Talia Herman

Executive Control Deficits as a Prodrome to Falls in Healthy Older Adults: A Prospective Study Linking Thinking, Walking, and Falling

BACKGROUND Executive function (EF) deficits may increase fall risk, even among older adults with no overt cognitive impairment. Indeed, the effects of dual tasking (DT) on gait, a challenge to executive control, are more exaggerated in persons with a history of falls. Prospective evidence is, however, lacking. METHODS We prospectively evaluated whether EF predicts falls over a 2-year period among 262 community-living, healthy, and well-functioning older adults, focusing on the 201 who reported no falls during the previous year. At baseline, participants completed a computerized cognitive battery that generated an index of EF and other cognitive domains. Gait was assessed using performance-based tests and by quantifying walking during single- and dual-task conditions. RESULTS The 262 participants (mean age: 76.3 ± 4.3 years, 60.3% women) had intact cognitive function on testing, a low comorbidity index, and good mobility. The EF index predicted future falls. Among those who reported no previous falls, participants in the worst EF quartile were three times more likely to fall during the 2 years of follow-up, and they were more likely to transition from nonfaller to faller sooner. DT gait variability also predicted future falls and multiple falls, whereas other measures of cognitive function, gait, and mobility did not. CONCLUSIONS Among healthy older adults, individuals with poorer EF are more prone to falls. Higher-level cognitive functions such as those regulated by the frontal lobes are apparently needed for safe everyday navigation that demands multitasking. Optimal screening, early detection, and treatment of falls should, apparently, also target this cognitive domain.

Rhythmic auditory stimulation modulates gait variability in Parkinson's disease

Patients with Parkinsons disease (PD) walk with a shortened stride length and high stride‐to‐stride variability, a measure associated with fall risk. Rhythmic auditory stimulation (RAS) improves stride length but the effects on stride‐to‐stride variability, a marker of fall risk, are unknown. The effects of RAS on stride time variability, swing time variability and spatial‐temporal measures were examined during 100‐m walks with the RAS beat set to 100 and 110% of each subjects usual cadence in 29 patients with idiopathic PD and 26 healthy age‐matched controls. Carryover effects were also evaluated. During usual walking, variability was significantly higher (worse) in the patients with PD compared with the controls (P < 0.01). For the patients with PD, RAS at 100% improved gait speed, stride length and swing time (P < 0.02) but did not significantly affect variability. With RAS at 110%, reductions in variability were also observed (P < 0.03) and these effects persisted 2 and 15 min later. In the control subjects, the positive effects of RAS were not observed. For example, RAS increased stride time variability at 100 and 110%. These results demonstrate that RAS enables more automatic movement and reduces stride‐to‐stride variability in patients with PD. Further, these improvements are not simply a by‐product of changes in speed or stride length. After walking with RAS, there also appears to be a carryover effect that supports the possibility of motor plasticity in the networks controlling rhythmicity in PD and the potential for using RAS as an intervention to improve mobility and reduce fall risk.

Treadmill walking as an external pacemaker to improve gait rhythm and stability in Parkinson's disease

Recent reports suggest that external cueing improves stride length and gait speed in Parkinsons disease (PD). The purpose of the present study was to examine the influence of treadmill walking on gait variability. The 36 PD patients (Hoehn and Yahr stage 2–2.5) were compared to 30 controls. Subjects walked three times for 2 minutes each: (1) walking on level ground (unassisted), (2) walking on level ground while using a walker, and (3) walking on a treadmill. Stride time variability and swing time variability were significantly increased in the patients compared to the control subjects when walking on level ground with a walker. In both groups, the use of a walking aid did not significantly affect stride time variability or swing time variability, but the treadmill reduced stride time variability and swing time variability in the patients and in the controls. These results indicate that, during treadmill walking, PD subjects are able to walk with a less variable and more stable gait. Because the treadmill walking speed was set to the gait speed on level ground and because this effect was not seen with a walking aid, we suggest that the treadmill may be acting as an external cue to enhance gait rhythmicity and reduce gait variability.

Falls in outpatients with Parkinson's disease: frequency, impact and identifying factors

Falls are one of the most serious complications of gait disturbances in patients with Parkinsons disease (PD). Among previous reports, the percentage of patients with PD who fall varies between 38% to 68%. We sought to determine the frequency of falls and the factors associated with falls in a group of patients with idiopathic PD who attended an outpatient, tertiary movement disorders clinic. 350 ambulatory, non–demented patients (230 males) were studied. Mean age was 69.7 ± 10.6 years (range: 43–97 yrs) and mean duration of PD symptoms was 8.6 ± 6.2 years (range: 1–33 yrs). Assessments included characterization of demographics, disease duration, disease severity as measured by the Hoehn and Yahr Scale (H&Y), co–morbidities, the presence of depressive symptoms, the presence of urinary incontinence, use of anti–parkinsonian medications, and two performance–based tests of balance and gait (tandem standing and Timed Up & Go). Fall history was determined during three time periods: previous week, previous month, and previous year. Univariate and multivariate logistic regression models were applied to evaluate the relationship between the above–mentioned factors and falls. 46% of the subjects reported at least one fall in the previous year and 33% reported 2 or more falls and were classified as Fallers. Fallers had significantly more prolonged and advanced PD compared with Non–fallers (p = 0.001 and p < 0.001, respectively). Urinary incontinence was the factor most closely associated with falls (crude and adjusted OR were 1.95 and 5.89, respectively). Other factors significantly associated with fall status included increased Timed Up & Go times and increased PD duration. These findings confirm that falls are a common problem among patients with advanced PD and suggest easily measurable features that may be used to prospectively identify those PD patients with the greatest risk of falls.

