Cognitive-motor dual-task interference in adults with sickle cell disease.

BACKGROUND: Sickle cell disease (SCD) is a genetic disorder that causes physical and cognitive impairment due to hemolysis, painful vaso-occlusion episodes, joint avascular necrosis, and strokes. As individuals with SCD age and develop conditions impacting their physical and cognitive function, their ability to multitask successfully and safely may decline. Cognitive-motor dual-task interference occurs when there is deterioration in one or both tasks while dual-tasking relative to single-tasking. Dual-task assessment (DTA) is a valuable measure of physical and cognitive function; however, there is limited data on DTA in adults with SCD. RESEARCH QUESTION: Is DTA a feasible and safe method of measuring physical and cognitive function in adults with SCD? What patterns of cognitive-motor interference occur in adults with SCD? METHODS: We enrolled 40 adults with SCD (mean age 44 years, range 20-71) in a single-center prospective cohort study. We used usual gait speed as the measure of motor performance and verbal fluency (F, A, and S) as the measure of cognitive performance. We measured feasibility as the proportion of consented participants able to complete the DTA. We calculated the relative dual-task effect (DTE %) for each task and identified patterns of dual-task interference. RESULTS: Most consented participants completed the DTA (91%, 40/44) and there were no adverse events. There were 3 main dual-task interference patterns for the first trial using letter 'A': Motor Interference (53%, n = 21), Mutual Interference (23%, n = 9), and Cognitive-Priority Tradeoff (15%, n = 6). For the second trial using letter 'S', there were two main dual-task interference patterns: Cognitive-Priority Tradeoff (53%, n = 21) and Motor Interference (25%, n = 10). STATEMENT OF SIGNIFICANCE: DTA was feasible and safe in adults with SCD. We identified specific patterns of cognitive-motor interference. This study supports further evaluation of DTA as a potentially useful tool to measure physical and cognitive function in ambulatory adults with SCD.

Brief composite mobility index predicts post-stroke fallers after hospital discharge.

Introduction: Community-dwelling, ambulatory stroke survivors fall at very high rates in the first 3-6 months. Current inpatient clinical assessments for fall risk have inadequate predictive accuracy. We found that a pre-discharge obstacle-crossing test has excellent specificity (83%) but lacks acceptable sensitivity (67%) for identifying would-be fallers and non-fallers post discharge. Hypothesis: We assessed the hypothesis that combining the obstacle-crossing test with other highly discriminatory fall risk factors would compensate for the obstacle test's fair sensitivity and yield an instrument with superior prediction accuracy. Methods: 45 ambulatory stroke survivors (60 ± 11 years old, 15 ± 11 days post stroke) being discharged home completed a battery of physical performance-based and self-reported measures 1-5 days prior to discharge. After discharge, participants were prospectively followed and classified as fallers (≥1 fall) or non-fallers at 3 months. Pre-discharge measures with the largest effect sizes for differentiating fallers and non-fallers were combined into a composite index. Several variations of the composite index were examined to optimize accuracy. Results: A 4-item discharge composite index significantly predicted fall status at 3-months. The goodness of fit of the regression model was significantly better than the obstacle-crossing test alone, χ 2(1) = 6.036, p = 0.014. Furthermore, whereas the obstacle-crossing test had acceptable overall accuracy (AUC 0.78, 95% CI, 0.60-0.90), the composite index had excellent accuracy (AUC 0.85, 95% CI, 0.74-0.96). Combining the obstacle-crossing test with only the step test produced a model of equivalent accuracy (AUC 0.85, 95% CI, 0.73-0.96) and with better symmetry between sensitivity and specificity (0.71, 0.83) than the 4-item composite index (0.86, 0.67). This 2-item index was validated in an independent sample of n = 30 and with bootstrapping 1,000 samples from the pooled cohorts. The 4-item index was internally validated with bootstrapping 1,000 samples from the derivation cohort plus n = 9 additional participants. Conclusion: This study provides convincing proof-of-concept that strategic aggregation of performance-based and self-reported mobility measures, including a novel and demanding obstacle-crossing test, can predict post-discharge fallers with excellent accuracy. Further instrument development is warranted to construct a brief aggregate tool that will be pragmatic for inpatient use and improve identification of future post-stroke fallers before the first fall.

Utility of an obstacle-crossing test to classify future fallers and non-fallers at hospital discharge after stroke: A pilot study.

