reach direction, and leg dominance. Intersubject and intrasubject variability were also assessed by age group using coefficients of variation (CV). ResultsHealthy older adults had less dynamic postural control compared to younger adults, with shorter reach distances in the anterior (7.9 %), posteromedial (15.8 %), and posterolateral (30.0 %) directions (p < 0.05). Leg dominance and sex did not significantly affect SEBT score for either age group (p > 0.05). Low intrasubject variability (CV<0.25 %) was found for repeated trials in both the older and younger participants. Therefore, the comparatively higher intersubject variability (Range CV=8–25 %) was mostly attributed to differences in SEBT performance across participants. SignificanceQuantifying dynamic postural control in healthy older adults in a clinical setting is important for early detection of balance decline and guiding targeted and effective treatment. These results support that the simplified SEBT is more challenging for healthy older adults, who may benefit from dynamic postural training to mitigate age-related decline.

Influence of tDCS over right inferior frontal gyrus and pre-supplementary motor area on perceptual decision-making and response inhibition: A healthy ageing perspective

A wide body of literature suggests that transcranial direct current stimulation (tDCS) administered over the prefrontal cortex can improve executive function – including decision-making and inhibitory control – in healthy young adults. However, the effects of tDCS in older adults are largely unknown. Here, using a double-blind, sham-controlled approach, changes in a combined perceptual decision-making and inhibitory control task were assessed before and after the application of tDCS (1 mA, 20 minute) targeting the right inferior frontal gyrus (rIFG) or pre-supplementary motor area (preSMA) in 42 young (18–34 years) and 41 older (60–80 years) healthy adults. Compared to sham stimulation, anodal tDCS over the preSMA improved decision-making speed for both age groups. Furthermore, the inhibitory control performance of older and younger adults was improved by preSMA and rIFG stimulation, respectively. This study provides evidence that tDCS can improve both perceptual decision-making and inhibitory control in healthy older adults, with the causal role of the preSMA and rIFG regions in cognitive control appearing to vary as a function of healthy ageing.

Can Transcranial Direct Current Stimulation Enhance Functionality in Older Adults? A Systematic Review.

Transcranial direct current stimulation (tDCS) is a non-invasive, easy to administer, well-tolerated, and safe technique capable of affecting brain excitability, both at the cortical and cerebellum levels. However, its effectiveness has not been sufficiently assessed in all population segments or clinical applications. This systematic review aimed at compiling and summarizing the currently available scientific evidence about the effect of tDCS on functionality in older adults over 60 years of age. A search of databases was conducted to find randomized clinical trials that applied tDCS versus sham stimulation in the above-mentioned population. No limits were established in terms of date of publication. A total of 237 trials were found, of which 24 met the inclusion criteria. Finally, nine studies were analyzed, including 260 healthy subjects with average age between 61.0 and 85.8 years. Seven of the nine included studies reported superior improvements in functionality variables following the application of tDCS compared to sham stimulation. Anodal tDCS applied over the motor cortex may be an effective technique for improving balance and posture control in healthy older adults. However, further high-quality randomized controlled trials are required to determine the most effective protocols and to clarify potential benefits for older adults.

Brain connectivity during simulated balance in older adults with and without Parkinson's disease

