Monitoring Gait and Physical Activity of Elderly Frail Individuals in Free-Living Environment: A Feasibility Study

INTRODUCTION

Frailty is conventionally diagnosed using clinical tests and self-reported assessments. However, digital health technologies (DHTs), such as wearable accelerometers, can capture physical activity and gait during daily life, enabling more objective assessments. In this study, we assess the feasibility of deploying DHTs in community-dwelling older individuals, and investigate the relationship between digital measurements of physical activity and gait in naturalistic environments and participants' frailty status, as measured by conventional assessments.

METHODS

Fried Frailty Score (FFS) was used to classify fifty healthy individuals as non-frail (FFS = 0, n/female = 21/11, mean ± SD age: 71.10 ± 3.59 years), pre-frail (FFS = 1-2, n/female = 23/9, age: 73.74 ± 5.52 years), or frail (FFS = 3+, n/female = 6/6, age: 70.70 ± 6.53 years). Participants wore wrist-worn and lumbar-worn GENEActiv accelerometers (Activinsights Ltd., Kimbolton, UK) during three in-laboratory visits, and at-home for 2 weeks, to measure physical activity and gait. After this period, they completed a comfort and usability questionnaire. Compliant days at-home were defined as follows: those with ≥18 h of wear time, for the wrist-worn accelerometer, and those with ≥1 detected walking bout, for the lumbar-worn accelerometer. For each at-home measurement, a group analysis was performed using a linear regression model followed by ANOVA, to investigate the effect of frailty on physical activity and gait. Correlation between at-home digital measurements and conventional in-laboratory assessments was also investigated.

RESULTS

Participants were highly compliant in wearing the accelerometers, as 94% indicated willingness to wear the wrist device, and 66% the lumbar device, for at least 1 week. Time spent in sedentary activity and time spent in moderate activity as measured from the wrist device, as well as average gait speed and its 95th percentile from the lumbar device were significantly different between frailty groups. Moderate correlations between digital measurements and self-reported physical activity were found.

CONCLUSIONS

This work highlights the feasibility of deploying DHTs in studies involving older individuals. The potential of digital measurements in distinguishing frailty phenotypes, while unobtrusively collecting unbiased data, thus minimizing participants' travels to sites, will be further assessed in a follow-up study.

Multimodal Wearable Sensors to Measure Gait and Voice

Background

Traditional measurement systems utilized in clinical trials are limited because they are episodic and thus cannot capture the day-to-day fluctuations and longitudinal changes that frequently affect patients across different therapeutic areas.

Objectives

The aim of this study was to collect and evaluate data from multiple devices, including wearable sensors, and compare them to standard lab-based instruments across multiple domains of daily tasks.

Methods

Healthy volunteers aged 18-65 years were recruited for a 1-h study to collect and assess data from wearable sensors. They performed walking tasks on a gait mat while instrumented with a watch, phone, and sensor insoles as well as several speech tasks on multiple recording devices.

Results

Step count and temporal gait metrics derived from a single lumbar accelerometer are highly precise; spatial gait metrics are consistently 20% shorter than gait mat measurements. The insole's algorithm only captures about 72% of steps but does have precision in measuring temporal gait metrics. Mobile device voice recordings provide similar results to traditional recorders for average signal pitch and sufficient signal-to-noise ratio for analysis when hand-held. Lossless compression techniques are advised for signal processing.

Conclusions

Gait metrics from a single lumbar accelerometer sensor are in reasonable concordance with standard measurements, with some variation between devices and across individual metrics. Finally, participants in this study were familiar with mobile devices and had high acceptance of potential future continuous wear for clinical trials.

Passive immunotherapy targeting amyloid-β reduces cerebral amyloid angiopathy and improves vascular reactivity

Prominent cerebral amyloid angiopathy is often observed in the brains of elderly individuals and is almost universally found in patients with Alzheimer’s disease. Cerebral amyloid angiopathy is characterized by accumulation of the shorter amyloid-β isoform(s) (predominantly amyloid-β40) in the walls of leptomeningeal and cortical arterioles and is likely a contributory factor to vascular dysfunction leading to stroke and dementia in the elderly. We used transgenic mice with prominent cerebral amyloid angiopathy to investigate the ability of ponezumab, an anti-amyloid-β40 selective antibody, to attenuate amyloid-β accrual in cerebral vessels and to acutely restore vascular reactivity. Chronic administration of ponezumab to transgenic mice led to a significant reduction in amyloid and amyloid-β accumulation both in leptomeningeal and brain vessels when measured by intravital multiphoton imaging and immunohistochemistry. By enriching for cerebral vascular elements, we also measured a significant reduction in the levels of soluble amyloid-β biochemically. We hypothesized that the reduction in vascular amyloid-β40 after ponezumab administration may reflect the ability of ponezumab to mobilize an interstitial fluid pool of amyloid-β40 in brain. Acutely, ponezumab triggered a significant and transient increase in interstitial fluid amyloid-β40 levels in old plaque-bearing transgenic mice but not in young animals. We also measured a beneficial effect on vascular reactivity following acute administration of ponezumab, even in vessels where there was a severe cerebral amyloid angiopathy burden. Taken together, the beneficial effects ponezumab administration has on reducing the rate of cerebral amyloid angiopathy deposition and restoring cerebral vascular health favours a mechanism that involves rapid removal and/or neutralization of amyloid-β species that may otherwise be detrimental to normal vessel function.

