Stride-to-stride variability while backward counting among healthy young adults

BACKGROUND: Little information exists about the involvement of attention in the control of gait rhythmicity. Variability of both stride time and stride length is closely related to the control of the rhythmic stepping mechanism. We sought 1) to determine whether backward counting while walking could provoke significant gait changes in mean values and coefficients of variation of stride velocity, stride time and stride length among healthy young adults; and 2) to establish whether change in stride-to-stride variability could be related to dual-task related stride velocity change, attention, or both. METHODS: Mean values and coefficients of variation of stride velocity, stride time and stride length were recorded using the Physilog(®)-system, at a self-selected walking speed in 49 healthy young adults (mean age 24.1 ± 2.8 years, women 49%) while walking alone and walking with simultaneous backward counting. Performance on backward counting was evaluated by recording the number of figures counted while sitting alone and while walking. RESULTS: Compared with walking alone, a significant dual-task-related decrease was found for the mean values of stride velocity (p < 0.001), along with a small but significant increase for the mean values and coefficients of variation of stride time (p < 0.001 and p = 0.015, respectively). Stride length parameters did not change significantly between both walking conditions. Dual-task-related increase of coefficient of variation of stride time was explained by changing stride velocity and variability between subjects but not by backward counting. The number of figures counted while walking decreased significantly compared to backward counting alone. Further, the dual-task related decrease of the number of enumerated figures was significantly higher than the dual-task related decrease of stride velocity (p = 0.013). CONCLUSION: The observed performance-changes in gait and backward counting while dual tasking confirm that certain aspects of walking are attention-demanding in young adults. In the tested group of 49 young volunteers, dual tasking caused a small decrease in stride velocity and a slight increase in the stride-to-stride variability of stride time, while stride velocity variability was not affected by the attention-demanding task. The increase in stride time variability was apparently the result of a change in gait speed, but not a result of dual tasking. This suggests that young adults require minimal attention for the control of the rhythmic stepping mechanism while walking

Satisfaction du franchisé : l'impact de la relation entre le franchisé et son franchiseur.

Relation franchiseur-franchisé; Franchise;

Relationship between dual-task related gait changes and intrinsic risk factors for falls among transitional frail older adults

Background and aims: Gait changes in dual-task conditions have been associated with an increased risk of falling in older adults, and become more important in increasingly frail older adults. We studied the relationship between commonly known intrinsic risk factors for falls and dual-task related gait changes among transitional frail older adults. Methods: Walking time and number of steps were measured while walking alone and while walking with counting backward on a 10-m walkway in 66 transitional frail older adults (mean age 83.6±6.1, 84.9% women). Uni- and multiple linear regression analyses were performed to explore the relationship between dual-task related gait changes (walking time and number of steps) and age over 85 years, polymedication, psychoactive drugs, poor distance vision, abnormal mobility and cognitive impairment. Results: Compared with walking alone, both walking time and number of steps increased significantly while counting backward (p<0.001). Polymedication and abnormal mobility were associated with a significant increase of walking time and number of steps (p<0.01 for unadjusted change, p<0.05 for adjusted change). Conclusions: Dual-task related gait changes were closely correlated with polymedication and impaired mobility in our sample of transitional frail older adults. These findings give some insight into the complexity of performing attention-demanding tasks while walking and accentuate the need for multi-factorial, personalized intervention strategies, to prevent decline in dual-task performance in this fall-prone populatio

Gait analysis in demented subjects: Interests and perspectives

Gait disorders are more prevalent in dementia than in normal aging and are related to the severity of cognitive decline. Dementia-related gait changes (DRGC) mainly include decrease in walking speed provoked by a decrease in stride length and an increase in support phase. More recently, dual-task related changes in gait were found in Alzheimer’s disease (AD) and non-Alzheimer dementia, even at an early stage. An increase in stride-to-stride variability while usual walking and dual-tasking has been shown to be more specific and sensitive than any change in mean value in subjects with dementia. Those data show that DRGC are not only associated to motor disorders but also to problem with central processing of information and highlight that dysfunction of temporal and frontal lobe may in part explain gait impairment among demented subjects. Gait assessment, and more particularly dual-task analysis, is therefore crucial in early diagnosis of dementia and/or related syndromes in the elderly. Moreover, dual-task disturbances could be a specific marker of falling at a pre-dementia stage

