Gilles Allali

Stops walking when talking: a predictor of falls in older adults?

The objective of this study was to systematically review all published articles examining the relationship between the occurrence of falls and changes in gait and attention‐demanding task performance whilst dual tasking amongst older adults. An English and French Medline and Cochrane library search ranging from 1997 to 2008 indexed under ‘accidental falls’, ‘aged OR aged, 80 and over’, ‘dual task’, ‘dual tasking’, ‘gait’, ‘walking’, ‘fall’ and ‘falling’ was performed. Of 121 selected studies, fifteen met the selection criteria and were included in the final analysis. The fall rate ranged from 11.1% to 50.0% in retrospective studies and from 21.3% to 42.3% in prospective ones. Amongst the three retrospective and eight prospective studies, two and six studies, respectively, showed a significant relationship between changes in gait performance under dual task and history of falls. The predictive value for falling was particularly efficient amongst frail older adults compared with healthy subjects. Two prospective studies challenged the usefulness of the dual‐task paradigm as a significant predictor compared to single task performance and three studies even reported that gait changes whilst dual tasking did not predict falls. The pooled odds ratio for falling was 5.3 (95% CI, 3.1–9.1) when subjects had changes in gait or attention‐demanding task performance whilst dual tasking. Despite conflicting early reports, changes in performance whilst dual tasking were significantly associated with an increased risk for falling amongst older adults and frail older adults in particular. Description of health status, standardization of test methodology, increase of sample size and longer follow‐up intervals will certainly improve the predictive value of dual‐task‐based fall risk assessment tests.

Vitamin D and cognitive performance in adults: a systematic review

Chronic low serum 25‐hydroxyvitamin D (25OHD) concentrations are common in adults and are associated with numerous non‐skeletal diseases. Vitamin D receptors (VDR) are located in the human cortex and hippocampus, which are key areas for cognition. The objective of this study was to systematically review all published data from the past 30 years which examined the association between serum 25OHD concentrations and cognitive performance in adults. An English and French Medline, PsycINFO® and Cochrane Library search ranging from 1979 to 2008 indexed under the Medical Subject Heading (MeSH) terms ‘Vitamin D’ or ‘Hydroxycholecalciferols’ combined with the terms ‘Dementia’ or ‘Cognition’ or ‘Cognition Disorders’ or ‘Delirium’ or ‘Memory’ or ‘Memory Disorders’ or ‘Orientation’ or ‘Executive Functions’ or ‘Attention’ or ‘Brain’ or ‘Neuropsychological Tests’ was performed. Of the 99 selected studies, five observational studies met the selection criteria and were included in the final analysis. No prospective cohort study was found. The number of participants ranged from 32 to 9556 community‐dwelling older adults (45–65% women). Three studies showed four significant positive associations between serum 25OHD concentrations and global cognitive functions, whereas three other studies exploring specific aspects of cognition showed 11 non‐significant associations. This systematic review shows that the association between serum 25OHD concentrations and cognitive performance is not yet clearly established. The inconclusive results of the reviewed studies could be due to methodology, types of the cognitive tasks used and/or the cellular mechanisms of vitamin D.

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.

Recurrent falls and dual task-related decrease in walking speed: is there a relationship?

OBJECTIVES: To determine whether dual task–related changes in walking speed were associated with recurrent falls in frail older adults.

Gait variability among healthy adults : low and high stride-to-stride variability are both a reflection of gait stability

Background: It has been suggested that high stride-to-stride variability (STV) is a reflection of gait instability. However, both low and high STV has been shown in fallers and in nonfallers; therefore, the interpretation of STV of spatiotemporal gait parameters remains difficult. Thus, we sought to characterize and compare STV of spatial and temporal stride parameters among young and older healthy adults, and to determine the extent to which opposite results in STV could provide similar implications in terms of gait stability. Methods: Mean values of coefficients of variation of spatiotemporal gait parameters were collected from 30 young adults (14 men and 16 women; mean age 28.1 ± 6.0 years) and 33 older adults (2 men and 31 women; mean age 74.4 ± 7.1 years) walking at self-chosen normal walking speed over a GAITRite® System. Results: An age-related increase in STV was only observed with stride width (p = 0.012), whereas increased stride length and stance time variability in older adults were related to decreased walking speed (p = 0.006 and p = 0.018). In addition, both low and high STV was found in both groups of subjects and the highest value was observed for stride width (p < 0.001). Conclusion: The two main implications of the present results are that decreased walking speed should be taken into account when exploring age-related effects on gait variability, and that both low and high spatiotemporal STV may reflect gait stability in healthy adults.

