Brain and brawn in balance: Central processing speed and muscle torque development speed are independently associated with the ability to recover balance with feet-in-place

BACKGROUND

Stepping thresholds, i.e. the maximum perturbation one can withstand without taking a step, predict falls in older people. This ability requires fast central processing of sensory information followed by rapid execution of adequate motor responses, both of which are affected by age. However, there is limited evidence on their combined effect on stepping thresholds.

RESEARCH QUESTION

Are cognitive and motor speeds important for stepping thresholds and do they interact, allowing for compensation?

METHODS

Two-hundred forty-two people (mean age: 80 years, standard deviation 4; 110 women) underwent a series of waist-pulls of increasing magnitude to assess stepping thresholds in anterior, posterior and mediolateral directions. Cognitive function was assessed as simple hand reaction time and trail making test performance, and muscle function was assessed as isometric peak and rate of torque development of dominant leg muscles. Principal component analysis reduced these variables to four factors: peak muscle strength, muscle torque development speed (motor speed), executive function and central processing speed (cognitive speed). These factors were used in univariable and multivariable regression models to determine their association with stepping thresholds.

RESULTS

Faster central processing speed (beta:2.69; 95 %CI:1.49-3.88) and faster muscle torque development speed (beta:2.60, 95 %CI:0.63-4.57) were associated with higher stepping thresholds. These associations remained in a multivariable model. No interaction was found between cognitive and motor speed on stepping thresholds (p = 0.602).

SIGNIFICANCE

Central processing speed and muscle torque development speed affect stepping thresholds independently from each other and may both be important age-related motor impairment targets for preventing falls in older people.

Protocol of a 12-week eHealth programme designed to reduce concerns about falling in community-living older people: Own Your Balance randomised controlled trial

INTRODUCTION

Concerns about falling (CaF) are common in older people and have been associated with avoidance of activities of daily life. Exercise designed to prevent falls can reduce CaF, but the effects are usually short-lived. Cognitive behavioural therapy (CBT) can reduce CaF for longer but is not readily available in the community and unlikely to prevent falls. A multidomain intervention that combines CBT, motivational interviewing and exercise could be the long-term solution to treat CaF and reduce falls in older people with CaF. This paper describes the design of a randomised controlled trial to test the effectiveness of two different 12 week self-managed eHealth programmes to reduce CaF compared with an active control.

METHODS

A total of 246 participants (82 per group) aged 65 and over, with substantial concerns about falls or balance will be recruited from the community. They will be randomised into: (1) myCompass-Own Your Balance (OYB) (online CBT programme) intervention or (2) myCompass-OYB plus StandingTall intervention (an eHealth balance exercise programme), both including motivational interviewing and online health education or (3) an active control group (online health education alone). The primary outcome is change in CaF over 12 months from baseline of both intervention groups compared with control. The secondary outcomes at 2, 6 and 12 months include balance confidence, physical activity, habitual daily activity, enjoyment of physical activity, social activity, exercise self-efficacy, rate of falls, falls health literacy, mood, psychological well-being, quality of life, exercise self-efficacy, programme adherence, healthcare use, user experience and attitudes towards the programme. An intention-to-treat analysis will be applied. The healthcare funder's perspective will be adopted for the economic evaluation if appropriate.

ETHICS AND DISSEMINATION

Ethical approval was obtained from the South Eastern Sydney Local Health District Human Research Ethics Committee (2019/ETH12840). Results will be disseminated via peer-reviewed journals, local and international conferences, community events and media releases.

TRIAL REGISTRATION NUMBER

ACTRN12621000440820.

Effects of a multicomponent physical activity programme, Mobility-Fit, compared with a standard care lower limb strengthening programme, to promote safe mobility among older adults in care facilities: protocol for a cluster randomised controlled trial

INTRODUCTION

Upper limb and core strength training is essential for older adults to safely perform daily activities. However, existing exercise programmes mainly focus on lower limb strength and are not designed or delivered to suit people with different functional capacities. This study describes the design of a two-arm cluster randomised controlled trial to examine the effects of a multicomponent physical activity (PA) programme, Mobility-Fit, on mobility and frailty in older adults living in care facilities.

METHODS AND ANALYSIS

160 older adults from 20 care facilities in Hong Kong will be recruited and randomised by care facilities (1:1) to an intervention or a control group. Participants in the intervention group will attend the Mobility-Fit programme, led by facility-based instructors, three times per week, 45 min per session, for 12 weeks, while the control group will participate in a standard care lower limb strengthening programme offered by the care facility. Participants will then be followed up for 9 months. Mobility-Fit comprises agility, postural coordination, balance and strength training, with suitable dosage based on participant's baseline physical and cognitive function. The primary outcomes encompass upper and lower limb strength, trunk stability, reaction time, mobility function and fall efficacy. Secondary outcomes comprise daily PA level and performance, frailty, cognitive function and quality of life. A repeated measures analysis of variance (ANOVA) and generalised estimating equation (GEE) will be used to examine changes in outcomes over time and between groups. Data will be analysed following the intention-to-treat principles. We will also evaluate programme implementation and health economics throughout the follow-up period.

ETHICS AND DISSEMINATION

Ethical approval was acquired in November 2022 from the Joint CUHK-NTEC Clinical Research Ethics Committee in Hong Kong (CREC-2022-459). Informed consent will be obtained from participants. The results of the study will be disseminated through peer-reviewed articles, conference presentations and social media.

TRIAL REGISTRATION NUMBER

ChiCTR2300072709.

Association of Prospective Falls in Older People With Ubiquitous Step-Based Fall Risk Parameters Calculated From Ambulatory Inertial Signals: Secondary Data Analysis

Background

In recent years, researchers have been advocating for the integration of ambulatory gait monitoring as a complementary approach to traditional fall risk assessments. However, current research relies on dedicated inertial sensors that are fixed on a specific body part. This limitation impacts the acceptance and adoption of such devices.

Objective

Our study objective is twofold: (1) to propose a set of step-based fall risk parameters that can be obtained independently of the sensor placement by using a ubiquitous step detection method and (2) to evaluate their association with prospective falls.

Methods

A reanalysis was conducted on the 1-week ambulatory inertial data from the StandingTall study, which was originally described by Delbaere et al. The data were from 301 community-dwelling older people and contained fall occurrences over a 12-month follow-up period. Using the ubiquitous and robust step detection method Smartstep, which is agnostic to sensor placement, a range of step-based fall risk parameters can be calculated based on walking bouts of 200 steps. These parameters are known to describe different dimensions of gait (ie, variability, complexity, intensity, and quantity). First, the correlation between parameters was studied. Then, the number of parameters was reduced through stepwise backward elimination. Finally, the association of parameters with prospective falls was assessed through a negative binomial regression model using the area under the curve metric.

Results

The built model had an area under the curve of 0.69, which is comparable to models exclusively built on fixed sensor placement. A higher fall risk was noted with higher gait variability (coefficient of variance of stride time), intensity (cadence), and quantity (number of steps) and lower gait complexity (sample entropy and fractal exponent).

