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The Journals of Gerontology Series A: Biological Sciences and Medical Sciences Advance Access originally published online on August 13, 2009
The Journals of Gerontology Series A: Biological Sciences and Medical Sciences 2009 64A(12):1304-1311; doi:10.1093/gerona/glp113
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© The Author 2009. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org.

Frailty and the Degradation of Complex Balance Dynamics During a Dual-Task Protocol

Hyun Gu Kang1,2,3,4,*, Madalena D. Costa2,3,5,*, Attila A. Priplata6, Olga V. Starobinets1, Ary L. Goldberger2,5, Chung-Kang Peng2,5, Dan K. Kiely1, L. Adrienne Cupples7,8 and Lewis A. Lipsitz1,2,3

1 Institute for Aging Research, Hebrew SeniorLife, Boston, Massachusetts
2 Harvard Medical School, Boston, Massachusetts
3 Division of Gerontology, Beth Israel Deaconess Medical Center, Boston, Massachusetts
4 Department of Biomedical Engineering, Boston University, Massachusetts
5 Division of Interdisciplinary Medicine and Biotechnology, Beth Israel Deaconess Medical Center, Boston, Massachusetts
6 Stryker Corporation, Cambridge, Massachusetts
7 Department of Biostatistics
8 Department of Epidemiology, Boston University, Massachusetts

Address correspondence to Hyun Gu Kang, PhD, Institute for Aging Research, Hebrew SeniorLife, 1200 Centre Street, Boston, MA 02131. Email: hyungukang{at}hrca.harvard.edu


  Abstract

Background: Balance during quiet stance involves the complex interactions of multiple postural control systems, which may degrade with frailty. The complexity of center of pressure (COP) dynamics, as quantified using multiscale entropy (MSE), during quiet standing is lower in older adults, especially those with falls. We hypothesized that COP dynamics from frail elderly individuals demonstrate less complexity than those from nonfrail elderly controls; complexity decreases when performing a dual task; and postural complexity during quiet standing is independent of other conventional correlates of balance control, such as age and vision.

Methods: We analyzed data from a population-based study of community-dwelling older adults. Frailty phenotype (nonfrail, prefrail, or frail) was determined for 550 participants (age 77.9 ± 5.5 years). COP excursions were quantified for 10 trials of 30 seconds each. Participants concurrently performed a serial subtraction task in half of the trials. Complexity of balance dynamics was quantified using MSE. Root-mean-square sway amplitude was also computed.

Results: Of the 550, 38% were prefrail and 9% were frail. Complexity of the COP dynamics in the anteroposterior direction was lower in prefrail (8.78 ± 1.91 [mean ± SD]) and frail (8.38 ± 2.13) versus nonfrail (9.20 ± 1.74) groups (p < .001). Complexity reduced by a comparable amount in all three groups while performing the subtraction task (p < .001). Quiet standing complexity was independently associated with frailty after adjusting for covariates related to balance while sway amplitude was not.

Conclusion: Cognitive distractions during standing may further compromise balance control in frail individuals, leading to an increased risk of falls.

Keywords Aging; Frailty; Dual task; Posture control; Complexity

Received: December 8, 2008; Accepted: July 2, 2009

* These two authors contributed equally to this work.

Decision Editor: Luigi Ferrucci, MD, PhD


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