Aner Weiss

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.

Does the Evaluation of Gait Quality During Daily Life Provide Insight Into Fall Risk? A Novel Approach Using 3-Day Accelerometer Recordings

Background. Many approaches are used to evaluate fall risk. While their properties and performance vary, most reflect performance at a specific moment or are based on subjective self-report. Objective. To quantify fall risk in the home setting using an accelerometer. Methods. Seventy-one community-living older adults were studied. In the laboratory, fall risk was assessed using performance-based tests of mobility (eg, Timed Up and Go) and usual walking abilities were quantified. Subsequently, subjects wore a triaxial accelerometer on their lower back for 3 consecutive days. Acceleration-derived measures were extracted from segments that reflected ambulation. These included total activity duration, number of steps taken, and the amplitude and width at the dominant frequency in the power spectral density, that is, parameters reflecting step-to-step variability. Afterwards, self-report of falls was collected for 6 months to explore the predictive value. Results. Based on a history of 2 or more falls, subjects were classified as fallers or nonfallers. The number of steps during the 3 days was similar (P = .42) in the fallers (7842.1 ± 6135.6) and nonfallers (9055.3 ± 6444.7). Compared with the nonfallers, step-to-step consistency was lower in the fallers in the vertical axis (amplitude fallers, 0.58 ± 0.22 psd; nonfallers, 0.71 ± 0.18 psd; P = .008); in the mediolateral axis, step-to-step consistency was higher in the fallers (P = .014). The 3-day measures improved the identification of past and future falls status (P < .005), compared to performance-based tests. Conclusions. Accelerometer-derived measures based on 3-day recordings are useful for evaluating fall risk as older adults perform daily living activities in their everyday home environment.

Objective Assessment of Fall Risk in Parkinson's Disease Using a Body-Fixed Sensor Worn for 3 Days

Background Patients with Parkinsons disease (PD) suffer from a high fall risk. Previous approaches for evaluating fall risk are based on self-report or testing at a given time point and may, therefore, be insufficient to optimally capture fall risk. We tested, for the first time, whether metrics derived from 3 day continuous recordings are associated with fall risk in PD. Methods and Materials 107 patients (Hoehn & Yahr Stage: 2.6±0.7) wore a small, body-fixed sensor (3D accelerometer) on lower back for 3 days. Walking quantity (e.g., steps per 3-days) and quality (e.g., frequency-derived measures of gait variability) were determined. Subjects were classified as fallers or non-fallers based on fall history. Subjects were also followed for one year to evaluate predictors of the transition from non-faller to faller. Results The 3 day acceleration derived measures were significantly different in fallers and non-fallers and were significantly correlated with previously validated measures of fall risk. Walking quantity was similar in the two groups. In contrast, the fallers walked with higher step-to-step variability, e.g., anterior-posterior width of the dominant frequency was larger (p = 0.012) in the fallers (0.78±0.17 Hz) compared to the non-fallers (0.71±0.07 Hz). Among subjects who reported no falls in the year prior to testing, sensor-derived measures predicted the time to first fall (p = 0.0034), whereas many traditional measures did not. Cox regression analysis showed that anterior-posterior width was significantly (p = 0.0039) associated with time to fall during the follow-up period, even after adjusting for traditional measures. Conclusions/Significance These findings indicate that a body-fixed sensor worn continuously can evaluate fall risk in PD. This sensor-based approach was able to identify transition from non-faller to faller, whereas many traditional metrics were not successful. This approach may facilitate earlier detection of fall risk and may in the future, help reduce high costs associated with falls.

Toward Automated, At-Home Assessment of Mobility Among Patients With Parkinson Disease, Using a Body-Worn Accelerometer