Conclusions

These findings highlight the potential of our method for comprehensive and accurate fall risk assessments, independent of sensor placement. This approach has promising implications for ambulatory gait monitoring and fall risk monitoring using consumer-grade devices.

Fall risk stratification of community-living older people. Commentary on the world guidelines for fall prevention and management

The Task Force on Global Guidelines for Falls in Older Adults has put forward a fall risk stratification tool for community-dwelling older adults. This tool takes the form of a flowchart and is based on expert opinion and evidence. It divides the population into three risk categories and recommends specific preventive interventions or treatments for each category. In this commentary, we share our insights on the design, validation, usability and potential impact of this fall risk stratification tool with the aim of guiding future research.

Theoretical framework of concerns about falling in older people: the role of health literacy

Adherence and participation can be improved in health programs for older people with concerns about falling. While health literacy empowers older people to have greater control over their health, little is known about the extent to which health literacy influences health behaviours associated with concerns about falling in older people. This study aimed to synthesise current findings on health literacy, concerns about falling and falls to propose a multicomponent theoretical model on health literacy and concerns about falling. The model was developed based on a review of the literature, existing frameworks and models on health literacy and concerns about falling. Existing evidence on the relationship between health literacy and concerns about falling in older people is limited. Evidence from other research areas, however, shows that health literacy is closely related to many of the determinants of concerns about falling. More research is needed to clarify the impact of health literacy on intervention adherence and decision-making processes of older people with concerns about falling. Our model offers a novel perspective on the role of health literacy in health behaviours associated with concerns about falling, suggesting new research directions and providing insights for clinicians to consider health literacy when managing older patients with concerns about falling.

Feasibility, Reliability, and Safety of Remote Five Times Sit to Stand Test in Patients with Gastrointestinal Cancer

Background: To determine the feasibility, reliability, and safety of the remote five times sit to stand test (5STS) test in patients with gastrointestinal cancer. Methods: Consecutive adult patients undergoing surgical treatment for lower gastrointestinal cancer at a major referral hospital in Sydney between July and November 2022 were included. Participants completed the 5STS test both face-to-face and remotely, with the order randomised. Outcomes included measures of feasibility, reliability, and safety. Results: Of fifty-five patients identified, seventeen (30.9%) were not interested, one (1.8%) had no internet coverage, and thirty-seven (67.3%) consented and completed both 5STS tests. The mean (SD) time taken to complete the face-to-face and remote 5STS tests was 9.1 (2.4) and 9.5 (2.3) seconds, respectively. Remote collection by telehealth was feasible, with only two participants (5.4%) having connectivity issues at the start of the remote assessment, but not interfering with the tests. The remote 5STS test showed excellent reliability (ICC = 0.957), with limits of agreement within acceptable ranges and no significant systematic errors observed. No adverse events were observed within either test environment. Conclusions: Remote 5STS for the assessment of functional lower extremity strength in gastrointestinal cancer patients is feasible, reliable, and safe, and can be used in clinical and research settings.

Exploring Older Adults' Experiences of a Home-Based, Technology-Driven Balance Training Exercise Program Designed to Reduce Fall Risk: A Qualitative Research Study Within a Randomized Controlled Trial

BACKGROUND AND PURPOSE

With an aging population, falls have become an increasing public health concern. While face-to-face exercise programs have demonstrated efficacy in reducing falls, their effectiveness is hampered by low participation and adherence. Digital technologies are a novel and potentially effective method for delivering tailored fall prevention exercise programs to older adults. In addition, they may increase the reach, uptake, and sustainability of fall prevention programs. Therefore, understanding older adults' experiences of using technology-driven methods is essential. This study explored the user experience of StandingTall , a home-based fall prevention program delivered through a tablet computer.

METHODS

Fifty participants were recruited using purposive sampling, from a larger randomized controlled trial. Participants were selected to ensure maximum variability with respect to age, gender, experience with technology, and adherence to the program. Participants undertook a one-on-one structured interview. We followed an iterative approach to develop themes.

RESULTS AND DISCUSSION

Eight themes were identified. These fall under 2 categories: user experience and program design. Participants found StandingTall enjoyable, and while its flexible delivery facilitated exercise, some participants found the technology challenging. Some participants expressed frustration with technological literacy, but most demonstrated an ability to overcome these challenges, and learn a new skill. Older adults who engaged in a technology-driven fall prevention program found it enjoyable, with the flexibility provided by the online delivery central to this experience. While the overall experience was positive, participants expressed mixed feelings about key design features. The embedded behavior change strategies were not considered motivating by most participants. Furthermore, some older adults associated the illustrated characters with gender-based stereotypes and negative views of aging, which can impact on motivation and preventive behavior.

CONCLUSION

This study found digital technologies are an effective and enjoyable method for delivering a fall prevention program. This study highlights that older adults are interested in learning how to engage successfully with novel technologies.

Responsiveness of Daily Life Gait Quality Characteristics over One Year in Older Adults Who Experienced a Fall or Engaged in Balance Exercise

Gait quality characteristics obtained from daily-life accelerometry are clinically relevant for fall risk in older adults but it is unknown whether these characteristics are responsive to changes in gait quality. We aimed to test whether accelerometry-based daily-life gait quality characteristics are reliable and responsive to changes over one year in older adults who experienced a fall or an exercise intervention. One-week trunk acceleration data were collected from 522 participants (65-97 years), at baseline and after one year. We calculated median values of walking speed, regularity (sample entropy), stability (logarithmic rate of divergence per stride), and a gait quality composite score, across all 10-s gait epochs derived from one-week gait episodes. Intraclass correlation coefficients (ICC) and limits of agreement (LOA) were determined for 198 participants who did not fall nor participated in an exercise intervention during follow-up. For responsiveness to change, we determined the number of participants who fell (n = 209) or participated in an exercise intervention (n = 115) that showed a change beyond the LOA. ICCs for agreement between baseline and follow-up exceeded 0.70 for all gait quality characteristics except for vertical gait stability (ICC = 0.69, 95% CI [0.62, 0.75]) and walking speed (ICC = 0.68, 95% CI [0.62, 0.74]). Only walking speed, vertical and mediolateral gait stability changed significantly in the exercisers over one year but effect sizes were below 0.2. The characteristic associated with most fallers beyond the LOA was mediolateral sample entropy (4.8% of fallers). For the exercisers, this was gait stability in three directions and the gait quality composite score (2.6% of exercisers). The gait quality characteristics obtained by median values over one week of trunk accelerometry were not responsive to presumed changes in gait quality after a fall or an exercise intervention in older people. This is likely due to large (within subjects) differences in gait behaviour that participants show in daily life.

Circumstances of Falls During Sit-to-Stand Transfers in Older People: A Cohort Study of Video-Captured Falls in Long-Term Care

OBJECTIVE

To characterize the circumstances of falls during sit-to-stand transfers in long-term care (LTC), including the frequency, direction, stepping and grasping responses, and injury risk, based on video analysis of real-life falls.