Executive Function and Falls in Older Adults: New Findings from a Five-Year Prospective Study Link Fall Risk to Cognition

Background Recent findings suggest that executive function (EF) plays a critical role in the regulation of gait in older adults, especially under complex and challenging conditions, and that EF deficits may, therefore, contribute to fall risk. The objective of this study was to evaluate if reduced EF is a risk factor for future falls over the course of 5 years of follow-up. Secondary objectives were to assess whether single and dual task walking abilities, an alternative window into EF, were associated with fall risk. Methodology/Main Results We longitudinally followed 256 community-living older adults (age: 76.4±4.5 yrs; 61% women) who were dementia free and had good mobility upon entrance into the study. At baseline, a computerized cognitive battery generated an index of EF, attention, a closely related construct, and other cognitive domains. Gait was assessed during single and dual task conditions. Falls data were collected prospectively using monthly calendars. Negative binomial regression quantified risk ratios (RR). After adjusting for age, gender and the number of falls in the year prior to the study, only the EF index (RR: .85; CI: .74–.98, p = .021), the attention index (RR: .84; CI: .75–.94, p = .002) and dual tasking gait variability (RR: 1.11; CI: 1.01–1.23; p = .027) were associated with future fall risk. Other cognitive function measures were not related to falls. Survival analyses indicated that subjects with the lowest EF scores were more likely to fall sooner and more likely to experience multiple falls during the 66 months of follow-up (p<0.02). Conclusions/Significance These findings demonstrate that among community-living older adults, the risk of future falls was predicted by performance on EF and attention tests conducted 5 years earlier. The present results link falls among older adults to cognition, indicating that screening EF will likely enhance fall risk assessment, and that treatment of EF may reduce fall risk.

Virtual Reality for Gait Training: Can It Induce Motor Learning to Enhance Complex Walking and Reduce Fall Risk in Patients With Parkinson's Disease?

BACKGROUND Gait and cognitive disturbances are common in Parkinsons disease (PD). These deficits exacerbate fall risk and difficulties with mobility, especially during complex or dual-task walking. Traditional gait training generally fails to fully address these complex gait activities. Virtual reality (VR) incorporates principles of motor learning while delivering engaging and challenging training in complex environments. We hypothesized that VR may be applied to address the multifaceted deficits associated with fall risk in PD. METHODS Twenty patients received 18 sessions (3 per week) of progressive intensive treadmill training with virtual obstacles (TT + VR). Outcome measures included gait under usual-walking and dual-task conditions and while negotiating physical obstacles. Cognitive function and functional performance were also assessed. RESULTS Patients were 67.1 ± 6.5 years and had a mean disease duration of 9.8 ± 5.6 years. Posttraining, gait speed significantly improved during usual walking, during dual task, and while negotiating overground obstacles. Dual-task gait variability decreased (ie, improved) and Trail Making Test times (parts A and B) improved. Gains in functional performance measures and retention effects, 1 month later, were also observed. CONCLUSIONS To our knowledge, this is the first time that TT + VR has been used for gait training in PD. The results indicate that TT + VR is viable in PD and may significantly improve physical performance, gait during complex challenging conditions, and even certain aspects of cognitive function. These findings have important implications for understanding motor learning in the presence of PD and for treating fall risk in PD, aging, and others who share a heightened risk of falls.

Properties of the ‘Timed Up and Go’ Test: More than Meets the Eye

Background: The ‘timed up and go’ test (TUG) is a simple, quick and widely used clinical performance-based measure of lower extremity function, mobility and fall risk. We speculated that its properties may be different from other performance-based tests and assessed whether cognitive function may contribute to the differences among these tests in a cohort of healthy older adults. Objective: To evaluate psychometric properties of the TUG in healthy older adults in comparison to the Berg balance test (BBT) and the Dynamic Gait Index (DGI). Methods: The TUG, DGI and BBT were assessed in 265 healthy older adults (76.4 ± 4.3 years; 58.3% women) who participated in a 3-year prospective study. The Mini-Mental State Examination, digit span and verbal fluency measured cognitive function. The one-sample Kolmogorov-Smirnov test evaluated deviations from a normal distribution and Pearson’s correlation coefficients quantified associations. Results: The mean scores of the BBT, DGI and TUG were: 54.0 ± 2.4, 22.8 ± 1.5, 9.5 ± 1.7 s, respectively. The BBT and the DGI were not normally distributed (p < 0.001), but the TUG was (p = 0.713). The TUG times were mildly associated (p < 0.01) with digit span and verbal fluency and were related to future falls, while the BBT and the DGI were not. Conclusions: The TUG appears to be an appropriate tool for clinical assessment of functional mobility even in healthy older adults. It does not suffer from ceiling effect limitations, is normally distributed and is apparently related to executive function. The BBT and the DGI do not share these beneficial properties. Perhaps the transferring and turning components of the TUG help to convert this relatively simple motor task into a more complex measure that also depends on cognitive resources.

