Age-related changes in gait adaptability in response to unpredictable obstacles and stepping targets

Are age-related changes in perceptual-motor regulation related to an increased falls risk?

Purpose/Hypothesis: Age-related balance deficits and falls pose serious health risks for older adults. Older adults fall most often during dynamic activities such as gait, especially when surfaces are irregular or varied. Gait requires dynamic balance, the ability to maintain balance while moving, and is controlled by integration of multiple sensory and motor systems. Success with dynamic balance depends in part on an individual's ability to adapt to changing sensory environments. Knowledge is limited concerning the adaptations to movement strategies must occur for older and younger adults to maintain dynamic balance during challenges to two key sensory systems, proprioception and vision. The purpose of this study was to characterize the adaptive balance strategies older and younger adults produced during gait under conditions of single sensory challenge (proprioceptive or visual) and simultaneous proprioceptive and visual challenge. Subjects: In this 2(group) X 4(condition) factorial design study, 40 subjects (20 young/20 older adults) ambulated under 4 conditions: a level firm surface, unstable surface, firm surface with vision obscured, and unstable surface with vision obscured. Materials/Methods: Adaptation to gait was measured by changes in gait speed, stride length, cadence, and Gait Stability Ratio (GSR). Adaptation regarding head stability was measured by peak head and trunk angular velocities in three planes of motion: pitch, roll and yaw. Results: Significant main effects for gait condition were found for gait speed (p<.0001) and cadence (p<.0001). Significant main effects for the interaction of age and gait condition were found for stride length (p = .001) and GSR (p = .002). A significant main effect for condition was found for peak trunk velocity in the roll plane (p<.0001). Significant interaction effects were found for peak head velocity in pitch (p = .001), roll (p = .006) and yaw (p = .003) and for peak trunk velocity in pitch (p = .008) and yaw (p<.0001). Conclusions: Both older and younger adults adapt gait speed, cadence and lateral trunk motion under conditions that challenge sensory systems in order to assume a more stable gait. Adaptations to stride length, GSR, and peak head and trunk velocities in other planes, however, differ for older and younger adults depending on the type of sensory challenge. Older and younger adults exhibit adaptive changes to gait and head stability parameters that vary in degree as challenge increases. Under the same conditions, older adults in general show greater adaptation to gait and achieve less stability of the head in space than do young adults indicating poorer control of dynamic balance. Clinical Relevance: The results of this study add to the understanding of dynamic balance control and age-related changes in balance. This knowledge has relevance clinically in that it may improve identification of older adults with an increased risk for falling.

Stride-to-stride fluctuations during walking reflect age-related changes in gait adaptability and are estimated with nonlinear measures that confine data collection to controlled settings. Smartphones, with their embedded accelerometers, may provide accessible gait analysis throughout the day. This study investigated age-related differences in linear and nonlinear gait measures estimated from a smartphone accelerometer (SPAcc) in an unconstrained, free-living environment. Thirteen young adults (YA) and 11 older adults (OA) walked within a shopping mall with a SPAcc placed in their front right pants pocket. The inter-stride interval, calculated as the time difference between ipsilateral heel contacts, was used for dependent measures calculations. One-way repeated-measures analysis of variance revealed significant (p < 0.05) age-related differences (mean: YA, OA) for stride-time standard deviation (0.04 s, 0.05 s) and coefficient of variation (3.47%, 4.16%), sample entropy (SaEn) scale 1 (1.70, 1.86) and scale 3 (2.12, 1.80), and statistical persistence decay (31 strides, 23 strides). The fractal scaling index was not different between groups (0.93, 0.95), but exceeded those typically found in controlled settings, suggesting an upregulation in adaptive behaviour likely to accommodate the increased challenge of free-living walking. These findings support the SPAcc as a viable telehealth instrument for remote monitoring of gait dynamics, with implications for unsupervised fall-risk assessment.