BACKGROUND: Existing clinical assessments of balance and functional mobility have poor predictive accuracy for prospectively identifying post-stroke fallers, which may be due to a lack of ecological complexity that is typical of community-based fall incidents. RESEARCH QUESTION: Does an obstacle-crossing test at hospital discharge predict fall status of ambulatory stroke survivors 3 months after discharge? METHODS: Ambulatory stroke survivors being discharged home completed an obstacle-crossing test at hospital discharge. Falls were tracked prospectively for 3 months after discharge. Logistic regression examined the relationship between obstacle-crossing at discharge (pass/fail) and fall status (faller/non-faller) at 3 months post discharge. RESULTS: 45 participants had discharge obstacle test and 3-month fall data. 21 (47 %) participants experienced at least one fall during follow-up, with 52 % of the falls occurring within the first month after discharge. Of the 21 fallers, 14 failed the obstacle-crossing test (67 % sensitivity). Among the 24 non-fallers, 20 passed the obstacle-crossing test (83 % specificity). The area under the receiver operating characteristic curve was 0.75 (95 % CI 0.60-0.90). Individuals who failed the obstacle-crossing test were 10.00 (95 % CI: 2.45-40.78) times more likely to fall in the first 3 months after discharge. The unadjusted logistic regression model correctly classified 76 % of the subjects. After adjusting for age, sex, days post stroke, and post-stroke disability, the odds ratio remained significant at 6.93 (95 % CI: 1.01-47.52) and correctly classified 79.5% of the participants. SIGNIFICANCE: The obstacle-crossing test may be a useful discharge assessment to identify ambulatory stroke survivors being discharged home who are likely to fall in the first 3 months post discharge. Modifications to improve the obstacle-crossing test sensitivity should be explored further.

Participant Outcomes of a Student-Run, Intensive, Short-Term, Task-Specific Rehabilitation Program for Individuals Post-Stroke.

Stroke survivors continue to face chronic disability and limited access to early, continuous, and long-term rehabilitation. This pilot study examined the impact of a 6-day, intensive, short-term, task-specific rehabilitation program (ISTRP) on outcomes post-stroke as part of a service-learning experience (SLE) for Doctor of Physical Therapy (DPT) students. Participants (n=19) post-stroke completed a 6-day, student-led ISTRP. Outcome measures were used to assess balance, functional gait, upper extremity motor impairment, and self-reported recovery. Significant differences from pre- to post-intervention were found for all outcome measures (p<0.05) except for the Stroke-Impact Scale-16. This pilot study addresses a gap in literature and suggests an ISTRP should be further explored while integrating other allied health disciplines.

Cognitive-motor dual-task gait training within 3 years after stroke: A randomized controlled trial.

BACKGROUND: Dual-task gait training may improve dual-task gait speed after stroke, but the effects on the relative amount of dual-task interference are unclear. OBJECTIVE: To compare the efficacy of dual-task gait training (DTGT) and single-task gait training (STGT) on cognitive-motor dual-task interference after stroke. METHODS: 36 adults within 3 years of stroke were randomized 1:1 to STGT or DTGT, 3 times a week for 4 weeks. The primary outcomes were the relative dual-task effect on gait speed (DTEg, %) and cognitive task performance (DTEc, %) during walking at preferred and fast speed in two different dual-task conditions (auditory Stroop, auditory clock task). RESULTS: There were no treatment effects on DTEg or DTEc in either group for either dual-task at either walking speed. Across all participants, there were significant improvements in both single and dual-task gait speed in all conditions, without any relative change in the dual-task effect. Subgroup analysis suggested that those with greater interference at baseline may benefit more from DTGT. CONCLUSIONS: DTGT and STGT improved single and dual-task gait speed but did not change the amount of relative interference. The findings may be confounded by an unexpectedly small amount of gait-related dual-task interference at baseline.

Patterns of cognitive-motor dual-task interference post stroke: an observational inpatient study at hospital discharge.