Individuals with Parkinson’s disease often experience postural instability, a debilitating and largely treatment-resistant symptom. A better understanding of the neural substrates contributing to postural instability could lead to more effective treatments. Constraints of current functional neuroimaging techniques, such as the horizontal orientation of most MRI scanners (forcing participants to lie supine), complicates investigating cortical and subcortical activation patterns and connectivity networks involved in healthy and parkinsonian balance control. In this cross-sectional study, we utilized a newly-validated MRI-compatible balance simulator (based on an inverted pendulum) that enabled participants to perform balance-relevant tasks while supine in the scanner. We utilized functional MRI to explore effective connectivity underlying static and dynamic balance control in healthy older adults (n = 17) and individuals with Parkinson’s disease while on medication (n = 17). Participants performed four tasks within the scanner with eyes closed: resting, proprioceptive tracking of passive ankle movement, static balancing of the simulator, and dynamic responses to random perturbations of the simulator. All analyses were done in the participant's native space without spatial transformation to a common template. Effective connectivity between 57 regions of interest was computed using a Bayesian Network learning approach with false discovery rate set to 5%. The first 12 principal components of the connection weights, binomial logistic regression, and cross-validation were used to create 4 separate models: contrasting static balancing vs {rest, proprioception} and dynamic balancing vs {rest, proprioception} for both controls and individuals with Parkinson’s disease. In order to directly compare relevant connections between controls and individuals with Parkinson’s disease, we used connections relevant for predicting a task in either controls or individuals with Parkinson’s disease in logistic regression with Least Absolute Shrinkage and Selection Operator regularization. During dynamic balancing, we observed decreased connectivity between different motor areas and increased connectivity from the brainstem to several cortical and subcortical areas in controls, while individuals with Parkinson’s disease showed increased connectivity associated with motor and parietal areas, and decreased connectivity from brainstem to other subcortical areas. No significant models were found for static balancing in either group. Our results support the notion that dynamic balance control in individuals with Parkinson’s disease relies more on cortical motor areas compared to healthy older adults, who show a preference of subcortical control during dynamic balancing.

Age-Related Deficits in Binocular Vision Are Associated With Poorer Inhibitory Control in Healthy Older Adults.

A robust association between reduced visual acuity and cognitive function in older adults has been revealed in large population studies. The aim of this work was to assess the relation between stereoacuity, a key aspect of binocular vision, and inhibitory control, an important component of executive functions. Inhibition was tested using the antisaccade task in older adults with normal or reduced stereopsis (study 1), and in young adults with transiently reduced stereopsis (study 2). Older adults with reduced stereopsis made significantly more errors on the antisaccade task in comparison to those with normal stereopsis. Specifically, there was a significant correlation between stereoacuity and antisaccade errors (r = 0.27, p = 0.019). In contrast, there were no significant differences in antisaccade errors between the normal and reduced stereopsis conditions in the young group. Altogether, results suggest that the association between poorer stereopsis and lower inhibitory control in older adults might arise due to central nervous system impairment that affects the processing of binocular disparity and antisaccades. These results add to a growing body of literature, which highlights the interdependence of sensory and cognitive decline in older adults.

Catecholaminergic modulation of the cost of cognitive control in healthy older adults.

Catecholamines have long been associated with cognitive control and value-based decision-making. More recently, we have shown that catecholamines also modulate value-based decision-making about whether or not to engage in cognitive control. Yet it is unclear whether catecholamines influence these decisions by altering the subjective value of control. Thus, we tested whether tyrosine, a catecholamine precursor altered the subjective value of performing a demanding working memory task among healthy older adults (60-75 years). Contrary to our prediction, tyrosine administration did not significantly increase the subjective value of conducting an N-back task for reward, as a main effect. Instead, in line with our previous study, exploratory analyses indicated that drug effects varied as a function of participants' trait impulsivity scores. Specifically, tyrosine increased the subjective value of conducting an N-back task in low impulsive participants, while reducing its value in more impulsive participants. One implication of these findings is that the over-the-counter tyrosine supplements may be accompanied by an undermining effect on the motivation to perform demanding cognitive tasks, at least in certain older adults. Taken together, these findings indicate that catecholamines can alter cognitive control by modulating motivation (rather than just the ability) to exert cognitive control.

Water Immersion Affects Episodic Memory and Postural Control in Healthy Older Adults.

Previous research has reported that younger adults make fewer cognitive errors on an auditory vigilance task while in chest-deep water compared with on land. The purpose of this study was to extend this previous work to include older adults and to examine the effect of environment (water vs land) on linear and nonlinear measures of postural control under single- and dual-task conditions. Twenty-one older adult participants (age = 71.6 ± 8.34 years) performed a cognitive (auditory vigilance) and motor (standing balance) task separately and simultaneously on land and in chest-deep water. Listening errors (n = count) from the auditory vigilance test and sample entropy (SampEn), center of pressure area, and velocity for the balance test served as dependent measures. Environment (land vs water) and task (single vs dual) comparisons were made with a Wilcoxon matched-pair test. Listening errors were 111% greater during land than during water environments (single-task = 4.0 ± 3.5 vs 1.9 ± 1.7; P = .03). Conversely, SampEn values were 100% greater during water than during land environments (single-task = 0.04 ± 0.01 vs 0.02 ± 0.01; P < .001). Center of pressure area and velocity followed a similar trend to SampEn with respect to environment differences, and none of the measures were different between single- and dual-task conditions (P > .05). The findings of this study expand current support for the potential use of partial aquatic immersion as a viable method for challenging both cognitive and motor abilities in older adults.

