Estimating sleep from multisensory armband measurements: validity and reliability in teens

Given the recognition that sleep may influence obesity risk, there is increasing interest in measuring sleep parameters within obesity studies. The goal of the current analyses was to determine whether the SenseWear^® Pro3 Armband (armband), typically used to assess physical activity, is reliable at assessing sleep parameters. The armband was compared with the AMI Motionlogger^® (actigraph), a validated activity monitor for sleep assessment, and with polysomnography, the gold standard for assessing sleep. Participants were 20 adolescents (mean age = 15.5 years) with a mean body mass index percentile of 63.7. All participants wore the armband and actigraph on their non‐dominant arm while in‐lab during a nocturnal polysomnographic recording (600 min). Epoch‐by‐epoch sleep/wake data and concordance of sleep parameters were examined. No significant sleep parameter differences were found between the armband and polysomnography; the actigraph tended to overestimate sleep and underestimate wake compared with polysomnography. Both devices showed high sleep sensitivity, but lower wake detection rates. Bland–Altman plots showed large individual differences in armband sleep parameter concordance rates. The armband did well estimating sleep overall, with group results more similar to polysomnography than the actigraph; however, the armband was less accurate at an individual level than the actigraph.     

Nerve stimulator for regional anaesthesia procedures with automatic interactive closed-loop control

Abstract

Peripheral nerve stimulators have widespread among anaesthesiologists and remain a popular technique. However, in commercial devices, the user has to manually adjust stimulus intensity. Thus, the aim of this study is to propose a method that allows automating the current intensity control. An earlier nerve stimulator prototype was modified to add an accelerometer and an sEMG module. The choice of these two sensors is aimed at the possibility of observing the mechanical and electrical responses of the muscle contraction evoked by the stimulation. The tests were performed in two steps. The first step was to observe how the sensors behave during stimulation and muscle contraction. The second step was to implement a control algorithm and to validate the automation technique. Comparing the two methods, no significant differences were found on procedure time (manual: 12.5?±?2.3; automatic: 11.6?±?1.9; ρ?=0.380) and blockade latency time (manual: 11.6?±?1.1; automatic: 11.9?±?1.2; ρ?=0.524). Comparing needle-nerve distance in manual or automatic mode, no significant differences were found for 1.0?mA, 0.8?mA, 0.5?mA and 0.3?mA. We conclude that the technique for automating the current intensity update, using accelerometer and/or electromyography, is satisfactory. Furthermore, we conclude that the use of the accelerometer alone is sufficient for detection of muscle contraction.     

Moderate-to-vigorous physical activity and the risk of stroke recurrence in patients with a history of minor ischemic stroke in Japan: a retrospective analysis

Background: Physical activity (PA) is beneficial for stroke prevention; in particular, moderate-to-vigorous physical activity (MVPA). However, few studies have investigated its relationship with recurrent ischemic stroke (RIS).

Objectives: To clarify the relationship between MVPA and RIS and the burden of risk factors after a first-ever ischemic stroke.

Methods: A total of 45 outpatients (mean age 67.1 ± 10.2 years) who had previously experienced a transient ischemic attack or a minor non-cardioembolic ischemic stroke at a single hospital in Japan (mean 6.4 ± 4.2 years previously), were enrolled between March and June 2016. All patients wore an accelerometer around their hips for 10 days, and their percentage body fat (%BF) and visceral fat level (VFL) were measured by bioelectrical impedance. Retrospective information about the history of RIS and risk factors (blood pressure, lipoprotein cholesterol and estimated glomerular filtration rate) were extracted from the clinical records. Binary logistic regression models were used to estimate the relevance of the RIS history to MVPA and potential risk factors such as sociodemographic and clinical variables (obesity, smoking and hypertension).

Results: RIS occurred in 9 patients; they had significantly higher VFL (p = 0.007) and %BF (p = 0.007) values and lower MVPA (p = 0.011) values than patients without recurrence. A multivariate analysis of these factors indicated that age, VFL and MVPA were signi?cant independent predictors of RIS.

Conclusions: Patients with a history of mild ischemic stroke had low MVPA and high VFL values, which together may be a risk factor for RIS.     

Circulating leptin levels are associated with physical activity or physical fitness in Japanese

Objective

The aim of this study was to evaluate the link between circulating leptin levels and physical activity and/or physical fitness in apparently healthy Japanese.

Methods

A total of 85 men and 111 women who were not taking any medication were enrolled in this cross-sectional study. Circulating leptin levels, physical activity measured by tri-axial accelerometers and peak oxygen uptake were evaluated. We also assessed anthropometric data, blood pressure, blood examinations and energy intake.

Results

Circulating leptin levels were 3.2 ± 2.3 ng/mL in men and 5.9 ± 3.8 ng/mL in women. Circulating leptin levels were significantly and positively correlated with body weight, body mass index, abdominal circumference, insulin and the homeostasis model assessment index, and significantly and negatively correlated with peak oxygen uptake in both sexes. Stepwise multiple regression showed that peak oxygen uptake in men and physical activity evaluated by \(\sum {\left[ {{\text{metabolic equivalents }} \times \rm h {\text{ per week}}({\text{METs}}\;\;h/w)} \right]}\) in women were determinant factors for circulating leptin levels after adjusting for confounding factors.     

