coordination in elderly geriatric patients
C.J.C. LAMOTHa1, F.J.A. VAN DEUDEKOMb, J.P. VAN CAMPENb, O.J. DE VRIESc, M. PIJNAPPELSd
aCenter for Human Movement Sciences, University Medical Centre Groningen, University of Groningen, the Netherlands
bDepartment of Geriatric Medicine, Slotervaart Hospital, Amsterdam, the Netherlands
c Department of Internal Medicine, VU Medical Center, Amsterdam, the Netherlands
d Research Institute MOVE, Faculty of Human Movement Sciences, VU University, Amsterdam, the Netherlands
Abstract. The effects of a cognitive dual task on gait coordination in 24 older geriatric day clinic patients while walking at self-selected speed was studied and related to cognitive function. Trunk accelerations were registered (DynaPort®; McRoberts) and used to calculate gait and trunk parameters. The Mini Mental State Examination and the Seven Minute Screen were administered. With dual task, walking speed was significantly lower, while variability of stride time increased and stability and regularity of lateral trunk accelerations decreased. These results provide support that changes in cognitive functions are likely to contribute to an increased fall risk.
Keywords. elderly walking; gait coordination; dual task; cognitive impairment.
1. Introduction
One in three community-dwelling persons over 65 years of age falls at least once a year and this rate increases with age and frailty. Major risk factors for falling are: gait and balance disorders, impaired vision and physical condition, cognitive impairment, gender and age1. Normal daily life activities often challenges to maintain balance and walking while performing concurrent (cognitive) dual tasks. Changes in gait characteristics during aging such as lower walking speed, reduced step length, increased step time have been interpreted as a more cautions gait pattern, adopted to decrease fall risk. A more conscious walking, however, may imply that walking requires more attention. Particularly in the frail elderly, changes in cognitive functions have been suggest to increase fall risk 2,3.
The aim of the present study was to examine the effect of a cognitive dual task in frail elderly on gait coordination and assess if such dual task effects on gait correlate with cognitive function. Specifically, stride variability and trunk accelerations patterns were studied as indicators of dynamic balance ability during walking.
1 Corresponding Author.
Rehabilitation: Mobility, Exercise and Sports L.H.V. van der Woude et al. (Eds.)
IOS Press, 2010
© 2010 The authors and IOS Press. All rights reserved.
doi:10.3233/978-1-60750-080-3-131
131
2. Methods
Twenty four elderly persons (age=80.9±3.6 years, men/women 9/15) were recruited from the geriatric day clinic of the Slotervaart hospital in Amsterdam. In all participants the Mini Mental State Examination (MMSE) and the Seven Minute Screen (SMS) were administered to evaluate cognitive functions. The MMSE was used to divide participants into two groups: people with an indication of cognitive impairment (CI; MMSE<23; N=12) and people without cognitive impairment (CNI; MMSE>26;
N=12).
Participants walked 100 meter at self-selected speed, once without and once while performing a verbal dual task: citing words starting with the letter “R” or “G”. The verbal dual task was also performed during sitting. When walking, trunk accelerations in 3 orthogonal directions were measured with a tri-axial piezo-capacitive accelerometer (DynaPort®MiniMod, McRoberts BV, The Hague, the Netherlands), fixed with an elastic belt at the level of lumbar segment L3. Data were sampled at 100 Hz.
Data and statistical analyses
Anterior-posterior (AP) and medio-lateral (ML) acceleration time-series were analyzed.
Outcome measures during walking with and without dual task were:
• Gait parameters: walking speed, stride frequency (SF), mean and coefficient of variation (CV) of stride times, the scaling-exponent α to examine the time dependent variability of stride times, and the phase variability index (PVI) as a measure of the variability of the coordination between right and left steps.
• Trunk ML and AP acceleration parameters4: the root mean squares (RMS), the harmonicity ratio (HR) as an index of smoothness of the accelerations, the scaling-exponent α to assess time dependent variations in accelerations, and the maximum Lyapunov exponent (λmax) to index local stability.
• The performance on the DT, the MMSE and the SMS tests.
Wilcoxon-signed rank test was applied to examine the effect of dual tasking on stride and trunk acceleration parameters. Differences between the CI group and CNI group were analysed with the Mann-Whitney U-test. To examine the relation between cognitive function, MMSE scores and gait and trunk parameters, Spearman correlations were calculated.
3. Results
Under dual task conditions, walking speed and SF decreased significantly (P < 0.01), while the scaling-exponent α of stride times and the PVI increased significantly (P <
0.01). Dual tasking significantly decreased the RMS, the scaling exponent α, λmax and the HR of AP and ML trunk accelerations (all P <0 .01), indicating a lower amplitude, loss of local stability and decreased smoothness of accelerations, respectively.
A significant group effect was found on the RMS (P = 0.03), scaling-exponent α of ML accelerations (P < 0.01), the scaling-exponent α of stride times (P = 0.03),.and the PVI (P = 0.04) (see Figure 1).
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Figure 1. Differential effects of dual tasking on gait and trunk variables on both groups
Overall, correlations between MMSE, SMS scores and gait and trunk acceleration measures were low (r<0.3). Variability (α) of trunk accelerations correlated significantly, but moderately with SMS (α ML, r=0.51, α AP, r=-0.35) and MMSE values (α ML, r=0.36). Within the CI group, the associations were higher for several measures (Table 1).
Table 1: Spearman correlation values between SMS test scores, the MMSE values and gait and trunk acceleration parameters within the CI group (N=12). ** P <0.01; * P <0.05
SMS Speed Stride RMS HR λmax acc.
Mean CV PVI AP AP AP
SMS .62** .52* .36* -.66** -.46* .63* -35
MMSE .70** .71** .68** .71** .68** .61** -.68** .69**
4. Conclusion
Despite the reduced walking speed during dual tasking, trunk accelerations patterns were more irregular and variable, especially in cognitive impaired subjects. For the cognitive impaired group, an association between cognitive function and several gait parameters was observed. Although the slowing of gait while performing a dual task could reflect an adaptation to more difficult circumstances, the resulting trunk adaptations were a significant consistent instability factor, suggesting an increased fall risk. The results of the present study provide further support that changes in cognitive functions are likely to contribute to an increased fall risk, especially when combining balance or walking tasks with concurrent (cognitive) tasks. Fall management should consist of a combination of identification and treatment of the underlying causes of physiological and cognitive impairments.
MP was financially supported by NWO grant # 916.76.077.
References
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