BackgroundGait speed is a strong predictor of a wide range of adverse health outcomes in older adults. Mean values for gait speed in community-dwelling older adults vary substantially depending on population characteristics, suggesting that social, biological, or health factors might explain why certain groups tend to self-select their gait speed in different patterns. The vast majority of studies reported in the literature present data from North American and European populations. There are few population-based studies from other regions with a different ethnicity and/or social and health conditions. To address this, the present study identified the mean usual and fast gait speeds in a representative multiracial population of community-dwelling older adults living in a developing country, and explored their association with sociodemographic, mental and physical health characteristics.MethodsThis was a cross-sectional population-based study of a sample of 137 men and 248 women, aged 65 years and over. Usual gait speed and fast gait speed were measured on a 4.6 m path. Participants were classified into slow, intermediate, and faster groups by cluster analysis. Logistic regression analysis was used to estimate the independent effect of each factor on the odds of presenting with a slower usual and slower fast gait speeds.ResultsParticipants had a mean (SD) usual gait speed of 1.11 (0.27) m/s and a mean fast gait speed of 1.39 (0.34) m/s. We did not observe an independent association between gait speed and race/ethnicity, educational level, or income. The main contributors to present a slower usual gait speed were low physical activity level, stroke, diabetes, urinary incontinence, high concern about falling, and old age. A slower fast gait speed was associated with old age, low physical activity, urinary incontinence and high concern about falling.ConclusionA multiracial population of older adults living in a developing country showed a similar mean gait speed to that observed in previously studied populations. The results suggest that low physical activity, urinary incontinence and high concern about falling should not be neglected and may help identify those who might benefit from early intervention.

BackgroundSarcopenia‐related parameters may have differential impacts on health‐related outcomes in older adults. We examined dose–response relationships of body composition, muscle strength, and physical performance with incident disability and mortality.MethodsThis prospective study included 1765 Japanese residents (862 men; 903 women) aged ≥65 years who participated in health check‐ups. Outcomes were incident disability and all‐cause mortality. Fat mass index (FMI) and skeletal muscle mass index (SMI), determined using segmental multi‐frequency bioelectrical impedance analysis, handgrip strength (HGS), and usual gait speed (UGS) were measured. We determined multivariate‐adjusted hazard ratios (HRs) for disability and mortality relative to sex‐specific reference values (FMI: medians; SMI: 7.0 kg/m2 for men and 5.7 kg/m2 for women; HGS: 28 kg for men and 18 kg for women; or UGS: 1.0 m/s for both sexes). Association shapes were examined using restricted cubic splines or fractional polynomial functions.ResultsThe median follow‐up was 5.3 years; 107 (12.7%) men and 123 (14.2%) women developed disability, and 101 (11.7%) men and 56 (6.2%) women died. FMI did not impact any outcome in men and disability in women, while an FMI ≤ 7.3 kg/m2 (median) was significantly associated with higher mortality risk in women, compared with median FMI. SMI did not impact disability in either sex and mortality in women, but showed a significant inverse dose–response relationship with mortality risk in men [HRs (95% confidence intervals) of minimum and maximum values compared with the reference value: 2.18 (1.07–4.46) and 0.43 (0.20–0.93), respectively], independent of HGS and UGS. HGS and UGS showed a significant inverse dose–response relationship with disability in both sexes [HGS: 1.71 (1.00–2.91) and 0.31 (0.09–0.99), respectively, in men, 2.42 (1.18–4.96) and 0.41 (0.20–0.85), respectively, in women; UGS: 2.14 (1.23–3.74) and 0.23 (0.08–0.67), respectively, in men, 3.26 (2.07–5.14) and 0.11 (0.05–0.26), respectively, in women] and mortality in women [HGS: 6.84 (2.84–16.47) and 0.06 (0.02–0.21), respectively; UGS: 2.67 (1.14–6.27) and 0.30 (0.11–0.85), respectively], independent of body composition, but did not impact mortality in men.ConclusionsDisability risk was more dependent on muscle strength and physical performance in both sexes. Mortality risk in men was more dependent on muscle mass, and mortality risk in women was influenced by lower fat mass along with muscle strength and physical performance. Although improving muscle strength and physical performance should be the first target for health promotion, it is also necessary to pay attention to body composition to extend life expectancy in older adults.