What happens before the first step? A New Approach to Quantifying Gait Initiation Using a Wearable Sensor

BackgroundWalking is a volitional behavior that requires planning and initiation before a step is observed. Following a signal to begin walking, studies of gait initiation in specialized labs have identified three phases that occur during the transition from a standing position via anticipatory postural adjustment (APA) to the first step. Routine instrumented gait testing outside of the laboratory setting focuses on gait execution and does not include gait initiation measures.Research questionCan a single IMU sensor be used for performing gait initiation evaluations outside the lab?MethodsWe recorded walking in young (N = 41) and older (N = 26) adults using an instrumented gait mat while they were wearing a 3D accelerometer on their lower back. Subjects were instructed to begin walking following an auditory signal. An algorithm was developed to extract the following measures from the acceleration signal: gait initiation time, measured from the start of the auditory cue to begin walking and ends at the heel-strike of the swing leg, time-to-APA (reaction time), APA duration and swing time (execution of the first step).ResultsIntraclass correlation coefficient analysis showed good to excellent agreement between gait initiation metrics obtained with the gait mat and the wearable sensor (mean 0.88, range [0.75-0.96]). Except for swing time, all measures were longer in the older subjects, compared to the young adults (p < 0.01).SignificanceExtracting gait initiation measures from routine instrumented gait testing may facilitate studies that can better determine the extent to which impaired gait planning and execution contribute to mobility impairments.     

Functional parcellation of the human primary somatosensory cortex to natural touch

Despite the significance of human touch, brain responses to interpersonal manual touch have been rarely investigated. We used functional magnetic resonance imaging to study brain activity in eight healthy adults whose left hand was touched by two individuals, in separate runs and in 20‐s blocks, either by holding, smoothing, or poking. Acceleration was measured from both the subject's and the touching person's hands for postimaging control of the stimuli. Independent component analysis of the functional magnetic resonance imaging data unraveled three functional networks involving the primary somatosensory cortex (SI). One network comprised the contralateral and another the ipsilateral Brodmann area 3. The third network included area 2 bilaterally, left‐hemisphere middle temporal gyrus and dorsolateral prefrontal regions, ventral prefrontal cortices bilaterally, and middle cingulate cortex. The response shapes and polarities varied between the three networks. The contralateral area 3 differentiated the responses between the three types of touch stimuli, and the response magnitudes depended on the variability of the touch within each block. However, the responses of the other two networks were strikingly similar to all stimuli. The subjects' reports on the pleasantness of the touch did not correlate with the characteristics of the SI responses. These findings imply area‐specific processing of the natural human touch in three networks including the SI cortex, with only area 2 connected to a functional network of brain areas that may support social interaction.     

An evaluation of data processing when using the ActiGraph GT3X accelerometer in non-ambulant children and adolescents with cerebral palsy

Purpose

To evaluate vertical acceleration, vector magnitude, non-wear time, valid day classifications, and valid period classifications in the data processing phase when using the ActiGraph GT3X accelerometer in non-ambulant children and adolescents with cerebral palsy (CP).

Material and Methods

Accelerometer data retrieved from 33 non-ambulant children and adolescents (4–17 years) with CP were analysed. Comparisons of (i) vertical acceleration versus vector magnitude, (ii) two different non-wear times, (iii) three different settings to classify a day as valid and (iv) two different settings to classify a period as valid were made.

Results and Conclusions

Vector magnitude and a non-wear time of at least 90 consecutive minutes statistically significantly increased minutes recorded per day, especially for sedentary time. There was a statistically significant difference in numbers of valid days depending on time criteria set to determine a valid day, whereas there was no statistically significant difference in valid periods using 3 compared to 4 days. This study suggests using the pre-settings in ActiLife; vector magnitude, non-wear time of 90 consecutive minutes, 500 min recorded per day with periods of at least 3 valid days when assessing physical activity objectively by the ActiGraph GT3X accelerometer in non-ambulant children and adolescents with CP.     

基于MEMS传感器的可穿戴式老年人跌倒监测系统的设计

为了缩短老年人跌倒后的救助时间和提高安全保障,我们设计了一种基于加速度和角速度传感器的跌倒监测装置。该装置结合机械微电子系统(microelectro mechanical system,MEMS)传感器、数字信号处理及无线传输技术应用于智能手机上。为区分人体跌倒事件和日常行为,结合人体三轴加速度和角速度联合对跌倒事件进行判断,通过大量实验选取合适阈值。针对老年人的生活特点,数据通过蓝牙装置发送至手机上进行处理,通过手机语音报警、手机GPS定位系统和短信通知医院和用户监护人,使得老年人跌倒后能够在第一时间获得救治,减小伤害。经过大量的实验测试结果统计,相比较于传统的三轴加速度判断跌倒事件,结合三轴加速度和加速度联合判断使该系统的准确率从84.29%提高至100%。结果表明:基于MEMS传感器的可穿戴式跌倒监测系统具有便捷、准确、功耗低的特点,能够准确监测出跌倒事件并进行报警。