京都大学 / 0048 / 新制・課程博士 / 博士(人間健康科学) / 甲第19640号 / 人健博第32号 / 新制||人健||3(附属図書館) / 32676 / 京都大学大学院医学研究科人間健康科学系専攻 / (主査)教授 黒木 裕士, 教授 坪山 直生, 教授 黒田 知宏 / 学位規則第4条第1項該当 / Doctor of Human Health Sciences / Kyoto University / DFAM

No description available.

Walking Assist Exoskeletons are wearable devices that can allow individuals with mobility impairments to maintain their autonomy. The growing elderly population has benefited from these devices by receiving assistance at joints where their muscle function has declined. Typically, the primary objective of these exoskeletons has been to reduce the metabolic cost of walking, allowing users to walk for extended periods of time while reducing fatigue. However, this strategy does not directly address the growing concern that seniors are at an increased risk of falling and sustaining severe injuries due to falls. Gait and balance disorders are among the most common causes of falls in the elderly. As the Canadian population ages, it is increasingly important to investigate the musculoskeletal changes contributing to frontal-plane instability, as mediolateral and posterolateral falls are correlated with higher incidences of severe injuries. Specifically, the hip abductor and hip adductor muscles are essential in maintaining balance in the frontal plane, yet little research has been conducted on the effect of hip abduction-adduction exoskeleton assistance on the stability of elderly individuals. This thesis investigates the effect of introducing an assistive torque with a specific magnitude, timing, and location (i.e. applied to one or both legs) on the margin of stability of elderly individuals using the OpenSim biomechanics software. Simulations of four elderly subjects were conducted while the subjects stood in a quiet standing position with both feet on the ground. A lateral perturbation force of magnitude 5%, 10% or 15% of bodyweight was applied to the pelvis of each subject. The simulations were designed to provide elderly subjects with contralateral (i.e. the limb on the opposite side of the body as the perturbation), ipsilateral (i.e. the limb on the same side as the perturbation), or bilateral hip abduction-adduction assistive torque from a hip exoskeleton device after a perturbation force was applied to the pelvis. The simulated actuators mounted at the hip joints were massless, applied torque in the frontal plane, and could generate torque instantaneously based on user-defined inputs. The change in margin of stability was used to measure the effectiveness of each assistive strategy and for comparison across all subjects. The results of this study suggest that, as the perturbation magnitude increases, the hip abduction-adduction assistive exoskeleton should prioritize assistance applied to the contralateral limb. Regardless of the perturbation magnitude, each assistive strategy that was simulated (i.e. contralateral, ipsilateral and bilateral assistance) was able to improve the margin of stability. The greatest mean improvement on the margin of stability compared to the unassisted condition occurred when using the contralateral assistance strategy. For the 5%, 10% and 15% bodyweight perturbations, a contralateral assistance of 0.75 N·m/kg (torque normalized by the subject's mass) resulted in an improvement in the margin of stability of 13.1 ± 0.987 mm, 13.0 ± 0.946 mm and 13.1 ± 0.816 mm, respectively. The simulations also suggested that similar improvements on the margin of stability were experienced at smaller assistive torque magnitudes when the actuators provided torque to the body quicker following a perturbation. The results of this study can be used by exoskeleton designers to guide their decisions when developing abduction-adduction assistive exoskeletons that target mediolateral stability assistance in the elderly population.