DESIGN

Cohort study.

SETTING

LTC.

PARTICIPANTS

We analyzed video footage of 306 real-life falls by 183 LTC residents that occurred during sit-to-stand transfers, collected from 2007 to 2020. The mean age was 83.7 years (SD=9.0 years), and 93 were female (50.8%).

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURES

We used Generalized Estimating Equations to test for differences in the odds that a resident would fall at least once during the rising vs stabilization phases of sit-to-stand and to test the association between the phase of the transfer when the fall occurred (rising vs stabilization) and the following outcomes: (1) the initial fall direction; (2) the occurrence, number, and direction of stepping responses; (3) grasping of environmental supports; and (4) documented injury.

RESULTS

Falls occurred twice as often in the rising phase than in the stabilization phase of the transfer (64.0% and 36.0%, respectively). Falls during rising were more often directed backward, while falls during stabilization were more likely to be sideways (odds ratio [OR]=1.95; 95% confidence interval [CI]=1.07-3.55). Falls during rising were more often accompanied by grasping responses, while falls during stabilization were more likely to elicit stepping responses (grasping: OR=0.30; 95% CI=0.14-0.64; stepping: OR=8.29; 95% CI=4.54-15.11). Injuries were more likely for falls during the stabilization phase than the rising phase of the transfer (OR=1.73; 95% CI=1.04-2.87).

CONCLUSION

Most falls during sit-to-stand transfers occurred from imbalance during the rising phase of the transfer. However, falls during the subsequent stabilization phase were more likely to cause injury.

Quality Output Checklist and Content Assessment (QuOCCA): a new tool for assessing research quality and reproducibility

Research must be well designed, properly conducted and clearly and transparently reported. Our independent medical research institute wanted a simple, generic tool to assess the quality of the research conducted by its researchers, with the goal of identifying areas that could be improved through targeted educational activities. Unfortunately, none was available, thus we devised our own. Here, we report development of the Quality Output Checklist and Content Assessment (QuOCCA), and its application to publications from our institute's scientists. Following consensus meetings and external review by statistical and methodological experts, 11 items were selected for the final version of the QuOCCA: research transparency (items 1-3), research design and analysis (items 4-6) and research reporting practices (items 7-11). Five pairs of raters assessed all 231 articles published in 2017 and 221 in 2018 by researchers at our institute. Overall, the results were similar between years and revealed limited engagement with several recommended practices highlighted in the QuOCCA. These results will be useful to guide educational initiatives and their effectiveness. The QuOCCA is brief and focuses on broadly applicable and relevant concepts to open, high-quality, reproducible and well-reported science. Thus, the QuOCCA could be used by other biomedical institutions and individual researchers to evaluate research publications, assess changes in research practice over time and guide the discussion about high-quality, open science. Given its generic nature, the QuOCCA may also be useful in other research disciplines.

Economic evaluation of the e-Health StandingTall balance exercise programme for fall prevention in people aged 70 years and over

BACKGROUND

globally, falls and fall-related injuries are the leading cause of injury-related morbidity and mortality in older people. In our ageing society healthcare costs are increasing, therefore programmes that reduce falls and are considered value for money are needed.

OBJECTIVE

to complete an economic evaluation of an e-Health balance exercise programme that reduced falls and injurious falls in community-dwelling older people compared to usual care from a health and community-care funder perspective.

DESIGN

a within-trial economic evaluation of an assessor-blinded randomised controlled trial with 2 years of follow-up.

SETTING

StandingTall was delivered via tablet-computer at home to older community-dwelling people in Sydney, Australia.

PARTICIPANTS

five hundred and three individuals aged 70+ years who were independent in activities of daily living, without cognitive impairment, progressive neurological disease or any other unstable or acute medical condition precluding exercise.

MAIN OUTCOME MEASURES

cost-effectiveness was measured as the incremental cost per fall and per injurious fall prevented. Cost-utility was measured as the incremental cost per quality-adjusted life year (QALY) gained.

MAIN RESULTS

the total average cost per patient for programme delivery and care resource cost was $8,321 (standard deviation [SD] 18,958) for intervention participants and $6,829 (SD 15,019) for control participants. The incremental cost per fall prevented was $4,785 and per injurious fall prevented was $6,585. The incremental cost per QALY gained was $58,039 (EQ5D-5L) and $110,698 (AQoL-6D).

CONCLUSION

this evaluation found that StandingTall has the potential to be cost-effective in specific subpopulations of older people, but not necessarily the whole older population.

TRIAL REGISTRATION

ACTRN12615000138583.

Effects of the Mobility-Fit Physical Activity Program on Strength and Mobility in Older Adults in Assisted Living: A Feasibility Study

Physical activity programs focusing on fall prevention often overlook upper-limb strength, which is important for transferring, balance recovery, and arresting a fall. We developed and evaluated a physical activity program, Mobility-Fit for older adults in Assisted Living (AL) that includes upper-limb strengthening, agility, coordination, and balance exercises. Thirty participants (85 ± 6 years) were recruited from two AL facilities; 15 were assigned to Mobility-Fit (three times/week, 45 min/session for 12 weeks) and 15 maintained usual care. Twenty-two participants (11 in each group) completed the study. We compared outcome changes between groups and interviewed participants and staff to explore the effectiveness and feasibility of the program. Among participants who attended Mobility-Fit, knee extension strength increased by 6%, reaction time decreased by 16%, and five-time sit-to-stand duration decreased by 15%. Conversely, participants in the usual care group had a 6% decrease in handgrip strength. Changes of these outcomes were significantly different between two groups (p < 0.05). Participants enjoyed the program and staff suggested some changes to improve attendance. Our results indicate that Mobility-Fit is feasible to deliver and beneficial for older adults in AL and may guide future clinical trials to evaluate the effectiveness of upper limb strengthening on safe mobility of older adults in care facilities.

Association between health literacy and physical activity in older people: a systematic review and meta-analysis

Physical inactivity is common in older people and contributes to morbidity and mortality. Health literacy might play a role in motivating people to become or stay physically active. However, little is known about the influence of health literacy on physical activity in older people. This review aims to determine the association between health literacy and physical activity in older people. A systematic search was conducted in CINAHL, MEDLINE, PsychINFO and CENTRAL. Inclusion criteria: (i) community-dwelling people with an average age of ≥55 and (ii) reported on the association between health literacy and physical activity. Exclusion criteria: (i) population with a health condition and (ii) case study or qualitative study. Data were extracted independently by two reviewers. Risk of bias was assessed using the Downs and Black checklist. A meta-analysis was conducted using random-effects models with inverse variance. Thirteen articles were included in the review and five articles were selected for the meta-analysis. Older people with inadequate health literacy were 38% less likely than older people with adequate health literacy to report engaging in physical activity on ≥5 days per week [odds ratio = 0.62, 95% confidence interval (CI) 0.55-0.77]. Only two articles used activity monitors; the mean number of steps taken per day was not significantly different between older people with adequate and inadequate health literacy (standardized mean difference = -0.15, 95% CI -0.30 to 0.01). Physical activity could potentially be fostered by increasing health literacy and empowering older people to make beneficial health decisions.