Synergies in the ground reaction forces and moments during double support in curb negotiation in young and older adults

OBJECTIVEDiabetic peripheral neuropathy (DPN) alters walking. Yet, the compensatory role of central locomotor circuits remains unclear. We hypothesized that walking outcomes would be more closely related to regional gray matter volumes in older adults with DPN as compared with nonneuropathic diabetic patients and nondiabetic control subjects.RESEARCH DESIGN AND METHODSClinically important outcomes of walking (i.e., speed, stride duration variability, and double support time) were measured in 29 patients with DPN (type 2 diabetes with foot-sole somatosensory impairment), 68 diabetic (DM) patients (type 2 diabetes with intact foot-sole sensation), and 89 control subjects. Global and regional gray matter volumes were calculated from 3 Tesla magnetic resonance imaging.RESULTSDPN subjects walked more slowly (P = 0.005) with greater stride duration variability (P < 0.001) and longer double support (P < 0.001) as compared with DM and control subjects. Diabetes was associated with less cerebellar gray matter volume (P < 0.001), but global gray matter volume was similar between groups. DPN subjects with lower gray matter volume globally (P < 0.004) and regionally (i.e., cerebellum, right-hemisphere dorsolateral prefrontal cortex, basal ganglia, P < 0.005) walked more slowly with greater stride duration variability and/or longer double support. Each relationship was stronger in DPN than DM subjects. In control subjects, brain volumes did not relate to walking patterns.CONCLUSIONSStrong relationships between brain volumes and walking outcomes were observed in the DPN group and to a lesser extent the DM group, but not in control subjects. Individuals with DPN may be more dependent upon supraspinal elements of the motor control system to regulate several walking outcomes linked to poor health in elderly adults.

Despite well-documented declines in most cognitive domains, some emotional processes appear to be preserved or even enhanced in late adulthood. A good example of this is the information processing bias older adults show towards positive relative to negative emotional stimuli, often referred to as the age-related positivity effect. The present thesis presents a series of experiments that were designed to better understand the mechanisms that contribute to age-related changes in emotional processing, focusing in particular on the role of cognitive mechanisms and neural networks. In Study 1 aimed to identify the underlying cognitive mechanisms of the positivity effect. The primary focus of this study was to explore the role of distractors during the early attention allocation stage, and to also measure how selective attentional processes during encoding influence later memory outcomes for emotional items. The results showed that consistent with prior literature, a memory positivity effect was found among older relative to younger adults. However, of particular interest was the finding that, participants’ memory for negative targets was not influenced by the presence of positive distractors. This finding suggests that positive distractors did not automatically capture older adults’ attention during encoding for negative items. Importantly, we found that participants’ pupillary responses to negative items mediated the relationship between age and the memory positivity effect, indicating that older adults use their cognitive control resources when encoding negative information, perhaps to down regulate the impact of negative emotions on their memory. Collectively, these two findings provide converging support for the cognitive control account of the positivity effect. Study 2 used a similar paradigm to Study 1 to examine the underlying neural networks involved in processing emotional items during working memory encoding among older and younger adults. Results indicated that a cognitive control network that included fronto-parietal regions, was functionally connected to the left ventrolateral prefrontal cortex during the encoding of negative items among older adults. This network contributed to performance, both accuracy and response times, in older adults’ group. A less distributed network was found for encoding of positive items among older and both items among younger adults. Although older adults recruited a same network that was functionally connected to the amygdala for encoding positive and negative items, younger adults recruited this particular network specifically for encoding negative items. This network facilitated older adults’ higher accuracy and faster response times during retrieval. Taken together, the results from these functional connectivity analyses suggest that there is differential engagement of brain networks connected to these two regions, which are modulated by the emotional valence. While two separate brain networks underlying the encoding of emotionally valence targets are connected to the vlPFC region, one distinct network is functionally connected to the amygdala and subserves the processing of both positive and negative targets. In Study 3 age-related differences in neural substrates involved when processing happy and angry expressions presented with direct versus averted gaze were investigated. This research was motivated by studies that show older adults not only have difficulties processing emotional cues such as facial expression and eye gaze cues, but also have problems integrating these cues. Study 3 provides the first empirical examination of the underlying neural correlates of age-related difficulties in integrating communicative cues. The results showed that for angry facial expressions, younger adults recruited distinct networks while processing direct versus averted eye-gaze cues, however, older adults showed a lack of neural sensitivity to these cues, recruiting a single network for both types of stimuli. In contrast, for happy facial expressions, only older adults showed neural sensitivity to eye gaze cues. Participants’ performance on the scanner task was then correlated with a measure of theory of mind (TOM). Younger (but not older) adults’ performance on a measure of TOM and recognition of angry expressions was differentially correlated with activation in two sets of brain regions as a function of eye gaze. Unlike younger adults, older adults’ performance on TOM was also differentially correlated with the key node of mentalizing brain network during happy expressions as a function of eye gaze. The findings from Study 3 suggest that the age-related difficulties in integrating facial cues could be associated with the recruitment of the mentalizing network when the task imposes high demand on social-cognitive processing. Taken together, the three Studies reported in this thesis provide novel insights into our understanding of age-related differences in the processing of emotionally valenced items, particularly with respect to initial encoding of this information, and how this relates to later memory outcomes. Moreover, for the first time the neural correlates of integrating two important types of facial cue has been identified, and potentially linked to broader social cognitive difficulties. Overall, the findings of this thesis have broad implications for understanding the underlying cognitive mechanisms and neural networks that contribute to age-related differences in the processing of emotional stimuli.

To describe age- and sex-related differences in gait patterns of community-living men and women using 3-D gait analysis. Subjects (n=2006) aged 40-84 years participated in the National Institute for Longevity Sciences-Longitudinal Study of Aging (NILS-LSA). Spatiotemporal components, including velocity, step length, step frequency, and double support time during a gait cycle, were calculated from 3-D coordinates and vertical force data. Velocity, step length and step frequency were normalized by leg length and acceleration due to gravity, and double support time was normalized to gait cycle duration. Spatiotemporal walking variables of brisk velocity and step length were significantly greater in men than in women, while comfortable velocity and comfortable and brisk step frequencies and double support times were greater in women than in men. Age-related changes were marked at 70-84 years in most spatiotemporal variables in both sexes during comfortable walking. During brisk walking, age-related changes were observed from a younger age than during comfortable walking, and there were sex-related differences. The age-related gait alteration was obvious among those aged 70 years and older, and it accelerated markedly in women's brisk walking intensity.

Effects of walking surfaces and footwear on temporo-spatial gait parameters in young and older people

Normal and limited vision gait was investigated in individuals with Parkinson disease (PD), healthy older and healthy young individuals. Participants walked a GAITRite mat with normal vision or vision of lower limbs occluded. Results indicate individuals with PD walked more slowly, with shorter and wider steps, and spent more time in double support with limited vision as compared to full vision. Healthy young and old individuals took shorter steps but were otherwise unchanged between conditions.

This study was designed to extend research on motor skill development in autism spectrum disorder using a dual-task skill. Nine autistic and 18 non-autistic youths walked without grasping or while reaching to grasp a small or large object. Step extremity ratio, percent time in double support, and normalized speed were quantified. We hypothesized that gait would differ between autistic and non-autistic youth and that differences would be moderated by the phase (approach and grasp) and the complexity of the task (walking and grasping versus walking alone). Although gait parameters were similar during the walking-only trials, the combined task resulted in slower speed and shorter steps in autistic youth, particularly during the grasp phase. These findings, while in a small sample, offer preliminary evidence that autistic youth who show typical gait during simple assessments of motor ability may have difficulties in more complex tasks that require the coordination of movements.