‘Faster counting while walking' as a predictor of falls in older adults

Objective: to establish whether changes in a spoken verbal task performance while walking compared with being at rest could predict falls among older adults. Design: prospective cohort study of 12 months' duration. Setting: twenty-seven senior housing facilities. Participants: sample of 187 subjects aged 75-100 (mean age 84.8±5.2). During enrollment, participants were asked to count aloud backward from 50, both at rest and while walking and were divided into two groups according to their counting performance. Information on incident falls during the follow-up year was monthly collected. Measurements: the number of enumerated figures while sitting on a chair and while walking, and the first fall that occurred during the follow up year. Results: the number of enumerated figures under dual-task as compared to single task increased among 31.5% of the tested subjects (n=59) and was associated with lower scores in MMSE (P=0.034), and higher scores in Geriatric Depression Scale (P=0.007) and Timed Up & Go (P=0.005). During the 12 months follow-up, 54 subjects (28.9%) fell. After adjusting for these variables, the increase in counting performance was significantly associated with falls (adjusted OR = 53.3, P < 0.0001). Kaplan-Meier distributions of falls differed significantly between subjects who either increased or decreased their counting performance (P < 0.0001). Conclusions: faster counting while walking was strongly associated with falls, suggesting that better performance in an additional verbal counting task while walking might represent a new way to predict falls among older adult

Symptom-based stratification of patients with primary Sjögren's syndrome: multi-dimensional characterisation of international observational cohorts and reanalyses of randomised clinical trials

Background Heterogeneity is a major obstacle to developing effective treatments for patients with primary Sjögren's syndrome. We aimed to develop a robust method for stratification, exploiting heterogeneity in patient-reported symptoms, and to relate these differences to pathobiology and therapeutic response. Methods We did hierarchical cluster analysis using five common symptoms associated with primary Sjögren's syndrome (pain, fatigue, dryness, anxiety, and depression), followed by multinomial logistic regression to identify subgroups in the UK Primary Sjögren's Syndrome Registry (UKPSSR). We assessed clinical and biological differences between these subgroups, including transcriptional differences in peripheral blood. Patients from two independent validation cohorts in Norway and France were used to confirm patient stratification. Data from two phase 3 clinical trials were similarly stratified to assess the differences between subgroups in treatment response to hydroxychloroquine and rituximab. Findings In the UKPSSR cohort (n=608), we identified four subgroups: Low symptom burden (LSB), high symptom burden (HSB), dryness dominant with fatigue (DDF), and pain dominant with fatigue (PDF). Significant differences in peripheral blood lymphocyte counts, anti-SSA and anti-SSB antibody positivity, as well as serum IgG, κ-free light chain, β2-microglobulin, and CXCL13 concentrations were observed between these subgroups, along with differentially expressed transcriptomic modules in peripheral blood. Similar findings were observed in the independent validation cohorts (n=396). Reanalysis of trial data stratifying patients into these subgroups suggested a treatment effect with hydroxychloroquine in the HSB subgroup and with rituximab in the DDF subgroup compared with placebo. Interpretation Stratification on the basis of patient-reported symptoms of patients with primary Sjögren's syndrome revealed distinct pathobiological endotypes with distinct responses to immunomodulatory treatments. Our data have important implications for clinical management, trial design, and therapeutic development. Similar stratification approaches might be useful for patients with other chronic immune-mediated diseases. Funding UK Medical Research Council, British Sjogren's Syndrome Association, French Ministry of Health, Arthritis Research UK, Foundation for Research in Rheumatology

How France's potential franchisees reach their decisions. A comparison with franchiseers' perceptions

This article discusses a study that attempts to reach a better understanding of how the potential franchisees come to their decisions and attempts to compare this process with franchiser's perceptions. It initially focuses on the identification and on the decision-making process of French potential franchisees. Subsequently, applicants' answers are compared with those of the franchisers. Data were gathered at the annual franchise show, the Salon de la Franchise, held in Paris. Gap theory explains how differences from expectations between the service provider and the customer can affect the perceived quality of the franchise package. Questionnaires were given to potential franchisees and franchisers. The past experience of the potential franchisee is described with the typical items including age, experience, and educational qualifications. Potential franchisees' answers are reviewed. The study's results regarding the criteria employed in choosing the franchise format and in selecting a specific franchise are compared to those achieved by earlier empirical studies. This investigation portrays potential franchisees and suggests that they do follow an order of precedence in choosing a franchiser.ou

« Stops walking when talking » : 12 ans après

Prédire simplement et efficacement la chute du sujet âgé reste un objectif à atteindre. Il y a douze ans, Lundin-Olsson et al. publiaient une étude intitulée « Stops walking when talking as a predictor of falls in elderly people », montrant que s'arrêter de marcher lors d'une conversation prédisait la survenue d'une chute. Bien qu'une grande majorité d'études montre que les chuteurs ont des performances, en condition de double tâche, plus faibles que les non-chuteurs, il n'existe toujours pas de test clinique fiable, c'est-à-dire suffisamment sensible et spécifique, basé sur l'analyse des performances de la marche sous condition de double tâche permettant de prédire la chute. Les études publiées sur les relations entre les modifications de la marche, en condition de double tâche, et la survenue d'une chute sont rares et contradictoires. Les divergences sont probablement dues à un manque de puissance de certaines études, une mauvaise compréhension des modèles explicatifs des interférences observées sous double tâche, l'absence de prise en compte des facteurs de confusion tels qu'un déclin cognitif ou un état dépressif, et au fait que l'analyse des perturbations de la marche reposait sur l'œil du clinicien. Une meilleure compréhension de la nature des interférences, la standardisation des conditions de passation des tests, ainsi que l'utilisation des nouvelles techniques d'analyse spatio-temporelle de la marche permettront probablement le développement d'un test efficient. Par ailleurs, l'analyse des modifications des performances de la tâche attentionnelle semble être une nouvelle voie de recherche pertinente pour prédire la chute