Hydrogen peroxide modulates the Kv1.5 channel expressed in a mammalian cell line

Reactive oxygen species have been implicated in different types of cardiac arrhythmias including human atrial fibrillation. Kv1.5, the presumed molecular correlate of I(Kur), is an important determinant of human atrial repolarization. The aim of this study was to assess the effects of H(2)O(2), at pathophysiologically relevant concentrations (20-1,000 microM), on Kv1.5 expressed in Chinese hamster ovary cell line. Kv1.5 cDNA in pcDNA3 expression vector and CD8, a surface marker protein, were cotransfected in cells by calcium phosphate precipitation. Kv1.5 activation kinetics were significantly accelerated while the activation curve was negatively shifted by 10 mV (V(1/2) changed from -9.3 to -19.0 mV) in the presence of 100 microM H(2)O(2). The shift in Kv1.5 peak current I-V curve was voltage-dependent, the current amplitude being increased for voltages <+20 mV but decreased for high depolarizing voltages. The rapid activation time constant obtained from a bi-exponential fitting was decreased from 16.1+/-3.4 ms to 8.8+/-1.5 ms for a -20 mV depolarization ( n=9; P=0.01) and from 4.3+/-2.1 ms to 2.3+/-0.4 ms when cells were depolarized to +20 mV ( P<0.05). Kv1.5 steady-state inactivation was not modified by H(2)O(2). Intracellular application of SOD or catalase reduced the H(2)O(2) induced shift of activation I-V curve and SOD significantly decreased Kv1.5 amplitude at +40 mV ( n=9; P<0.05). In conclusion, H(2)O(2) increased Kv1.5 current amplitude at voltages corresponding to the action potential repolarization phase and accelerated Kv1.5 channel opening. These changes can reduce the action potential duration, leading to a shortening of the atrial effective refractory period. H(2)O(2)-induced changes in Kv1.5 properties could thus be involved in initiation or perpetuation of AF.

Hydrogen peroxide modifies the kinetics of HERG channel expressed in a mammalian cell line

Reactive oxygen species such as H2O2 were shown to influence both electrical and contractile properties of the heart. H2O2 modulates action potential duration and leads to reperfusion-induced arrhythmias. As these effects could involve the modulation of repolarizing currents, we assessed effects of H2O2 on HERG (which encodes the cardiac potassium channel I(Kr)) expressed in Chinese hamster ovary cells. HERG currents were recorded using the whole-cell patch-clamp technique. HERG activation and deactivation were accelerated when cells were superfused with 30 microM, 100 microM, or 1 mM H2O2. For example, at 1 mM H2O2, tau(act) was decreased from 862 +/- 178 to 633 +/- 151 ms (P < 0.05; n = 6), and fast tau(deact) was reduced from 286 +/- 47 to 151 +/- 18 ms (P < 0.05; n = 6). A negative shift of V1/2 was also observed (from -1.9 to -13.7 mV with 30 microM H2O2; P < 0.05), reflecting the acceleration of the activating current. Effects of H2O2 superfusion were prevented by intracellular application of catalase but superoxide dismutase prevented only H2O2-induced acceleration of activation. This indicates that H2O2 diffuses intracellularly before acting on HERG and that its effects on activation but not deactivation are mediated by the superoxide anion. Moreover, tau(act) decrease preceded fast tau(deact) decrease by about 4 min, suggesting that these effects were not produced by the same intracellular pathway or at the same site on HERG protein. Acceleration of HERG activation kinetics leads to an increase of outward current during the plateau phase of the action potential. This could suggest a reason for H2O2-induced shortening of the action potential. The faster HERG deactivation could be involved in reperfusion-induced arrhythmias by reducing K+ conductance in the early diastole, thus increasing the risks of premature beats.