Objective. To develop an automated and objective method to assess mobility in Parkinson disease (PD) patients in daily-life settings and to investigate whether accelerometer-derived measures discriminate between PD and healthy controls as they walk and simulate activities of daily living (ADL). Methods. Healthy older adults (17) and patients with PD (22) wore a triaxial accelerometer on their lower back during short walks (validation study) and during a walk around the medical center to simulate daily activities (ADL simulation). The variability (consistency and rhythmicity) of stepping was assessed. The patients completed the walks before and after taking their anti-Parkinsonian medications. Frequency-based acceleration measures included dominant frequency, amplitude (strength of signal frequency), width (frequency dispersion), and slope (a combination reflecting amplitude and width) of the main frequency of the power spectral density in the 0.5- to 3.0-Hz band. A subset of the Unified Parkinson-Disease Rating Scale provided a clinical measure of gait impairment (UPDRS-Gait5). A PD patient and control wore the sensors for 3 days at home. Results. The width was larger, and the amplitude and slope were smaller in the PD patients compared to the controls in the validation study and ADL simulation (P < .02). The width decreased, and the amplitude and slope increased when patients took anti-Parkinsonian medications (P < .007). Significant correlations were observed between acceleration-derived measures and UPDRS-Gait5. The data obtained at home was similar to the clinic data. Conclusions. Frequency-derived measures are valid and sensitive estimates of stride-to-stride variability that can be used to assess the quality and consistency of walking in patients with PD in real-life settings.

Association between performance on timed up and go subtasks and mild cognitive impairment: further insights into the links between cognitive and motor function

To assess whether different Timed Up and Go (TUG) subtasks are affected differently in older adults with mild cognitive impairment (MCI) and are specific to different cognitive abilities.

Using a Body-Fixed Sensor to Identify Subclinical Gait Difficulties in Older Adults with IADL Disability: Maximizing the Output of the Timed Up and Go

Objective The identification and documentation of subclinical gait impairments in older adults may facilitate the appropriate use of interventions for preventing or delaying mobility disability. We tested whether measures derived from a single body-fixed sensor worn during traditional Timed Up and Go (TUG) testing could identify subclinical gait impairments in community dwelling older adults without mobility disability. Methods We used data from 432 older adults without dementia (mean age 83.30±7.04 yrs, 76.62% female) participating in the Rush Memory and Aging Project. The traditional TUG was conducted while subjects wore a body-fixed sensor. We derived measures of overall TUG performance and different subtasks including transitions (sit-to-stand, stand-to-sit), walking, and turning. Multivariate analysis was used to compare persons with and without mobility disability and to compare individuals with and without Instrumental Activities of Daily Living disability (IADL-disability), all of whom did not have mobility disability. Results As expected, individuals with mobility disability performed worse on all TUG subtasks (p<0.03), compared to those who had no mobility disability. Individuals without mobility disability but with IADL disability had difficulties with turns, had lower yaw amplitude (p<0.004) during turns, were slower (p<0.001), and had less consistent gait (p<0.02). Conclusions A single body-worn sensor can be employed in the community-setting to complement conventional gait testing. It provides a wide range of quantitative gait measures that appear to help to identify subclinical gait impairments in older adults.

Dual-Task Training on a Treadmill to Improve Gait and Cognitive Function in Elderly Idiopathic Fallers

Background and Purpose: Daily activities require the ability to dual task (DT), utilizing cognitive resources while walking to negotiate complex environmental conditions. For older adults, these additional cognitive demands often lead to reduced gait quality that increases the risk of falls. The aim of this study was to assess whether a combined intervention, consisting of treadmill training (TT) while performing DT, improves cognitive and motor performance in older adults with a history of multiple falls. Methods: A repeated measures design was used to evaluate the effects of training in 10 elderly fallers (mean age, 78.1 ± 5.81 y, 7 women). The progressive intensive training sessions included walking on a treadmill while practicing a variety of dual tasks 3 times a week for more than 6 weeks. Cognitive and motor measures were used to assess the effects of the intervention immediately after training and 1 month posttraining. Results: Improvements were observed in Berg Balance Scale (P = 0.02), Dynamic Gait Index (P = 0.03), gait speed during usual walking and while DT (P < 0.05), and cognitive performance as measured by the Trails Making Test B (P = 0.02). Furthermore, quality of life improved (SF-36: P = 0.01) as did physical activity (Physical Activity Scale for Elderly: P = 0.02). At 1 month postintervention, changes were not significant. Discussion and Conclusions: After 6 weeks of TT + DT program, elderly fallers demonstrated improved scores on tests of mobility, functional performance tasks, and cognition. Dual task training can be readily implemented by therapists as a component of a fall-risk reduction training program. Video Abstract available. See Video (Supplemental Digital Content 1, http://links.lww.com/JNPT/A81) for more insights from the authors.