Walking speed-related changes in stride time variability: effects of decreased speed

BackgroundConflicting results have been reported regarding the relationship between stride time variability (STV) and walking speed. While some studies failed to establish any relationship, others reported either a linear or a non-linear relationship. We therefore sought to determine the extent to which decrease in self-selected walking speed influenced STV among healthy young adults.MethodsThe mean value, the standard deviation and the coefficient of variation of stride time, as well as the mean value of stride velocity were recorded while steady-state walking using the GAITRite® system in 29 healthy young adults who walked consecutively at 88%, 79%, 71%, 64%, 58%, 53%, 46% and 39% of their preferred walking speed.ResultsThe decrease in stride velocity increased significantly mean values, SD and CoV of stride time (p < 0.001), whereas the repetition of trials (p = 0.534, p = 0.177 and p = 0.691 respectively for mean, SD, CoV); and step asymmetry (p = 0.971, p = 0.150 and p = 0.288 for mean, SD and CoV) had no significant effect. Additionally, the subjects effect was significant for all stride parameters (p < 0.001). The relationship between a decrease in walking speed and all stride parameters (i.e., mean values, SD and CoV of stride time) was significantly quadratic and showed higher STV at a slow speed (p < 0.001).ConclusionThe results support the assumption that gait variability increases while walking speed decreases and, thus, gait might be more unstable when healthy subjects walk slower compared with their preferred walking speed. Furthermore, these results highlight that a decrease in walking speed can be a potential confounder while evaluating STV.

Impact of impaired executive function on gait stability

Background: Executive dysfunction contributes to gait changes, but the precise mechanisms are still poorly understood. Dual-task-related gait changes depend in part on the capacity to appropriately allocate attention between tasks performed simultaneously and are mainly related to executive deficits. This study aimed to describe the impact of dysexecutive function on gait stability in subjects with dementia using dual tasking. Methods: Mean values and coefficients of variation of stride time while only walking and while walking and backward counting (dual tasking) were measured using the GAITRite® System in 18 subjects with dementia and impaired executive function (IEF), in 16 subjects with dementia and intact executive function, and in 22 nondemented subjects as controls. Results: Stride time, and particularly its variability, significantly increased while performing dual tasking (p < 0.05). IEF was related to both stride time and stride time variability during walking only and to even more gait changes, while dual tasking compared to nondemented subjects and demented subjects without IEF. Conclusions: These findings confirm the role of executive function in dual tasking, but also strongly suggest their importance for gait stability.

Blood pressure levels and brain volume reduction: a systematic review and meta-analysis.

Objective: High blood pressure (BP) levels may be associated with brain volume reduction and may contribute to brain atrophy in key brain regions involved in cognition and susceptible to neurodegeneration in Alzheimers disease. The purpose of this work was to systematically review and quantitatively synthesize the association of BP levels with brain volume reduction in humans. Methods: An English Medline, Cochrane Library and PsycINFO search was conducted in June 2012 using the Medical Subject Heading terms ‘Blood pressure’, ‘Hypertension’, ‘Brain mapping’ and ‘Brain atrophy’. Results: Of the 609 screened abstracts, 28 studies (4.6%) were included in the qualitative analysis. Twenty-six studies (92.9%) showed a significant association of higher BP levels and/or hypertension with total and/or regional brain volume reduction, the frontal and temporal lobes being particularly affected. In addition, four other studies reported an association between lower BP levels and brain volume reduction. Due to the heterogeneity of methodology and outcomes, random-effects meta-analyses of the mean difference of brain volume could be performed on only seven studies, with a total of 709 cases with hypertension and 1001 controls without hypertension. The findings showed no between-group difference regarding the whole-gray matter volume (summary mean difference = 2.42 cm3 [95% confidence interval (CI): −2.13 to 6.96]). Conversely, cases with hypertension exhibited lower hippocampus volume compared with controls [summary mean difference = −0.10 cm3 (95% CI: −0.17 to −0.02)]. Conclusion: These findings provide evidence that high BP levels lead to brain volume reduction, specifically in hippocampus, and may be an important factor that contributes to neurodegeneration in Alzheimers disease.

Imagined Timed Up & Go test: a new tool to assess higher-level gait and balance disorders in older adults?

BACKGROUND Few studies have explored motor imagery (MI) as a way of accessing the higher-level of control of complex body movements involved in gait or balance. The objective of this study was 1) to measure and compare the time needed to complete the Timed Up & Go test (TUG), the time needed to imagine performing the same test (iTUG) and to calculate the time difference between both of these conditions (delta time) in a sample of young and older adults, and 2) to examine whether there was an association between the Timed Up & Go test results (TUG, iTUG, delta time), age and cognitive decline. METHODS A total of 162 subjects (38 healthy young adults, mean age 25.7+/-2.3 years, 73.7% women and 124 older inpatients, mean age 85.3+/-6.5 years, 76.6% women) were included in this cross-sectional study. The mean+/-SD of TUG, iTUG and delta time, age and the Mini Mental State Examination (MMSE) score were used as main outcomes. RESULTS Age was associated with an increase in time of TUG (P<0.001) and of delta time (P=0.015), and with a decrease in time of iTUG (P<0.001), whereas cognitive decline was only associated with increase in delta time (P=0.030). There was an increase in time of TUG (P<0.001) and in delta time (P<0.001) for subjects who used a walking aid. The increase in delta time depended on the MMSE score when the subjects did not use a walking aid (P for trend=0.001). CONCLUSIONS iTUG is clinically feasible among frail older adults and may quickly inform any clinician about higher-level changes in control of gait and balance in older adults.

Vitamin D insufficiency and mild cognitive impairment: cross-sectional association.

Background:  Low serum 25‐hydroxyvitamin D (25OHD) concentrations have been associated with dementia. The association with mild cognitive impairment (MCI) has not yet been explored. Our aim was to examine the association between vitamin D status and MCI status amongst older community‐dwellers with subjective memory complaint.