Since the initial scientific statement on Secondary Prevention of Coronary Heart Disease (CHD) in the Elderly was published in 2002,1 several trends have continued that make an update highly appropriate. First, the graying of the US population and those of other industrialized countries has progressed unabated because more adults are surviving into their senior years. The number of Americans aged ≥75 years was estimated at 18.6 million in 2010, representing ≈6% of the population,2 and it is expected to double by 2050. The population aged ≥85 years is growing the most rapidly, with numbers expected to reach 19.5 million by 2040. In 2008, 67% of the 811 940 cardiovascular deaths in the United States occurred in people aged ≥75 years.3 In parallel to this increase in the older adult demographic, the number of Americans with CHD has increased to an estimated 16.3 million, more than half of whom are >65 years of age.3 Similarly, 7 million have had a stroke, the incidence of which approximately doubles with successive age decades after 45 to 54 years.3 Peripheral artery disease (PAD) affects 8 to 10 million Americans, the majority of whom are >65 years of age. Between 2015 and 2030, annual US costs related to atherosclerotic cardiovascular disease (ASCVD) are projected to increase from $84.8 billion to $202 billion.3 Moreover, given that ASCVD often undermines functional capacity and independence and increases reliance on long-term care, indirect expenses related to ASCVD are also expected to increase. Thus, the need for effective secondary prevention measures in the older adult population with known ASCVD has never been greater. Notably, the 2011 American Heart Association (AHA)/American College of Cardiology Foundation (ACCF) updated guidelines for secondary prevention of CHD broadened …

Falls are the leading cause of unintentional deaths in older adults, with nearly one-third of adults older than 65 years falling annually. Previous work reveals that both medication status and gait changes are contributing factors to falls in older adults; however, it is unknown how these factors interact. Thus, the purpose of this investigation was to examine differences between gait biomechanics as a function of medication status in individuals older than 60 years with a self-reported history of falling. It was hypothesized that differences in gait mechanics would be observed as a function of the number of medications in these individuals. A total of 384 participants, age, mean (SD) = 73.2 (4.2) years; height, mean (SD) = 173.09 (16.4) cm; mass, mean (SD) = 65.45 (5.78) kg, were recruited from across the Southwest United States (Texas, New Mexico, Arizona, Nevada, and California) by the Electronic Caregiver Mobile Fall Risk Assessment Laboratory. Data for cadence, gait velocity, stride length, swing time, and double-support time were collected using a Walkway gait analysis system. Factor analysis was employed to determine whether the gait characteristics were similar to those observed in previous studies. A multivariate analysis with a follow-up univariate analysis was employed to determine group differences in gait factors and variables according to medication number (≥4 medications, n = 262 vs ≤3 medications, n = 122). Results of the factor analysis reveal that the data analyzed in the current study are similar to those observed in previous studies, with cadence (factor loading coefficient [FLC] = 0.745), gait velocity (FLC = 0.922), stride length (FLC = 0.789 for left and 0.790 for right) loading positively on a "pace" factor, swing time (FLC = 0.728 for right and 0.683 for left), and double-support time (FLC= 0.723) loading positively on a "rhythm" factor. The results of the multivariate analysis of variance revealed differences in gait factors across groups according to medication status. Univariate follow-up tests reveal that double-support time is longer and stride length is shorter in persons taking 4 or more medications as compared with those on 3 or fewer medications. The findings of this study indicate that certain abnormal gait parameters in participants with a history of falls are associated with taking 4 or more medications. Future studies should examine the extent to which gait changes and medications interact to predict falls.

Mesocorticolimbic dopaminergic innervation modulates Levodopa-related improvements in gait in older slow walking Adults: A [11C]PE2I PET study