Heart rate changes during freezing of gait in patients with Parkinson's disease†‡

Freezing of gait (FOG) is one of the most disabling symptoms that affect patients with Parkinsons disease (PD). Although the pathophysiology underlying FOG largely remains an enigma, several lines of evidence suggest that the autonomic nervous system might be involved. To this end, we tested the hypothesis that heart rate (HR) increases during FOG and, further, that HR increases just before FOG. To evaluate these hypotheses, 15 healthy older adults, 10 patients with PD who experienced FOG, and 10 patients who did not were studied. Patients with PD were tested during their “off” medication state. HR and HR variability were measured as subjects carried out tasks that frequently provoke FOG; 120 FOG episodes were evaluated. During FOG, HR increased (P = 0.001) by an average of 1.8 bpm, compared with HR measured before the beginning of FOG. HR also increased just before FOG, by 1 bpm (P < 0.0001). In contrast, during sudden stops and 180° turns, HR decreased by almost 2 bpm (P < 0.0001). HR variability was not associated with FOG. To our knowledge, these findings are the first to document the association of FOG to autonomic system activation, as manifested by HR dynamics. One explanation is that the changes in HR before and during FOG may be a sympathetic response that, secondary to limbic activation, contributes to the development of freezing. Although further studies are needed to evaluate these associations, the current results provide experimental evidence linking impaired motor blockades to autonomic nervous system function among patients with PD.

The complexity of daily life walking in older adult community-dwelling fallers and non-fallers

Complexity of human physiology and physical behavior has been suggested to decrease with aging and disease and make older adults more susceptible to falls. The present study investigates complexity in daily life walking in community-dwelling older adult fallers and non-fallers measured by a 3D inertial accelerometer sensor fixed to the lower back. Complexity was expressed using new metrics of entropy: refined composite multiscale entropy (RCME) and refined multiscale permutation entropy (RMPE). The study re-analyses data of 3 days daily-life activity originally described by Weiss et al. (2013). The data set contains inertial sensor data from 39 older persons reporting less than 2 falls and 32 older persons reporting two or more falls during the previous year. The RCME and the RMPE were derived for trunk acceleration and velocity signals from walking epochs of 50s using mean and variance coarse graining of the signals. Discriminant abilities of the entropy metrics were assessed using a partial least square discriminant analysis. Both RCME and RMPE successfully distinguished between the daily-life walking of the fallers and non-fallers (AUC>0.8) and performed better than the 35 conventional gait features investigated by Weiss et al. (2013). Higher complexity was found in the vertical and mediolateral directions in the non-fallers for both entropy metrics. These findings suggest that RCME and RMPE can be used to improve the assessment of fall risk in older people.

Associations between quantitative mobility measures derived from components of conventional mobility testing and Parkinsonian gait in older adults.

Objective To provide objective measures which characterize mobility in older adults assessed in the community setting and to examine the extent to which these measures are associated with parkinsonian gait. Methods During conventional mobility testing in the community-setting, 351 ambulatory non-demented Memory and Aging Project participants wore a belt with a whole body sensor that recorded both acceleration and angular velocity in 3 directions. We used measures derived from these recordings to quantify 5 subtasks including a) walking, b) transition from sit to stand, c) transition from stand to sit, d) turning and e) standing posture. Parkinsonian gait and other mild parkinsonian signs were assessed with a modified version of the original Unified Parkinson’s Disease Rating Scale (mUPDRS). Results In a series of separate regression models which adjusted for age and sex, all 5 mobility subtask measures were associated with parkinsonian gait and accounted for 2% to 32% of its variance. When all 5 subtask measures were considered in a single model, backward elimination showed that measures of walking sit to stand and turning showed independent associations with parkinsonian gait and together accounted for more than 35% of its variance. Cross-validation using data from a 2nd group of 258 older adults showed similar results. In similar analyses, only walking was associated with bradykinesia and sway with tremor. Interpretation Quantitative mobility subtask measures vary in their associations with parkinsonian gait scores and other parkinsonian signs in older adults. Quantifying the different facets of mobility has the potential to facilitate the clinical characterization and understanding the biologic basis for impaired mobility in older adults.