BACKGROUND: Many ambulatory stroke survivors are discharged to community settings where they will confront highly attention-demanding mobility situations. Very little is known about cognitive-motor interference during walking in acutely rehabilitating stroke survivors. AIM: To examine the magnitude and patterns of cognitive-motor dual-task interference at hospital discharge post stroke and explore the characteristics associated with distinct interference patterns. DESIGN: Observational study. SETTING: Acute care and inpatient rehabilitation centers. POPULATION: Forty-seven adults with hospital admission for stroke who were being discharged to home. Mean age was 59.5 years (SD=11.7) and median days post stroke was 14 (IQR=7-21). METHODS: Gait and cognitive (category naming task) performance were assessed under single- and dual-task conditions at hospital discharge. Dependent variables were gait speed, stride duration, stride duration variability, stride length, cadence, and correct response rate. Single and dual-task values were compared to assess the effects of dual-tasking on gait and category naming. Relative dual-task effects on gait speed and cognitive performance were plotted to identify patterns of dual-task interference. Exploratory analysis compared clinical characteristics between subgroups defined by pattern of interference. RESULTS: There were significant dual-task declines in gait speed, with corresponding dual-task effects on stride length, cadence, and stride duration, but no dual-task effects on stride duration variability or correct response rate. Dual-task effects on the category naming task were not significant due to large between-subject variability. Three predominant patterns of cognitive-motor interference were evident: mutual interference (37% of participants), gait interference (30% of participants), and cognitive-priority trade-off (22% of participants) - these patterns reflect the consistently observed negative dual-task effect on gait speed with positive, negative, or null effects on category naming. Participants who demonstrated cognitive-priority trade-off pattern of interference had significantly worse single-task category-naming performance, while those with mutual interference had greater overall stroke severity. CONCLUSIONS: Cognitive-motor dual-task interference on gait speed is highly prevalent in ambulatory stroke survivors with mild cognitive-linguistic impairments at hospital discharge. Variability in cognitive-task performance under dual-task conditions has implications for the reliability of dual-task assessment after stroke. CLINICAL REHABILITATION IMPACT: Assessment of dual-task walking is feasible as a predischarge evaluation of attention-demanding mobility function after stroke.

Relationships between gait variability and ambulatory activity post stroke.

BACKGROUND: Fall risk and balance confidence are related to gait variability and ambulatory activity post stroke, yet whether a relationship exists between gait variability and ambulatory activity is unknown. Knowing if gait variability measured under naturalistic conditions is related to ambulatory activity could explain more about the relationship between falls and walking activity post-stroke. OBJECTIVES: To examine relationships between spontaneous, daily ambulatory activity and gait variability during single- and dual-task walking, in low- and high-distraction settings in adults post stroke. METHODS: Sixteen community-dwelling adults post stroke participated in a cross-sectional study. Spatiotemporal gait parameters were recorded during single- and cognitive-motor dual-task walking in low- and high-distraction settings. Coefficient of variation was calculated for stride length and stride duration. Average walking bout duration, maximum walking bout duration, and total number of steps per day were captured using an activity monitor. Correlations between ambulatory activity measures and gait variability were examined. RESULTS: In the high-distraction setting, single-task stride duration variability was negatively related to all three ambulatory activity measures, but the strongest relationship was a negative correlation between dual-task stride duration variability and average walking duration. In the low-distraction setting, single-task stride duration variability was negatively related to maximum walking duration. None of the other variability measures were related to ambulatory activity. CONCLUSIONS: The finding that stride duration variability in a high-distraction environment, with or without an additional cognitive task, is related to ambulatory activity in community-dwelling stroke survivors suggests that assessments incorporating attentional demands of real-world walking may be useful additions to clinical practice.

Visual scanning behavior during distracted walking in healthy young adults.

BACKGROUND: An epidemic of pedestrian accidents when walking while texting suggests that people are less aware of their surroundings during distracted walking, and highlights the importance of visual scanning for pedestrian safety. Quantitative examination of visual scanning during distracted walking is still lacking. RESEARCH QUESTION: Is visual scanning behavior altered by distracted walking in healthy young adults? METHODS: We compared visual scanning behavior in 20 young adults during usual (single-task) walking, walking while performing a letter-fluency task, and walking while texting. Visual scanning behavior was measured by fixation count and dwell time percentage in specific areas of interest. Dual-task effects on gait speed, letter fluency, texting speed and accuracy, and situational awareness were also examined. RESULT: Visual scanning behavior differed between the three walking conditions. During dual-task letter fluency, participants had significantly more non-walking path fixations than either of the other two conditions (i.e., more frequent, broader visual scanning). Conversely, during dual-task texting, gaze was focused predominantly on the phone, with little visual scanning of the walking path and surrounding environment. When walking without texting or talking, gaze was directed equally to far walking path and surrounding environment. SIGNIFICANCE: Texting while walking is associated with a considerable reduction in overt visual attention to the walking path and surrounding areas. Whether this translates to reduced conscious awareness of environmental stimuli remains unclear. Performing a verbal task while walking was associated with more frequent, wider visual scanning behavior, which may be specific to the nature of the verbal task in this study.