Investigating links between habitual physical activity, cerebrovascular function, and cognitive control in healthy older adults

A growing body of evidence indicates regular physical activity benefits older adults’ cognitive functioning, particularly when a high level of cognitive control is required. Recent research has pointed to improved cerebrovascular function as one mechanism through which such benefits might arise. This study built on previous research by investigating in 51 healthy older adults aged 60–72 years relationships between habitual physical activity, cerebrovascular function (indicated by resting cerebral blood flow velocity in the middle cerebral artery [n = 42], and its responsiveness to hypercapnia [n = 26] and hypocapnia [n = 25]), and cognitive control (inhibition and switching). Linear regression analyses showed moderate positive associations between physical activity and inhibitory control, but not cerebrovascular function. There were also no significant relationships between the cerebrovascular measures and cognitive control. These results indicate that regular engagement in physical activity is associated with superior inhibitory control in older adulthood, but cerebrovascular function was not found to explain those relationships. Taken together, the current findings reinforce reports of positive links between habitual physical activity and cognition in healthy older adults, but also signal that interrelationships with cerebrovascular function may be more complex than currently indicated by the literature, necessitating further research to elucidate the role cerebrovascular function might play in accounting for physical activity-cognition links in healthy older adults.

HoppingExercise Training Improves Postural Control in Healthy Older Adults

HoppingExercise Training Improves Postural Control in Healthy Older Adults

Two Weeks of Reduced Steps Disrupts Integrated Rates of Muscle Protein Synthesis and Glycemic Control in Healthy Older Adults

Transient periods of physical inactivity can result in losses of skeletal muscle mass and reductions in insulin sensitivity. These metabolic impairments may not be fully recovered, particularly in older individuals.1 We aimed to examine the impact of two weeks of reduced steps followed by two weeks of recovery, on lean body mass (LBM), integrated rates of myofibrillar protein synthesis (MPS), single fiber cross‐sectional area (fCSA), and indices of glycemic control (HOMA‐IR and MATSUDA) in response to an oral glucose tolerance test. We also examined changes in oxidative phosphorylation protein complex content, phosphorylation of other related signaling molecules, and concentration of circulating inflammatory markers. Twenty‐two healthy older adults (12 men, 10 women, 69±4yr [all data mean±SD]) underwent 7d of monitored normal activity at baseline (BL) before reducing their daily step‐count from 7362±3294 to 990±97 steps.d−1 for 14d (SR). Habitual step count was then recovered for a period of 14d (RC). Integrated rates of muscle protein synthesis (MPS) were reduced from BL at SR (BL 1.51±0.07 to SR 1.33±0.05 %.d−1, p&lt;0.05) and were not restored at RC (1.34±0.14 %.d−1). Women displayed significantly greater rates of integrated MPS at BL compared to men (1.56±0.06 vs. 1.47±0.04 %.d−1, p&lt;0.05). HOMA‐IR increased from BL to SR (2.6±0.4 to 3.8±0.9, p&lt;0.05) and MATSUDA decreased (3.9±0.7 to 2.9±0.4, p&lt;0.05), neither recovered at RC. Glucose AUC was significantly elevated from BL at SR (368±137 to 442±142, p&lt;0.05) and was not fully recovered from SR at RC (393±15). Insulin AUC increased from BL to SR (3372±889 to 3972±1008, p&lt;0.05) and was still elevated at RC (3865±716). Circulating plasma TNF‐a was significantly increased from BL at SR (11.78±2.84 to 15.41±4.64 pg.mL−1, p&lt;0.05) and was still elevated above BL at RC (14.28±3.76 pg.mL−1). Plasma IL‐6 concentration was also significantly increased from BL at SR (8.33±3.06 to 10.84± 4.35 pg.mL−1, p&lt;0.05) and remained elevated at RC (9.99±4.37 pg.mL−1). There was no detectable impact of step reduction on LBM, fCSA, fiber type distribution, or the content of oxidative phosphorylation protein complexes at any time point. Additionally, step reduction failed to impact the phosphorylation status of ACCSer212, AktSer473, mTORSer2448, Ulk1Ser757, and Ulk1Ser55 at BL, SR, and RC. These data demonstrate that two weeks of step reduction leads to lowered rates of MPS that are accompanied by appearance of a diabetic phenotype, and markers of an inflammatory state, which are not recovered on return to a normal daily step count in healthy older adults. Ultimately, proactive interventions such as exercise or pharmaceuticals may be required to reverse decrements in metabolic health with transient periods of physical inactivity in this population.Support or Funding InformationSupported by the Canadian Diabetes Association