Effets induits par une tâche attentionnelle sur la marche humaine (rôle respectifs de la variation de la vitesse de marche et de la charge attentionnelle sur la variabilité du pas)

La marche humaine est bien souvent considérée comme une activité motrice " automatique " qui dépend d'un contrôle sous-cortical et spinal, sous-entendant une faible participation des ressources attentionnelles, tout au moins chez l'adulte jeune. Avec l'âge, on observe une évolution des paramètres spatio-temporels de la marche liée à une modification de son contrôle, avec notamment la perte de son caractère automatique et la mise en jeu croissante des ressources attentionnelles. L'étude de la mise en jeu de l'attention dans la marche présente un intérêt tout particulier dans l'évaluation du risque de chute du sujet âgé et peut être réalisée via des paradigmes de double-tâche. Si les modifications de la valeur moyenne des paramètres spatio-temporels sont bien connues, leur variabilité d'un cycle à l'autre a été moins étudiée, alors qu'il s'agit d'un marqueur sensible du contrôle de la marche par le système nerveux central. Une forte variabilité du pas est le témoin de la mise en jeu du cortex sous la forme de ressources attentionnelles. Cependant des précautions doivent être prises dans l'interprétation de la valeur de la variabilité du pas car celle-ci peut également dépendre en partie de la vitesse de marche. Plusieurs études ont démontré que la variabilité du temps du pas augmentait lorsque la vitesse de marche diminuait. Hors, sous condition de double-tâche, la majorité des études montrent une réduction plus ou moins importante de la vitesse de marche. Ainsi, le travail de recherche que nous présentons a pour objectifs de répondre aux deux questions suivantes : 1) Quelle est l'influence de la vitesse de marche dans la valeur de la variabilité du temps du pas ? et 2) L'attention est-elle mise en jeu dans le contrôle du rythme de la marche chez le sujet jeune ? Pour répondre à ces deux questions, nous avons utilisé un paradigme de double-tâche combinant la marche à une tâche de décompte ou de fluence verbale, en analysant d'une part la performance à la tâche cognitive, et d'autre part la variabilité du temps du pas, en tenant compte de la vitesse du pas comme facteur de confusion potentiel. Quelque soit le groupe de sujets testés et la tâche cognitive utilisée, les résultats obtenus montrent une modification de la marche sous double-tâche avec notamment une réduction de la vitesse de marche (liée à l'augmentation du temps du pas) et une augmentation de la variabilité du temps du pas. Cette dernière, indépendante de la vitesse de marche, nous a permis de démontrer que le contrôle du caractère rythmique de la marche sollicite les ressources attentionnelles chez le sujet âgé, comme chez le sujet jeune.Human walking is considered as an automatic motor activity which is controlled by the subcortical and spinal regions, involving few attentional resources. Age-related changing of spatio-temporal gait parameters has been related to the loss of the automatic caracter of gait control and involvement of attentionnal control. The study of the relationship between attention and gait control is interesting to evaluate the risk of falls in older adults and may be obtained using dual-task paradigms. Mean gait parameters are well known, however, stride-to-stride variability has been less studied, in spite of the gait variability is a sensitive marker reflecting the control of gait by the CNS. A high variability is used as a clinical index of gait unsteadiness in relation with attentional control of the cortical regions. There are several validity concerns related to the methodology used to study locomotor control. The most common concern consists of the association of stride variability with stride velocity of the tested subjects. Stride velocity has been demonstrated to influence stride time variability. Because stride velocity often decreases under dual-task condition, the dual-task related increase in stride time variability therefore could be provoked by either the decrease in walking speed, the attention-demanding task itself, or both. Thus, the aims of this study is to answer to the following questions: 1) What is the influence of gait velocity on stride-to-stride variability? and 2) Is attention required to control the rhythmic steping mechanism of walking in helathy young adults? We used a dual-task paradigm, i.e. gait while backward counting or gait while verbal fluency task, and analysed both cognitive performance and gait parameters, adjusted for gait velocity. Whatever the subject's group and the nature of the attentional task tested, our results showed dual-task related changes, especially, gait velocity decrease (in relation with stride time increase), and stride time variability increase. This increased variability under dual-task was not related to the decrease of stride velocity, thus demonstrating the attentional control of the rhythmic stepping mechanism not only in older adults, but also in healthy young adults.ST ETIENNE-BU Médecine (422182102) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF