Evaluating the Effect of Activity and Environment on Fall Risk in a Paradigm-Depending Laboratory Setting: Protocol for an Experimental Pilot Study.

BACKGROUND: Knowledge about the causal factors leading to falls is still limited, and fall prevention interventions urgently need to be more effective to limit the otherwise increasing burden caused by falls in older people. To identify individual fall risk, it is important to understand the complex interplay of fall-related factors. Although fall events are common, they are seldom observed, and fall reports are often biased. Due to the rapid development of wearable inertial sensors, an objective approach to capture fall events and the corresponding circumstances is provided. OBJECTIVE: The aim of this work is to operationalize a prototypical dynamic fall risk model regarding 4 ecologically valid real-world scenarios (opening a door, slipping, tripping, and usage of public transportation). We hypothesize that individual fall risk is associated with an interplay of intrinsic risk factors, activity, and environmental factors that can be estimated by using data measured within a laboratory simulation setting. METHODS: We will recruit 30 community-dwelling people aged 60 years or older. To identify several fall-related intrinsic fall risk factors, appropriate clinical assessments will be selected. The experimental setup is adaptable so that the level of fall risk for each activity and each environmental factor is adjustable. By different levels of difficulty, the effect on the risk of falling will be investigated. An 8-camera motion tracking system will be used to record absolute body motions and limits of stability. All laboratory experiments will also be recorded by inertial sensors (L5, dominant leg) and video camera. Logistic regression analyses will be used to model the association between risk factors and falls. Continuous fall risk will be modeled by generalized linear regression models using margin of stability as outcome parameter. RESULTS: The results of this project will prove the concept and establish methods to further use the dynamic fall risk model. Recruitment and measurement initially began in October 2020 but were halted because of the COVID-19 pandemic. Recruitment and measurements recommenced in October 2022, and by February 2023, a total of 25 of the planned 30 subjects have been measured. CONCLUSIONS: In the field of fall prevention, a more precise fall risk model will have a significant impact on research leading to more effective prevention approaches. Given the described burden related to falls and the high prevalence, considerable improvements in fall prevention will have a significant impact on individual quality of life and also on society in general by reducing institutionalization and health care costs. The setup will enable the analysis of fall events and their circumstances ecologically valid in a laboratory setting and thereby will provide important information to estimate the individual instantaneous fall risk. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/46930.

Walking in high-risk settings: do older adults still prioritize gait when distracted by a cognitive task?

When a cognitive and a motor task like walking or keeping one's balance are performed concurrently, performance usually deteriorates. Older adults have often been shown to prioritize their motor performance in such dual-task situations, possibly to protect themselves from falls. The current study investigates whether these prioritization behaviors can still be observed when several challenges are combined. Younger (20-30 years old) and older adults (60-70 years old; n = 24 in each group) were asked to walk through virtual environments with and without a cognitive load (3-back task). Walking difficulty was increased by walking on an elevated surface or on a narrow as opposed to a broad track, or both. Walking instructions emphasized speed and accuracy (avoiding missteps). No instruction was given concerning which performance dimension should be prioritized during dual-task trials. Participants decreased their 3-back performance while walking. Younger adults maintained their walking speed on elevated surfaces and were able to keep the number of missteps low, even when walking on a narrow track while performing the cognitive task. Older adults increased their walking speed on elevated relative to even surfaces and committed more missteps under cognitive load. Results suggest that task prioritization might fail in healthy older adults if several challenges are combined in high-risk settings.

Adult age differences in familiarization to treadmill walking within virtual environments.

We assessed age-related differences in adults in familiarization to treadmill walking within virtual environments (VE), and examined whether treadmill walking after familiarization resembles overground walking. Seventeen younger and 17 older adults walked at preferred speed on an overground walkway and afterwards walked at the same speed for 20 min on a treadmill coupled to a VE. A motion capture system was used to measure spatio-temporal gait parameters. On the treadmill, both younger and older adults initially displayed decreased step length and increased step width, cadence, and time in double support relative to overground walking. Except for time in double support, step characteristics approached overground walking-behavior with a negatively accelerated trend. After 15 min of treadmill walking, changes became minor corresponding to less than 1% deviations to individuals' overground walking. At the end of familiarization, average differences in step length, cadence, and double support relative to overground walking were reduced to less than 5 percent in both age groups. For step width, younger adults approximated overground walking after 20 min more closely than older adults, probably reflecting larger initial differences between treadmill and overground walking among older adults. We conclude (a) that 20 min of familiarization to treadmill walking in a VE are sufficient to reach stable walking patterns resembling those observed in overground walking, but that some differences between the two settings remain, especially in older adults; (b) that sufficient familiarization to the treadmill is needed to ascertain the validity and generalizability of comparisons between younger and older adults.

Interacting effects of cognitive load and adult age on the regularity of whole-body motion during treadmill walking.

We investigated effects of concurrent cognitive task difficulty (n-back) on the regularity of whole-body movements during treadmill walking in women and men from 3 age groups (20-30, 60-70, and 70-80 years old). Using principal component analysis of individual gait patterns, we separated main (regular) from residual (irregular) components of whole-body motion. Proportion of residual variance (RV) was used as an index of gait irregularity. The gait in all age groups became more regular (reduced RV) upon introduction of a simple cognitive task (1-back), relative to walking without a concurrent cognitive task. In contrast, parametrically increasing working memory load from 1-back to 4-back led to age-differential effects, with gait patterns becoming more regular in those 20-30 years old, becoming less regular in those 70-80 years old, and showing no significant effects in those 60-70 years old. Our results support the dual-process account of sensorimotor-cognitive interactions (O. Huxhold, S.-C. Li, F. Schmiedek, and U. Lindenberger, 2006), with age-general effects of internal versus external attentional focus and age-specific effects of resource competition with increasing cognitive task difficulty.

Psychological principles of successful aging technologies: a mini-review.

Based on resource-oriented conceptions of successful lifespan development, we propose three principles for evaluating assistive technology: (a) net resource release; (b) person specificity, and (c) proximal versus distal frames of evaluation. We discuss how these general principles can aid the design and evaluation of assistive technology in adulthood and old age, and propose two technological strategies, one targeting sensorimotor and the other cognitive functioning. The sensorimotor strategy aims at releasing cognitive resources such as attention and working memory by reducing the cognitive demands of sensory or sensorimotor aspects of performance. The cognitive strategy attempts to provide adaptive and individualized cuing structures orienting the individual in time and space by providing prompts that connect properties of the environment to the individual's action goals. We argue that intelligent assistive technology continuously adjusts the balance between 'environmental support' and 'self-initiated processing' in person-specific and aging-sensitive ways, leading to enhanced allocation of cognitive resources. Furthermore, intelligent assistive technology may foster the generation of formerly latent cognitive resources by activating developmental reserves (plasticity). We conclude that 'lifespan technology', if co-constructed by behavioral scientists, engineers, and aging individuals, offers great promise for improving both the transition from middle adulthood to old age and the degree of autonomy in old age in present and future generations.

Quantitative and qualitative sex differences in spatial navigation.

We examined sex differences in spatial navigation performance using an ecologically relevant experimental paradigm in which virtual maze-like museums are projected in front of a treadmill. Thirty-two 20-30-year-old adults (16 women/16 men) performed a way-finding task in city-block (straight corridors) or variable (irregular corridors) topographies while walking on the treadmill. Sex differences in spatial navigation performance were reduced in variable topographies, suggesting less reliance on spatial relational learning among women. Also, spatial geometric knowledge of the mazes continued to be higher in men after all participants had attained perfect place-finding performance. Results indicate that sex differences in spatial navigation performance are modulated by interactions between environmental demands and sex differences in spatial processing.

Environmental topography and postural control demands shape aging-associated decrements in spatial navigation performance.

This study tests the hypothesis that aging-induced cognitive permeation of sensorimotor functions contributes to adult age differences in spatial navigation performance. Virtual maze-like museums were projected in front of a treadmill. Sixteen 20-30-year-old men and sixteen 60-70-year-old men performed a way-finding task in city-block or variable topographies while walking with or without support. Walking support attenuated age-related decrements in navigational learning. Navigation load increased trunk-angle variability for older adults only. Age differences in spatial knowledge persisted despite perfect place-finding performance. City-block topography was easier than variable topography for younger adults only, indicating age-related differences in reliance on spatial relational learning. Attempts at supporting older adults' navigation performance should consider sensorimotor/cognitive interactions and qualitative differences in navigational activity.