Commentary: Older adults can improve compensatory stepping with repeated postural perturbations.

A commentary on: Older adults can improve compensatory stepping with repeated postural perturbations by Dijkstra,B.W., Horak,F.B., Kamsma,Y.P.T., and Peterson,D.S.(2015).Front.AgingNeurosci. 7:201. doi:10.3389/fnagi.2015.00201. In sum, the results of Dijkstra etal. (2015) are of importance and significance for the field of falls prevention and stability control in aging. In particular, the work highlights the importance of multidirectional step or perturbation training, due to a lack of transfer across tasks. Whether this would hold for multidirectional gait perturbations is unclear, due to the influence of forward velocity during walking. Future work should explore different types, intensities and frequencies of perturbations in order to determine the most effective strategy for improving dynamic stability control in healthy older adults and inpatients with declined locomotor performance and increased falls risk. Finally, as Dijkstra etal. (2015) and previous studies found floor effects in the adaptation of young participants, further attempts should be made to appropriately scale perturbations to participant or groupability, in order to reliably compare adaptation across different groups.

Abstract 18258: High-intensity Interval Training Improves Aerobic Capacity and Metabolic Risk Factors in Older Adults: A Randomized Controlled Trial

Introduction: Aging is associated with increased cardiovascular disease risk including reduced aerobic capacity and increased metabolic risk factors. Aerobic exercise training improves the risk for cardiovascular disease. The optimal exercise regimen for older adults, however, remains unknown. We tested the hypothesis that high-intensity interval training (HIIT) would be more effective than isocaloric moderate-intensity continuous training (MICT) in improving aerobic capacity and metabolic risks factors in older adults. Methods: Thirty eight sedentary older adults (age 65±1.0 yrs; mean±SE), free of cardiovascular disease, were randomly assigned to HIIT (n=13), MICT (n=13) or non-exercise control group (n=12). HIIT consisted of cycling at alternating intensities of 90 and 70% maximal heart rate for 40 minutes while MICT consisted of cycling at 70% maximal heart rate for 47 minutes. HIIT and MICT were performed on Airdyne bicycles, 4 days/week for 8 weeks, under supervision. Aerobic capacity was assessed by peak oxygen consumption during an incremental treadmill test. Metabolic risk factors included fasting lipid profile, glucose, insulin, and insulin resistance (homeostasis model assessment; HOMA-IR). Body composition was assessed using dual-energy x-ray absorptiometry. All measures were obtained at baseline and following the intervention. Results: Peak oxygen consumption increased by 2.8 ml/kg/min (23.0±1.6 vs. 25.7±1.5, pre- vs. post-intervention; P &lt;0.05) in HIIT, but did not change in MICT and control group (26.0±1.5 vs. 26.2±1.4 and 23.5±1.4 vs. 24.0±1.4, respectively; P &gt;0.05). Insulin and HOMA-IR improved only in HIIT (-1.9±0.6μU/ml and -0.42±0.16, P &lt;0.05; respectively) and these changes were negatively associated with the change in peak oxygen consumption (r=-0.37, P &lt;0.05 for both). Overall, lipids, body weight, body fat, and fat-free mass did not change in response to the intervention in any of the groups (P&gt;0.05). Conclusions: HIIT but not MICT improves aerobic capacity and glucose control in healthy older adults without affecting lipids or body composition.