Dual-Task Gait and Alzheimer's Disease Genetic Risk in Cognitively Normal Adults: A Pilot Study.

BACKGROUND: Dual-task paradigms, in which an individual performs tasks separately and then concurrently, often demonstrate that people with neurodegenerative disorders experience more dual-task interference, defined as worse performance in the dual-task condition compared to the single-task condition. OBJECTIVE: To examine how gait-cognition dual-task performance differs between cognitively normal older adults with and without an APOE ɛ4 allele. METHODS: Twenty-nine individuals ages 60 to 72 with normal cognition completed a dual-task protocol in which walking and cognitive tasks (executive function, memory) were performed separately and concurrently. Fourteen participants carried APOE ɛ4 alleles (ɛ3/ɛ4 or ɛ2/ɛ4); fifteen had APOE genotypes (ɛ2/ɛ2, ɛ2/ɛ3, or ɛ3/ɛ3) associated with lower risk of Alzheimer's disease (AD). RESULTS: The two risk groups did not differ by age, sex, race, education, or gait or cognitive measures under single-task conditions. Compared to low risk participants, APOE ɛ4 carriers tended to exhibit greater dual-task interference. Both the memory and executive function tasks resulted in dual-task interference on gait, but effect sizes for a group difference were larger when the cognitive task was executive function. In the dual-task protocol that combined walking and the executive function task, effect sizes for group difference in gait interference were larger (0.62- 0.70) than for cognitive interference (0.45- 0.47). DISCUSSION: Dual-task paradigms may reveal subtle changes in brain function in asymptomatic individuals at heightened risk of AD.

Relationship Between Dual-Task Gait Speed and Walking Activity Poststroke.

BACKGROUND AND PURPOSE: Gait speed does not adequately predict whether stroke survivors will be active in the community. This may be because traditional single-task gait speed does not sufficiently reproduce the demands of walking in the real world. This study assessed whether dual-task gait speed accounts for variance in daily ambulatory activity above what can be predicted with habitual (single task) gait speed in community-dwelling stroke survivors. METHODS: Twenty-eight community-dwelling individuals, 58.2 years of age (SD=16.6), 8.9 months poststroke (interquartile range, 3.7-19.4), completed a gait and cognitive task in single- and dual-task conditions. Daily ambulatory activity was captured using a physical activity monitor. A regression analysis examined R2 changes with single- and dual-task gait speed. RESULTS: Single-task gait speed explained 15.3% of the variance in daily ambulatory activity (P=0.04). Adding dual-task gait speed to the regression model increased the variance explained by an additional 20.6% (P=0.04). CONCLUSIONS: Gait speed assessed under attention-demanding conditions may improve explanation of variance in daily ambulatory activity after stroke.

Aging effects on leg joint variability during walking with balance perturbations.

BACKGROUND: Older adults are more susceptible to balance perturbations during walking than young adults. However, we lack an individual joint-level understanding of how aging affects the neuromechanical strategies used to accommodate balance perturbations. RESEARCH QUESTION: We investigated gait phase-dependence in and aging effects on leg joint kinematic variability during walking with balance perturbations. We hypothesized that leg joint variability would: 1) vary across the gait cycle and 2) increase with balance perturbations. We also hypothesized that perturbation effects on leg joint kinematic variability would be larger and more pervasive in older versus young adults. METHODS: We collected leg joint kinematics in young and older adults walking with and without mediolateral optical flow perturbations of different amplitudes. RESULTS: We first found that leg joint variability during walking is gait phase-dependent, with step-to-step adjustments occurring predominantly during push-off and early swing. Second, young adults accommodated perturbations almost exclusively by increasing coronal plane hip joint variability, likely to adjust step width. Third, perturbations elicited larger and more pervasive increases in all joint kinematic outcome measures in older adults. Finally, we also provide insight into which joints contribute more to foot placement variability in walking, adding that variability in sagittal plane knee and coronal plane hip joint angles contributed most to that in step length and step width, respectively. SIGNIFICANCE: Taken together, our findings may be highly relevant to identifying specific joint-level therapeutic targets to mitigate balance impairment in our aging population.