Can an accelerometer enhance the utility of the Timed Up & Go Test when evaluating patients with Parkinson's disease?

INTRODUCTION The Timed Up and Go (TUG) test is a widely used measure of mobility and fall risk in older adults and in Parkinsons disease (PD). We tested the hypothesis that body-fixed accelerometers can provide insight into TUG performance in PD patients. METHODS We examined 17 patients with PD (Hoehn and Yahr score: 2.7+/-0.7; ON state) and 15 age-matched healthy controls; mean ages were 66.8+/-5.9 years, 67.6+/-9.6 years, respectively. Subjects wore a 3D-accelerometer (ADXL330, Analog Devices) on the lower back while performing the TUG test. Sit-to-Stand and Stand-to-Sit times were extracted from the anterior-posterior (AP) signal. Parameters included Sit-to-Stand, Stand-to-Sit durations, amplitude range (Range) and slopes (Jerk). Acceleration median and standard deviation (SD) were also calculated. RESULTS Stopwatch-based TUG duration tended to be higher for the PD patients compared to the control group, although not significantly (p=0.08). In contrast, the TUG duration that was extracted from the acceleration signal was significantly (p<0.02) higher in the PD group compared to the control group. Many acceleration-parameters were also significantly different (p<0.05) between groups; most were not correlated with TUG duration. CONCLUSIONS Accelerometer-derived parameters are sensitive to group differences, indicating that PD patients have poorer mobility during specific aspects of the TUG. In addition to test duration, these measures may serve as complementary and objective bio-markers of PD to augment the evaluation of disease progression and the response to therapeutic interventions.

Effect of gait speed on gait rhythmicity in Parkinson's disease: variability of stride time and swing time respond differently

BackgroundThe ability to maintain a steady gait rhythm is impaired in patients with Parkinsons disease (PD). This aspect of locomotor dyscontrol, which likely reflects impaired automaticity in PD, can be quantified by measuring the stride-to-stride variability of gait timing. Previous work has shown an increase in both the variability of the stride time and swing time in PD, but the origins of these changes are not fully understood. Patients with PD also generally walk with a reduced gait speed, a potential confounder of the observed changes in variability. The purpose of the present study was to examine the relationship between walking speed and gait variability.MethodsStride time variability and swing time variability were measured in 36 patients with PD (Hoehn and Yahr stage 2–2.5) and 30 healthy controls who walked on a treadmill at four different speeds: 1) Comfortable walking speed (CWS), 2) 80% of CWS 3) 90% of CWS, and 4) 110% of CWS. In addition, we studied the effects of walking slowly on level ground, both with and without a walker.ResultsConsistent with previous findings, increased variability of stride time and swing time was observed in the patients with PD in CWS, compared to controls. In both groups, there was a small but significant association between treadmill gait speed and stride time variability such that higher speeds were associated with lower (better) values of stride time variability (p = 0.0002). In contrast, swing time variability did not change in response to changes in gait speed. Similar results were observed with walking on level ground.ConclusionThe present results demonstrate that swing time variability is independent of gait speed, at least over the range studied, and therefore, that it may be used as a speed-independent marker of rhythmicity and gait steadiness. Since walking speed did not affect stride time variability and swing time variability in the same way, it appears that these two aspects of gait rhythmicity are not entirely controlled by the same mechanisms. The present findings also suggest that the increased gait variability in PD is disease-related, and not simply a consequence of bradykinesia.

The interplay between gait, falls and cognition: can cognitive therapy reduce fall risk?

In this article, we briefly summarize the incidence and significant consequences of falls among older adults, the insufficient effectiveness of commonly used multifactorial interventions and the evidence linking falls and cognitive function. Recent pharmacologic and nonpharmacologic studies that evaluated the effects of cognitive therapy on fall risk are reviewed. The results of this article illustrate the potential utility of multiple, diverse forms of cognitive therapy for reducing fall risk. The article also indicates that large-scale, randomized controlled trials are warranted and that additional research is needed to better understand the pathophysiologic mechanisms underlying the interplay between human mobility, fall risk and cognitive function. Nonetheless, we suggest that multimodality interventions that combine motor and cognitive therapy should, eventually, be incorporated into clinical practice to enable older adults and patients to move safer and with a reduced fall risk.