Differential contributions of dorso-ventral and rostro-caudal prefrontal white matter tracts to cognitive control in healthy older adults.

Prefrontal cortex mediates cognitive control by means of circuitry organized along dorso-ventral and rostro-caudal axes. Along the dorso-ventral axis, ventrolateral PFC controls semantic information, whereas dorsolateral PFC encodes task rules. Along the rostro-caudal axis, anterior prefrontal cortex encodes complex rules and relationships between stimuli, whereas posterior prefrontal cortex encodes simple relationships between stimuli and behavior. Evidence of these gradients of prefrontal cortex organization has been well documented in fMRI studies, but their functional correlates have not been examined with regard to integrity of underlying white matter tracts. We hypothesized that (a) the integrity of specific white matter tracts is related to cognitive functioning in a manner consistent with the dorso-ventral and rostro-caudal organization of the prefrontal cortex, and (b) this would be particularly evident in healthy older adults. We assessed three cognitive processes that recruit the prefrontal cortex and can distinguish white matter tracts along the dorso-ventral and rostro-caudal dimensions –episodic memory, working memory, and reasoning. Correlations between cognition and fractional anisotropy as well as fiber tractography revealed: (a) Episodic memory was related to ventral prefrontal cortex-thalamo-hippocampal fiber integrity; (b) Working memory was related to integrity of corpus callosum body fibers subserving dorsolateral prefrontal cortex; and (c) Reasoning was related to integrity of corpus callosum body fibers subserving rostral and caudal dorsolateral prefrontal cortex. These findings confirm the ventrolateral prefrontal cortex's role in semantic control and the dorsolateral prefrontal cortex's role in rule-based processing, in accordance with the dorso-ventral prefrontal cortex gradient. Reasoning-related rostral and caudal superior frontal white matter may facilitate different levels of task rule complexity. This study is the first to demonstrate dorso-ventral and rostro-caudal prefrontal cortex processing gradients in white matter integrity.

Intermittent use of an “anchor system” improves postural control in healthy older adults

Haptic information, provided by a non-rigid tool (i.e., an “anchor system”), can reduce body sway in individuals who perform a standing postural task. However, it was not known whether or not continuous use of the anchor system would improve postural control after its removal. Additionally, it was unclear as to whether or not frequency of use of the anchor system is related to improved control in older adults. The present study evaluated the effect of the prolonged use of the anchor system on postural control in healthy older individuals, at different frequencies of use, while they performed a postural control task (semi-tandem position). Participants were divided into three groups according to the frequency of the anchor system's use (0%, 50%, and 100%). Pre-practice phase (without anchor) was followed by a practice phase (they used the anchor system at the predefined frequency), and a post-practice phase (immediate and late-without anchor). All three groups showed a persistent effect 15min after the end of the practice phase (immediate post-practice phase). However, only the 50% group showed a persistent effect in the late post-practice phase (24h after finishing the practice phase). Older adults can improve their postural control by practicing the standing postural task, and use of the anchor system limited to half of their practice time can provide additional improvement in their postural control.

Effects of whole body vibration training on postural control in older individuals: A 1 year randomized controlled trial

This randomized controlled trial investigated the effects of a 12 month whole body vibration training program on postural control in healthy older adults. Two hundred and twenty people were randomly assigned to a whole body vibration group ( n = 94), a fitness group ( n = 60) or a control group ( n = 66). The whole body vibration and fitness groups trained three times a week for 1 year. The vibration group performed exercises on a vibration platform and the fitness group performed cardiovascular, strength, balance and stretching exercises. Balance was measured using dynamic computerized posturography at baseline and after 6 and 12 months. Whole body vibration training was associated with reduced falls frequency on a moving platform when vision was disturbed and improvements in the response to toes down rotations at the ankle induced by the moving platform. The fitness group showed reduced falls frequency on the moving surface when vision was disturbed. Thus, whole body vibration training may improve some aspects of postural control in community dwelling older individuals.