The Iconographical Falls Efficacy Scale (IconFES) in community-dwelling older people-a longitudinal validation study

BACKGROUND

This study aimed to develop cut-points for the 30-item and 10-item Iconographical Falls Efficacy Scale (IconFES) in community-dwelling older people and evaluate the psychometric properties, including construct and predictive validity with respect to falls and reduced physical activity over 1 year.

METHODS

Eight hundred and one participants completed the IconFES and underwent physical, psychological and cognitive measures at baseline. Physical activity was recorded at baseline and 12 months using an activity monitor, and 1-year fall incidence was collected using monthly falls calendars.

RESULTS

Using receiver-operating characteristic curves and the Youden's index for history of falls, physiological fall risk and depressive symptoms, cut-points were defined to differentiate between low and high concern about falling (30-item: <53; 10-item: <19). For the 30-item IconFES, we additionally defined cut-points for low (≤40), moderate (41-58) and high (≥59) concern about falling. Groups based on these cut-points differed significantly: low coordinated stability, executive function and amount of daily walking, and high level of disability (30-item version) and female gender (low/high 30-item version). Although there were some inconsistencies across IconFES classifications, high concern about falling predicted having had multiple falls or multiple/injurious falls, low amount of daily walking and low movement intensity at 12 months.

CONCLUSIONS

The developed IconFES cut-points were sensitive to variables associated with concern about falling and predicted fall incidence and physical activity restriction after 12 months. Applying these cut-points appears useful to identify older people with high concern about falling, who are at higher risk of falls and activity curtailment.

Protocol of a 12-month multifactorial eHealth programme targeting balance, dual-tasking and mood to prevent falls in older people: the StandingTall+ randomised controlled trial

INTRODUCTION

Falls have a multifactorial aetiology, which may limit the effectiveness of the common approach of exercise as the sole intervention strategy. Multifactorial interventions could be more effective in people at high risk of falling; however, the focus of such interventions has traditionally been quite narrow. This paper describes the design of a randomised controlled trial that will evaluate the effectiveness of an eHealth programme, which addresses cumulative effects of key fall-risk factors across the triad of physical, affective and cognitive functions on falls in older people.

METHODS AND ANALYSIS

518 older people aged 65 years and over with high fall risk, defined as having a history of falls in the past 6 months, self-reported fear of falling or being aged 80 years or over, will be recruited via local advertisements, newsletters and presentations, and randomised to an intervention or health education control group. The intervention comprises balance exercise, cognitive-motor exercise and cognitive-behavioural therapy, with their dosage based on participant's baseline balance, executive function and mood. The primary outcome is the rate of falls in the 12 months after randomisation. Secondary outcomes at 6 and 12 months comprise programme adherence, healthcare use, physical activity, balance and mobility, cognitive function, psychological well-being, quality of life, health literacy and user experience and attitudes towards the programme. Data will be analysed following intention to treat to gauge real-world effectiveness. We will further determine complier averaged causal effects to correct for varying adherence and conduct economic analyses to gain insight into cost-effectiveness and cost-utility.

ETHICS AND DISSEMINATION

Ethical approval was obtained from the University of New South Wales (UNSW) Human Research Ethics Committee in December 2017. Outcomes will be disseminated via peer-reviewed articles, conference presentations, community events and media releases.

TRIAL REGISTRATION NUMBER

ACTRN12619000540112.

E-health StandingTall balance exercise for fall prevention in older people: results of a two year randomised controlled trial

OBJECTIVE

To test whether StandingTall, a home based, e-health balance exercise programme delivered through an app, could provide an effective, self-managed fall prevention programme for community dwelling older people.

DESIGN

Assessor blinded, randomised controlled trial.

SETTING

Older people living independently in the community in Sydney, Australia.

PARTICIPANTS

503 people aged 70 years and older who were independent in activities of daily living, without cognitive impairment, progressive neurological disease, or any other unstable or acute medical condition precluding exercise.

INTERVENTIONS

Participants were block randomised to an intervention group (two hours of StandingTall per week and health education; n=254) or a control group (health education; n=249) for two years.

MAIN OUTCOME MEASURES

The primary outcomes were the rate of falls (number of falls per person year) and the proportion of people who had a fall over 12 months. Secondary outcomes were the number of people who had a fall and the number who had an injurious fall (resulting in any injury or requiring medical care), adherence, mood, health related quality of life, and activity levels over 24 months; and balance and mobility outcomes over 12 months.

RESULTS

The fall rates were not statistically different in the two groups after the first 12 months (0.60 falls per year (standard deviation 1.05) in the intervention group; 0.76 (1.25) in the control group; incidence rate ratio 0.84, 95% confidence interval 0.62 to 1.13, P=0.071). Additionally, the proportion of people who fell was not statistically different at 12 months (34.6% in intervention group, 40.2% in control group; relative risk 0.90, 95% confidence interval 0.67 to 1.20, P=0.461). However, the intervention group had a 16% lower rate of falls over 24 months compared with the control group (incidence rate ratio 0.84, 95% confidence interval 0.72 to 0.98, P=0.027). Both groups had a similar proportion of people who fell over 24 months (relative risk 0.87, 95% confidence interval 0.68 to 1.10, P=0.239), but the proportion of people who had an injurious fall over 24 months was 20% lower in the intervention group compared with the control group (relative risk 0.80, 95% confidence interval 0.66 to 0.98, P=0.031). In the intervention group, 68.1% and 52.0% of participants exercised for a median of 114.0 min/week (interquartile range 53.5) after 12 months and 120.4 min/week (38.6) after 24 months, respectively. Groups remained similar in mood and activity levels. The intervention group had a 0.03 (95% confidence interval 0.01 to 0.06) improvement on the EQ-5D-5L (EuroQol five dimension five level) utility score at six months, and an improvement in standing balance of 11 s (95% confidence interval 2 to 19 s) at six months and 10 s (1 to 19 s) at 12 months. No serious training related adverse events occurred.

CONCLUSIONS

The StandingTall balance exercise programme did not significantly affect the primary outcomes of this study. However, the programme significantly reduced the rate of falls and the number of injurious falls over two years, with similar but not statistically significant effects at 12 months. E-health exercise programmes could provide promising scalable fall prevention strategies.

TRIAL REGISTRATION

ACTRN12615000138583.

Deep Learning for Activity Recognition in Older People Using a Pocket-Worn Smartphone

Activity recognition can provide useful information about an older individual's activity level and encourage older people to become more active to live longer in good health. This study aimed to develop an activity recognition algorithm for smartphone accelerometry data of older people. Deep learning algorithms, including convolutional neural network (CNN) and long short-term memory (LSTM), were evaluated in this study. Smartphone accelerometry data of free-living activities, performed by 53 older people (83.8 ± 3.8 years; 38 male) under standardized circumstances, were classified into lying, sitting, standing, transition, walking, walking upstairs, and walking downstairs. A 1D CNN, a multichannel CNN, a CNN-LSTM, and a multichannel CNN-LSTM model were tested. The models were compared on accuracy and computational efficiency. Results show that the multichannel CNN-LSTM model achieved the best classification results, with an 81.1% accuracy and an acceptable model and time complexity. Specifically, the accuracy was 67.0% for lying, 70.7% for sitting, 88.4% for standing, 78.2% for transitions, 88.7% for walking, 65.7% for walking downstairs, and 68.7% for walking upstairs. The findings indicated that the multichannel CNN-LSTM model was feasible for smartphone-based activity recognition in older people.

Sensorimotor, Cognitive, and Affective Functions Contribute to the Prediction of Falls in Old Age and Neurologic Disorders: An Observational Study

OBJECTIVE

To determine whether impairments across cognitive and affective domains provide additional information to sensorimotor deficits for fall prediction among various populations.

DESIGN

We pooled data from 5 studies for this observational analysis of prospective falls.

SETTING

Community or low-level care facility.

PARTICIPANTS

Older people (N=1090; 74.0±9.4y; 579 female); 500 neurologically intact (NI) older people and 3 groups with neurologic disorders (cognitive impairment, n=174; multiple sclerosis (MS), n=111; Parkinson disease, n=305).

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Sensorimotor function was assessed with the Physiological Profile Assessment, cognitive function with tests of executive function, affect with questionnaires of depression, and concern about falling with falls efficacy questionnaires. These variables were associated with fall incidence rates, obtained prospectively over 6-12 months.

RESULTS

Poorer sensorimotor function was associated with falls (incidence rate ratio [95% CI], 1.46 [1.28-1.66]). Impaired executive function was the strongest predictor of falls overall (2.91 [2.27-3.73]), followed by depressive symptoms (2.07 [1.56-2.75]) and concern about falling (2.02 [1.61-2.55]). Associations were similar among groups, except for a weaker relationship with executive impairment in NI persons and a stronger relationship with concern about falling in persons with MS. Multivariable analyses showed that executive impairment, poorer sensorimotor performance, depressive symptoms, and concern about falling were independently associated with falls.

CONCLUSIONS

Deficits in cognition (executive function) and affect (depressive symptoms) and concern about falling are as important as sensorimotor function for fall prediction. These domains should be included in fall risk assessments for older people and clinical groups.

Association between Daily-Life Gait Quality Characteristics and Physiological Fall Risk in Older People

Gait quality characteristics obtained from accelerometry during daily life are predictive of falls in older people but it is unclear how they relate to fall risk. Our aim was to test whether these gait quality characteristics are associated with the severity of fall risk. We collected one week of trunk accelerometry data from 279 older people (aged 65–95 years; 69.5% female). We used linear regression to investigate the association between six daily-life gait quality characteristics and categorized physiological fall risk (QuickScreen). Logarithmic rate of divergence in the vertical (VT) and anteroposterior (AP) direction were significantly associated with the level of fall risk after correction for walking speed (both p < 0.01). Sample entropy in VT and the mediolateral direction and the gait quality composite were not significantly associated with the level of fall risk. We found significant differences between the high fall risk group and the very low- and low-risk groups, the moderate- and very low-risk and the moderate and low-risk groups for logarithmic rate of divergence in VT and AP (all p ≤ 0.01). We conclude that logarithmic rate of divergence in VT and AP are associated with fall risk, making them feasible to assess the physiological fall risk in older people.

Magnitude, symmetry and attenuation of upper body accelerations during walking in women: The role of age, fall history and walking surface

OBJECTIVES

The present experiment examined the role of age and fall history in upper body accelerations when walking on an even and on an uneven surface.

STUDY DESIGN

An observational cross-sectional study.

MAIN OUTCOME MEASURES

The magnitude (root mean square [RMS]), symmetry (harmonic ratio) and attenuation (attenuation coefficient) of upper body accelerations were quantified as primary outcomes; gait spatiotemporal parameters were measured as secondary outcomes.

METHODS

Twenty young adults (mean ± SD age: 29.00 ± 4.51 yrs), 20 older non-fallers (66.60 ± 5.43 yrs) and 20 older fallers (68.55 ± 4.86 yrs) walked on an even and on an uneven surface, while wearing four accelerometers attached to the forehead, pelvis, right and left shanks.

RESULTS

Older fallers exhibited increased RMS acceleration in the mediolateral direction at the pelvis level compared with young adults when walking on the even surface (0.18 ± 0.04 vs. 0.14 ± 0.02, respectively), whereas walking on an uneven surface was associated with reduced magnitude of acceleration in older fallers (0.19 ± 0.04) compared with non-fallers (0.23 ± 0.04) and young adults (0.22 ± 0.03). Among other changes, walking on the uneven surface diminished pelvis-to-head attenuation in the mediolateral direction in older fallers (38.07 ± 14.51) compared with non-fallers (50.96 ± 11.03) and young adults (62.62 ± 8.21; all ps<0.05).

CONCLUSIONS

Reduced mediolateral accelerations in older fallers when walking on the uneven surface can be interpreted as a compensatory mechanism to preserve stability through increased body stiffness. Reduced postural flexibility in the frontal plane compromises the central role of the trunk in minimizing the impact of gait-related oscillations to the head, as evidenced by reduced mediolateral attenuation in older fallers.

The effects of cognitive-motor training interventions on executive functions in older people: a systematic review and meta-analysis

Background

Ageing is associated with physical and cognitive decline, affecting independence and quality of life in older people. Recent studies show that in particular executive functions are important for daily-life function and mobility. This systematic review investigated the effectiveness of cognitive-motor training including exergaming on executive function (EF, set-shifting, working memory, inhibitory control) in healthy older people.

Methods

An electronic database search for randomised controlled trials (RCT), controlled clinical trials (CCT) and parallel group trials was performed using MEDLINE, EMBASE, and PsychINFO following PRISMA guidelines. Inclusion criteria were: (1) community-dwelling participants > 60 years without a medical condition or medical treatment, (2) reporting at least one cognitive-motor intervention while standing or walking, (3) use of dual-task interventions using traditional methods or modern technology to deliver a cognitive-motor task, (4) inclusion of at least one cognitive outcome. The PEDro scale was used for quality assessment.

Results

A total of 1557 studies were retrieved, of which 25 studies were included in this review. Eleven studies used a technology-based dual-task intervention, while 14 trials conducted a general cognitive-motor training. The age range of the cohort was 69 to 87 years. The interventions demonstrated positive effects on global cognitive function [mean difference 0.6, 95% CI 0.29–0.90] and inhibitory control [mean difference 0.61, 95% CI 0.28–0.94]. Effects were heterogeneous (I² range: 60–95) and did not remain after a sensitivity analysis. Processing speed and dual-task costs also improved, but meta-analysis was not possible.

Conclusion

Cognitive-motor and technology-based interventions had a positive impact on some cognitive functions. Dual-task interventions led to improvements of domains related global cognitive functions and inhibitory control. Likewise, technology-based exergame interventions improved functions related to processing speed, attentional and inhibitory control. Training interventions with a certain level of exercise load such as progression in difficulty and task specificity were more effective to gain task-related adaptations on cognitive functions.

Catch the ruler: concurrent validity and test-retest reliability of the ReacStick measures of reaction time and inhibitory executive function in older people

BACKGROUND

Reduced cognitive function, particularly executive function (EF), is associated with an increased risk of falling in older people. We evaluated the utility of the ReacStick test, a clinical test of reaction time, and inhibitory EF developed, for young athletes, for fall-risk assessment in older people.

AIMS

To evaluate the psychometric properties of ReacStick measures of reaction time and executive functioning in healthy community-dwelling older people.

METHODS

140 participants (aged 77 ± 5 years) underwent testing. Two test conditions-simple and inhibitory go/no-go-provided measures of reaction time, recognition load (difference in reaction time between conditions), and go/no-go accuracy. Concurrent validity was evaluated against the conventional tests of reaction time and EF (simple hand reaction time, trail-making test, and Stroop colour test). Discriminant ability was determined for fall-risk factors (age, gender, physiological profile assessment, and fall history). Test-retest reliability after 1 week was evaluated in 30 participants.

RESULTS

ReacStick reaction time correlated with tests of reaction time and EF, recognition load correlated with inhibitory EF, and go accuracy correlated with reaction time and inhibitory EF. No-go accuracy was not significantly correlated with any of the reaction time and EF tests. Test-retest reliability was good-to-excellent (ICC > 0.6) for all the outcomes. ReacStick reaction time discriminated between groups based on age, recognition load between genders, and no-go accuracy between retrospective fallers and non-fallers.

DISCUSSION

An unavoidable time pressure may result in complementary information to the traditional measures.

CONCLUSIONS

The ReacStick is a reliable test of reaction time and inhibitory EF in older people and could have value for fall-risk assessment.

Concern About Falling Is Associated With Gait Speed, Independently From Physical and Cognitive Function

BACKGROUND

Higher levels of concern about falling in older people have been associated with slower walking speed and an increased risk of falls. However, it is unclear whether this relationship is independent or confounded by other fall risk factors, such as physical and cognitive function.

OBJECTIVE

The aim of this study was to examine the effects of concern about falling on gait speed, adjusted for physiological fall risk and cognitive function.

DESIGN

This was an observational, cross-sectional study.

METHODS

A total of 204 community-dwelling older people aged 70 years or older were recruited from 2 sites (Germany, n = 94; Australia, n = 110). Walking speed was measured over 6 m under 4 conditions: preferred speed, fast speed, speed while carrying a tray (functional dual task), and speed while answering a question (cognitive dual task). The Falls Efficacy Scale-International was used to assess concern about falling, the Physiological Profile Assessment was used to assess physiological fall risk, and the Digit Symbol Substitution Test and Trail Making Test were used to assess attention and executive function.

RESULTS

Higher levels of concern about falling were associated with slower gait speed. Following adjustment for age, history of falls, and female sex, and further adjustment for physical and cognitive function, the association between concern about falling and walking speed remained significant, with a considerable effect size (standardized β = 0.18 ± 0.08; P = .037).

LIMITATIONS

The use of walking speed as a sole measure of gait was a limitation of this study.

CONCLUSIONS

Gait speed, especially under dual-task conditions, was affected by concern about falling. Concern about falling was the strongest predictor of gait speed under all 4 conditions and should be included in routine geriatric assessments.

The association between age and accelerometry-derived types of habitual daily activity: an observational study over the adult life span in the Netherlands

Background

Advances in sensor technology allow for objective and high-resolution monitoring of physical activity and sedentary behaviour. Novel epidemiological data is required to provide feedback on an individual’s habitual daily activity in comparison to peers and might eventually lead to refined physical activity guidelines.

Methods

We merged data of 762 people between 18 and 99 years of age, who all wore a DynaPort MoveMonitor accelerometer on their lower back during 1 week in daily-life, to provide insight into habitual types and durations of daily activities, and examine the association between age and physical activity and sedentary behaviour.

Results

We found associations between age and almost all activity outcomes. These associations suggested that physical activity declines and sedentary behaviour increases from the age of 50. We further describe an association with gender, with men walking more often in fewer but longer bouts and having fewer, longer bouts of sitting and standing.

Conclusions

These data provide a valuable reference and may call for more age- and gender-specific activity interventions.

Electronic supplementary material

The online version of this article (10.1186/s12889-018-5719-8) contains supplementary material, which is available to authorized users.

Deep Learning to Predict Falls in Older Adults Based on Daily-Life Trunk Accelerometry

Early detection of high fall risk is an essential component of fall prevention in older adults. Wearable sensors can provide valuable insight into daily-life activities; biomechanical features extracted from such inertial data have been shown to be of added value for the assessment of fall risk. Body-worn sensors such as accelerometers can provide valuable insight into fall risk. Currently, biomechanical features derived from accelerometer data are used for the assessment of fall risk. Here, we studied whether deep learning methods from machine learning are suited to automatically derive features from raw accelerometer data that assess fall risk. We used an existing dataset of 296 older adults. We compared the performance of three deep learning model architectures (convolutional neural network (CNN), long short-term memory (LSTM) and a combination of these two (ConvLSTM)) to each other and to a baseline model with biomechanical features on the same dataset. The results show that the deep learning models in a single-task learning mode are strong in recognition of identity of the subject, but that these models only slightly outperform the baseline method on fall risk assessment. When using multi-task learning, with gender and age as auxiliary tasks, deep learning models perform better. We also found that preprocessing of the data resulted in the best performance (AUC = 0.75). We conclude that deep learning models, and in particular multi-task learning, effectively assess fall risk on the basis of wearable sensor data.

The Association Between Fall Frequency, Injury Risk, and Characteristics of Falls in Older Residents of Long-Term Care: Do Recurrent Fallers Fall More Safely?

Background

Although a fall is a necessary prerequisite to a fall-related injury, previous studies suggest that frequent fallers are at lower injury risk for a given fall. We tested the hypotheses that differences in protective responses or the circumstances of falls underlie differences in injury risk with fall frequency.

Methods

We analyzed video footage of 897 falls experienced by 220 long-term care residents (mean age 82 ± 9 years) to identify the cause of imbalance, activity leading to falling, direction of fall initiation, balance recovery and fall protective responses, and occurrence of impact to the head or hip. We further obtained injury information from the facilities' fall registration. We used generalized estimating equation models to examine the association between quartiles of fall frequency, injury risk, and fall characteristics.

Results

Residents with the highest fall frequency group (Q4; ≥5.6 falls/year) were less likely to sustain an injury per fall. They were less likely to fall during walking and more likely to fall during stand-to-sit transfers. Residents in the lowest fall frequency group (Q1; <1.15 falls/year) were more likely to fall during walking, and walking was associated with an increased risk for injury.

Conclusion

When compared to less frequent fallers, more frequent fallers had a lower risk for injury per fall. This appeared to be explained by differences in the circumstances of falls, and not by protective responses. Injury prevention strategies in long-term care should target both frequent and infrequent fallers, as the latter are more mobile and apt to sustain injury.

Improved Prediction of Falls in Community-Dwelling Older Adults Through Phase-Dependent Entropy of Daily-Life Walking

Age and age-related diseases have been suggested to decrease entropy of human gait kinematics, which is thought to make older adults more susceptible to falls. In this study we introduce a new entropy measure, called phase-dependent generalized multiscale entropy (PGME), and test whether this measure improves fall-risk prediction in community-dwelling older adults. PGME can assess phase-dependent changes in the stability of gait dynamics that result from kinematic changes in events such as heel strike and toe-off. PGME was assessed for trunk acceleration of 30 s walking epochs in a re-analysis of 1 week of daily-life activity data from the FARAO study, originally described by van Schooten et al. (2016). The re-analyzed data set contained inertial sensor data from 52 single- and 46 multiple-time prospective fallers in a 6 months follow-up period, and an equal number of non-falling controls matched by age, weight, height, gender, and the use of walking aids. The predictive ability of PGME for falls was assessed using a partial least squares regression. PGME had a superior predictive ability of falls among single-time prospective fallers when compared to the other gait features. The single-time fallers had a higher PGME (p < 0.0001) of their trunk acceleration at 60% of their step cycle when compared with non-fallers. No significant differences were found between PGME of multiple-time fallers and non-fallers, but PGME was found to improve the prediction model of multiple-time fallers when combined with other gait features. These findings suggest that taking into account phase-dependent changes in the stability of the gait dynamics has additional value for predicting falls in older people, especially for single-time prospective fallers.

Fractional Stability of Trunk Acceleration Dynamics of Daily-Life Walking: Toward a Unified Concept of Gait Stability

Over the last decades, various measures have been introduced to assess stability during walking. All of these measures assume that gait stability may be equated with exponential stability, where dynamic stability is quantified by a Floquet multiplier or Lyapunov exponent. These specific constructs of dynamic stability assume that the gait dynamics are time independent and without phase transitions. In this case the temporal change in distance, d(t), between neighboring trajectories in state space is assumed to be an exponential function of time. However, results from walking models and empirical studies show that the assumptions of exponential stability break down in the vicinity of phase transitions that are present in each step cycle. Here we apply a general non-exponential construct of gait stability, called fractional stability, which can define dynamic stability in the presence of phase transitions. Fractional stability employs the fractional indices, α and β, of differential operator which allow modeling of singularities in d(t) that cannot be captured by exponential stability. The fractional stability provided an improved fit of d(t) compared to exponential stability when applied to trunk accelerations during daily-life walking in community-dwelling older adults. Moreover, using multivariate empirical mode decomposition surrogates, we found that the singularities in d(t), which were well modeled by fractional stability, are created by phase-dependent modulation of gait. The new construct of fractional stability may represent a physiologically more valid concept of stability in vicinity of phase transitions and may thus pave the way for a more unified concept of gait stability.

Characteristics of daily life gait in fall and non fall-prone stroke survivors and controls

BACKGROUND

Falls in stroke survivors can lead to serious injuries and medical costs. Fall risk in older adults can be predicted based on gait characteristics measured in daily life. Given the different gait patterns that stroke survivors exhibit it is unclear whether a similar fall-prediction model could be used in this group. Therefore the main purpose of this study was to examine whether fall-prediction models that have been used in older adults can also be used in a population of stroke survivors, or if modifications are needed, either in the cut-off values of such models, or in the gait characteristics of interest.

METHODS

This study investigated gait characteristics by assessing accelerations of the lower back measured during seven consecutive days in 31 non fall-prone stroke survivors, 25 fall-prone stroke survivors, 20 neurologically intact fall-prone older adults and 30 non fall-prone older adults. We created a binary logistic regression model to assess the ability of predicting falls for each gait characteristic. We included health status and the interaction between health status (stroke survivors versus older adults) and gait characteristic in the model.

RESULTS

We found four significant interactions between gait characteristics and health status. Furthermore we found another four gait characteristics that had similar predictive capacity in both stroke survivors and older adults.

CONCLUSION

The interactions between gait characteristics and health status indicate that gait characteristics are differently associated with fall history between stroke survivors and older adults. Thus specific models are needed to predict fall risk in stroke survivors.

Daily-Life Gait Quality as Predictor of Falls in Older People: A 1-Year Prospective Cohort Study

Falls can have devastating consequences for older people. We determined the relationship between the likelihood of fall incidents and daily-life behavior. We used wearable sensors to assess habitual physical activity and daily-life gait quality (in terms of e.g. stability, variability, smoothness and symmetry), and determined their predictive ability for time-to-first-and-second-falls. 319 older people wore a trunk accelerometer (Dynaport MoveMonitor, McRoberts) during one week. Participants further completed questionnaires and performed grip strength and trail making tests to identify risk factors for falls. Their prospective fall incidence was followed up for six to twelve months. We determined interrelations between commonly used gait characteristics to gain insight in their interpretation and determined their association with time-to-falls. For all data -including questionnaires and tests- we determined the corresponding principal components and studied their predictive ability for falls. We showed that gait characteristics of walking speed, stride length, stride frequency, intensity, variability, smoothness, symmetry and complexity were often moderately to highly correlated (r > 0.4). We further showed that these characteristics were predictive of falls. Principal components dominated by history of falls, alcohol consumption, gait quality and muscle strength proved predictive for time-to-fall. The cross-validated prediction models had adequate to high accuracy (time dependent AUC of 0.66–0.72 for time-to-first-fall and 0.69–0.76 for -second-fall). Daily-life gait quality obtained from a single accelerometer on the trunk is predictive for falls. These findings confirm that ambulant measurements of daily behavior contribute substantially to the identification of elderly at (high) risk of falling.

Do extreme values of daily-life gait characteristics provide more information about fall risk than median values?

Background

Gait characteristics estimated from daily-life trunk accelerations reflect gait quality and are associated with fall incidence in older adults. While associations are based on median values of these gait characteristics, their extreme values may reflect either high-risk situations or steady-state gait and may thus be more informative in relation to fall risk.

Objective

The objective of this study was to improve fall-risk prediction models by examining whether the use of extreme values strengthens the associations with falls.

Methods

Trunk acceleration data (Dynaport MoveMonitor) were collected from 202 older adults over a full week. From all walking episodes, we estimated the median and, as reliable estimates of the extremes, the 10th and 90th percentiles of gait characteristics, all over 10-second epochs. In addition, the amount of daily activities was derived from the acceleration data, and participants completed fall-risk questionnaires. Participants were classified as fallers based on one or more falls during 6 months of follow-up. Univariate analyses were performed to investigate whether associations with falls were stronger for the extremes than for the medians. Subsequently, three fall-risk models were compared: (1) using questionnaire data only, (2) adding the amount of activities and medians of gait characteristics, and (3) using extreme values instead of medians in the case of stronger univariate associations of the extremes.