Diabetes (DM) and hypertension (HTN) are prevalent chronic diseases among older adults. For example, in the U.S., 1 in 4 older adults have DM, 3 in 4 have HTN and 1 in 6 have DM and HTN. Moreover, each year, health care costs attributable to DM and HTN are estimated at $327 billion and $131 billion USD respectively. Both diseases also impose tremendous burden on the health and well-being of older adults. For example, gait speed (GS) is reduced in older adults with DM or HTN compared to older adults without DM or HTN. Gait speed is a powerful indicator of health status among older adults. Reduced GS predicts various adverse health outcomes including falls, frailty, cognitive impairment, reduced quality of life, hospitalization and even death. Moreover, adequate GS is required to safely execute daily activities. For example, GS of 1.14 m/s or faster is required to safely cross the street. Reduced GS in older adults with DM or HTN can partly be explained by multimorbidity (e.g., older adults with DM are at increased risk of developing HTN) as well as complications that are frequently associated with DM and HTN. For example, older adults with DM or HTN are at increased risk of developing peripheral artery disease, which causes reduced lower extremity muscle strength and pain, as well as retinopathy, which causes vision impairment. Additionally, older adults with DM are at increased risk of developing peripheral neuropathy, which causes pain and impaired balance. Although the physiological mechanisms of these complications are largely understood, research is needed to determine the extent to which these complications contribute to GS decline among older adults with DM, HTN or DM and HTN. The overarching objective of this thesis was to examine how multimorbidity patterns (i.e., types/combinations of chronic diseases), and sensory and motor impairments impact GS in older adults with DM, HTN or DM and HTN. This thesis also examined how GS changes over time (i.e., trajectories) in this population. This thesis is comprised of 3 manuscripts and was conducted using data from the National Health and Aging Trends Study (NHATS); a large, nationally representative sample of American older adults. Annual data collection began in 2011 and is ongoing. In 2015, the NHATS was replenished with approximately 50% new participants, to account for death and loss-to-follow-up. Therefore, data was analyzed in two cohorts: cohort A (individuals recruited in 2011) and cohort B (individuals recruited in 2015 and individuals recruited in 2011 who remained in the sample at the time of replenishment). In manuscript 1, latent class analysis was performed to identify multimorbidity patterns in older adults with DM, HTN or DM and HTN. Additionally, analysis of covariance (ANCOVA) was conducted to examine differences in GS among these multimorbidity patterns. This study identified a total of nine multimorbidity patterns in cohort A: two patterns in older adults with DM (low multimorbidity and cardiovascular-joint multimorbidity), three patterns in older adults with HTN (low multimorbidity, psychological multimorbidity and cardiovascular multimorbidity) and four patterns in older adults with DM and HTN (metabolic-cardiovascular-psychological-joint multimorbidity, metabolic-bone-joint multimorbidity, metabolic-cardiovascular-joint multimorbidity and metabolic multimorbidity). Additionally, this study identified a total of ten multimorbidity patterns in cohort B: two patterns in older adults with DM (low multimorbidity and joint multimorbidity), four patterns in older adults with HTN (cardiovascular-joint-respiratory multimorbidity, cardiovascular multimorbidity, psychological-joint multimorbidity and joint multimorbidity) and four patterns in older adults with DM and HTN (metabolic-cardiovascular-joint-respiratory multimorbidity, metabolic-psychological-joint multimorbidity, metabolic-bone-joint multimorbidity and metabolic-joint multimorbidity). Overall, multimorbidity patterns with larger numbers of chronic diseases patterns or patterns that included depression or anxiety were associated with the slowest GS. In manuscript 2, multinomial logistic regression was used to conduct state-based analyses which examined the relationship between impairments (i.e., hearing, and vision impairment, pain, balance, and lower extremity strength impairment) and GS transitions (i.e., fast to, intermediate walker, intermediate to slow walker etc.) in older adults with DM, HTN or DM and HTN. Balance and lower extremity strength impairment were associated with an increased risk of GS decline (i.e., transitioning from an intermediate to slow walker). Moreover, older adults with vision, hearing, balance, or lower extremity strength impairment and those who used pain medication at least 5 days/week were more likely to be slow walkers at baseline and remain slow walkers at follow-up. In manuscript 3, group-based trajectory modeling was used to identify longitudinal trajectories of GS in older adults with DM, HTN or DM and HTN. Multinomial logistic regression was then conducted to examine the correlates of these trajectories. This study identified four GS trajectories in both cohorts: i) fast-stable GS, ii) intermediate GS with slow decline, iii) intermediate GS with moderate decline and iv) slow GS with fast decline. Additionally, one trajectory was unique to cohort A: intermediate-stable GS and two trajectories were unique to cohort B: fast GS with slow decline, and intermediate GS with fast decline. In both cohorts, individuals who were older, Black (non-Hispanic), had a higher number of chronic diseases or higher body mass index (BMI) were more likely to belong to a trajectory group with faster GS decline. Conversely, individuals with higher education, or higher baseline GS were less likely to belong to a trajectory group with faster GS decline. From a population health perspective, findings from this thesis can inform large-scale monitoring and management strategies to mitigate GS decline in older adults with DM, HTN or DM and HTN. For example, individuals who are older, identify as Black non-Hispanic or those with a higher number of chronic diseases or higher BMI may benefit from more frequent monitoring of their GS. Moreover, findings from this thesis can be used to determine how older adults with different multimorbidity patterns, or different types of sensory and motor impairments respond to interventions. Lastly, older adults with DM and/or HTN should be educated about the importance of maintaining their GS as they age to prevent adverse outcomes including falls, hospitalization, and premature death. / Thesis / Doctor of Philosophy (PhD) / Diabetes and hypertension are common chronic diseases among older adults globally. Moreover, these two chronic diseases are frequently found in the same individual due to shared risk factors including physical inactivity, and family history. Additionally, older adults with diabetes and/or hypertension are at risk of developing complications including vision loss, heart disease and stroke. These complications often cause impairments (i.e., changes in body structure or function) which also occur with aging including vision and hearing impairment, pain, and balance impairment which may reduce physical function (e.g., walking speed). There is a need for research to examine which other chronic diseases are linked to diabetes and hypertension and the impact of these diseases and disease-related impairments on walking speed among older adults with diabetes and/or hypertension. Moreover, it is important to examine how walking speed changes over time (i.e., trajectories) in older adults with diabetes and/or hypertension. Results from this thesis show that older adults with diabetes and/or hypertension who used pain medication at least 5 days/week, had vision, balance, or lower extremity strength impairment as well as older adults who are female, Black non-Hispanic, had a higher number of chronic diseases and a higher body mass index were at greatest risk of reduced walking speed. On the other hand, higher education and higher baseline walking speed were linked to lower risk of walking speed decline. Older adults who were identified as “high-risk” may benefit from closer monitoring and management of their walking speed to prevent further decline.