Results

Stronger associations were found for the extreme characteristics reflecting high regularity, low frequency variability, and low local instability in anterior-posterior direction, for high symmetry in all directions and for low entropy in anterior-posterior and vertical directions. The questionnaire-only model improved significantly by adding activities and gait characteristics’ medians. Replacing medians by extremes with stronger associations did improve the fall prediction model, but not significantly.

Conclusions

Associations were stronger for extreme values, indicating “high gait quality” situations (ie, 10th and 90th percentiles in case of positive and negative associations, respectively) and not for “low gait quality” situations. This suggests that gait characteristics during optimal performance gait provide more information about the risk of falling than high-risk situations. However, their added value over medians in prediction is limited.

Identification of Fall Risk Predictors in Daily Life Measurements

Background. Gait characteristics extracted from trunk accelerations during daily life locomotion are complementary to questionnaire- or laboratory-based gait and balance assessments and may help to improve fall risk prediction. Objective. The aim of this study was to identify gait characteristics that are associated with self-reported fall history and that can be reliably assessed based on ambulatory data collected during a single week. Methods. We analyzed 2 weeks of trunk acceleration data (DynaPort MoveMonitor, McRoberts) collected among 113 older adults (age range, 65-97 years). During episodes of locomotion, various gait characteristics were determined, including local dynamic stability, interstride variability, and several spectral features. For each characteristic, we performed a negative binomial regression analysis with the participants’ self-reported number of falls in the preceding year as outcome. Reliability of gait characteristics was assessed in terms of intraclass correlations between both measurement weeks. Results. The percentages of spectral power below 0.7 Hz along the vertical and anteroposterior axes and below 10 Hz along the mediolateral axis, as well as local dynamic stability, local dynamic stability per stride, gait smoothness, and the amplitude and slope of the dominant frequency along the vertical axis, were associated with the number of falls in the preceding year and could be reliably assessed (all P < .05, intraclass correlation > 0.75). Conclusions. Daily life gait characteristics are associated with fall history in older adults and can be reliably estimated from a week of ambulatory trunk acceleration measurements.

Consistency of gait characteristics as determined from acceleration data collected at different trunk locations

Estimates of gait characteristics may suffer from errors due to discrepancies in accelerometer location. This is particularly problematic for gait measurements in daily life settings, where consistent sensor positioning is difficult to achieve. To address this problem, we equipped 21 healthy adults with tri-axial accelerometers (DynaPort MiniMod, McRoberts) at the mid and lower lumbar spine and anterior superior iliac spine (L2, L5 and ASIS) while continuously walking outdoors back and forth (20 times) over a distance of 20 m, including turns. We compared 35 gait characteristics between sensor locations by absolute agreement intra-class correlations (2, 1; ICC). We repeated these analyses after applying a new method for off-line sensor realignment providing a unique definition of the vertical and, by symmetry optimization, the two horizontal axes. Agreement between L2 and L5 after realignment was excellent (ICC>0.9) for stride time and frequency, speed and their corresponding variability and good (ICC>0.7) for stride regularity, movement intensity, gait symmetry and smoothness and for local dynamic stability. ICC values benefited from sensor realignment. Agreement between ASIS and the lumbar locations was less strong, in particular for gait characteristics like symmetry, smoothness, and local dynamic stability (ICC generally<0.7). Unfortunately, this lumbar-ASIS agreement did not benefit consistently from sensor realignment. Our findings show that gait characteristics are robust against limited repositioning error of sensors at the lumbar spine, in particular if our off-line realignment is applied. However, larger positioning differences (from lumbar positions to ASIS) yield less consistent estimates and should hence be avoided.

Toward ambulatory balance assessment: estimating variability and stability from short bouts of gait

Stride-to-stride variability and local dynamic stability of gait kinematics are promising measures to identify individuals at increased risk of falling. This study aimed to explore the feasibility of using these metrics in clinical practice and ambulatory assessment, where only a small number of consecutive strides are available. The concurrent validity and reliability were assessed compared to more continuous walking. Twenty young adults walked continuously for 500 m, as well as 36 bouts of 20 m while wearing an accelerometer (DynaPort MiniMod) on the trunk. Within-day reliability was high for stride time variability, mediolateral trunk variability and local dynamic stability, while between-day reliability was low for both variability estimates and moderate for local dynamic stability. Stride time variability and mediolateral trunk variability were increased when walking short bouts and did not correlate well with the longer walking trials. Local dynamic stability did correlate highly between the long and short bouts trials, and 15 bouts of eight strides appeared to be sufficient for valid estimation. These results imply task-specific differences and low reliability of variability estimates rendering them unsuitable for application to short bouts of gait, while local dynamic stability can be readily employed.

Sensitivity of trunk variability and stability measures to balance impairments induced by galvanic vestibular stimulation during gait

For targeted prevention of falls, it is necessary to identify individuals with balance impairments. To test the sensitivity of measures of variability, local stability and orbital stability of trunk kinematics to balance impairments during gait, we used galvanic vestibular stimulation (GVS) to impair balance in 12 young adults while walking on a treadmill at different speeds. Inertial sensors were used to measure trunk accelerations, from which variability in the medio-lateral direction and local and orbital stability were calculated. The short-term Lyapunov exponent and variability reflected the destabilizing effect of GVS, while the long-term Lyapunov exponent and Floquet multipliers suggested increased stability. Therefore, we concluded that only short-term Lyapunov exponents and variability can be used to asses stability of gait. In addition, to investigate the feasibility of using these measures in screening for fall risk, the presence or absence of GVS was predicted with variability and the short-term Lyapunov exponent. Predictions were good at all walking speeds, but best at preferred walking speed, with a correct classification in 83.3% of the cases.

Sensitivity of local dynamic stability of over-ground walking to balance impairment due to galvanic vestibular stimulation

Impaired balance control during gait can be detected by local dynamic stability measures. For clinical applications, the use of a treadmill may be limiting. Therefore, the aim of this study was to test sensitivity of these stability measures collected during short episodes of over-ground walking by comparing normal to impaired balance control. Galvanic vestibular stimulation (GVS) was used to impair balance control in 12 healthy adults, while walking up and down a 10 m hallway. Trunk kinematics, collected by an inertial sensor, were divided into episodes of one stroll along the hallway. Local dynamic stability was quantified using short-term Lyapunov exponents (λ_s), and subjected to a bootstrap analysis to determine the effects of number of episodes analysed on precision and sensitivity of the measure. λ_s increased from 0.50 ± 0.06 to 0.56 ± 0.08 (p = 0.0045) when walking with GVS. With increasing number of episodes, coefficients of variation decreased from 10 ± 1.3% to 5 ± 0.7% and the number of p values >0.05 from 42 to 3.5%, indicating that both precision of estimates of λ_s and sensitivity to the effect of GVS increased. λ_s calculated over multiple episodes of over-ground walking appears to be a suitable measure to calculate local dynamic stability on group level.