No / Background - Although there is a wealth of research into the kinematic coupling between the foot and shank, it remains unclear whether the relationship is stable across speed and mode of gait. The aim of this study was to determine whether the coupling relationship between the forefoot, rearfoot and shank differed between walking and running, and across different running speeds. Methods Twelve subjects walked/ran barefoot over-ground at one walking and three running speeds. The shank, rearfoot and forefoot were modelled as rigid segments and three-dimensional joint kinematics were determined using a seven camera ProReflex system. Coupling between the forefoot, rearfoot and shank was assessed using cross-correlation and vector coding techniques. Findings Cross-correlation of rearfoot eversion/inversion with shank internal/external rotation was lower in walking (r=0.49) compared to running (r>0.95). This was also the case between rearfoot frontal plane and forefoot sagittal plane motion (walking, r=¿0.80; running, r=¿0.96). Rearfoot frontal plane and forefoot transverse plane cross-correlation was high in both running and walking (r>0.90), but there was little evidence of any coupling between rearfoot frontal plane and forefoot frontal plane motion in any condition. No differences in cross-correlations were found between the three running speeds. Interpretation Kinematic coupling between the forefoot, rearfoot and shank was weak during walking relative to running. In particular, the low cross-correlation between rearfoot eversion/inversion and shank internal/external rotation during walking implies the two motions are not rigidly linked, as has been assumed in previous injury models.

<p>In community mobility, walking is commonly completed with other concurrent tasks, described as locomotor multitasks. Many locomotor multitasks rely on vision for both gait and concurrent tasks. When each of the individual tasks uses the same perceptual modality (e.g. vision), structural interference occurs. Structural interference is different from capacity interference, which refers to tasks competing for limited cognitive resources. While locomotor multitask studies have demonstrated that completing the locomotor multitask typically leads to performance impairment in gait and/or the concurrent task, the wide range of tasks has confounded the ability to fully understand how structural and capacity interference affect multitask performance. Thus, the purpose of this dissertation was to delineate how structural interference (Study 1) and capacity interference (Study 2) affect gait multitask performance. To facilitate comparison across studies, the two studies (Study 1 and Study 2) in this dissertation used the same gait task – obstacle crossing – and the same cognitive task – a visual discrete reaction time (RT) task. A discrete RT task was completed while approaching to an obstacle, where visual information regarding obstacle is being gathered to plan for the successful obstacle crossing. In Study 1, to determine if structural interference affects performance impairment in young and older adults, gaze diversion was manipulated by the RT task location (gaze diverted to the obstacle, and gaze diverted away from the obstacle). The RT task was also completed while standing to strengthen the interpretation that any performance impairments were due to structural interference. Study 1 results indicated that structural interference affects both gait and cognitive task performance. Structural interference demonstrated performance impairments in both young and older adults, but the strategies were different. Young adults were more likely adopt gait behavior that increased the risk of tripping when gaze was diverted away from the obstacle (high structural interference), but older adults demonstrated a strategy that decreased the risk of trip when gaze was diverted to the obstacle (low structural interference). This finding highlights the critical role of vision in adaptive gait. In study 2, to determine if capacity interference affects performance impairment in young adults, both gait and cognitive task were manipulated while structural interference was held constant; gait task was manipulated by obstacle height (level walking, 15% leg length height, and 30% leg length height obstacle), and cognitive tasks were three RT tasks (Simple RT, Choice RT, Simon RT). The baseline for each gait task (without RT task) and cognitive task (while seating) was also measured. Capacity interference demonstrated that task prioritization strategy was different for gait challenge versus cognitive challenge in young adults. As gait task difficulty increased, gait task was prioritized. Conversely, as cognitive task difficulty increased, cognitive task was prioritized. This finding highlights that young adults have the ability to flexibly allocate the resources to accomplish the multitask. Lastly, an interesting finding from two studies (Study 1 and Study 2) was when interference is applied during the planning phase – during the approach to the obstacle – structural interference has a greater effect on obstacle crossing performance than capacity interference.</p>

Age-related structural and molecular changes in older adults have been shown to significantly affect their cognitive and motor functions (Trollor and Valenzuela, 2001). Given the growing population of older adults, it is imperative to bridge the gaps in scientific understanding of cognition and motor capabilities in healthy older adults’ population. This study investigates five major neurochemicals and their potential correlations with gait, balance, executive function, and attention in healthy older adults. Additionally, we explore the interplay between cognition and motor performance in our participants. Furthermore, we hypothesize that the neurochemical values of interest may serve as predictive indicators for motor performance and cognition in healthy older adults.

No description available.

No description available.

No description available.