EPL, 77 (2007) 68008
DOI: 10.1209/0295-5075/77/68008

Noise and poise: Enhancement of postural complexity in the elderly with a stochastic-resonancebased therapy

M. Costa¹, A. A. Priplata^{2, 3}, L. A. Lipsitz², Z. Wu⁴, N. E. Huang⁵, A. L. Goldberger¹ and C.-K. Peng<sup>1

1</sup>  Division of Interdisciplinary Medicine and Biotechnology, Beth Israel Deaconess Medical Center, Harvard Medical School - 330 Brookline Avenue, Boston, MA 02215, USA
²  Hebrew SeniorLife, Institute for Aging Research, Division of Gerontology, Beth Israel Deaconess Medical Center - 1200 Center Street, Boston, MA 02215, USA
³  Center for BioDynamics and Department of Biomedical Engineering, Boston University - 111 Cummington Street, Boston, MA 02215, USA
⁴  Center for Ocean-Land-Atmosphere Studies - 4041 Powder Mill Road, Suite 302, Calverton, MD 20705, USA
⁵  Research Center for Adaptive Data Analysis, National Central University - Chungli, Taiwan, ROC

received 3 November 2006; accepted in final form 2 February 2007; published March 2007
published online 6 March 2007

Abstract
Pathologic states are associated with a loss of dynamical complexity. Therefore, therapeutic interventions that increase physiologic complexity may enhance health status. Using multiscale entropy analysis, we show that the postural sway dynamics of healthy young and healthy elderly subjects are more complex than that of elderly subjects with a history of falls. Application of subsensory noise to the feet has been demonstrated to improve postural stability in the elderly. We next show that this therapy significantly increases the multiscale complexity of sway fluctuations in healthy elderly subjects. Quantification of changes in dynamical complexity of biologic variability may be the basis of a new approach to assessing risk and to predicting the efficacy of clinical interventions, including noise-based therapies.

PACS
89.75.-k - Complex systems.
87.19.La - Neuroscience.
05.45.Tp - Time series analysis.

© Europhysics Letters Association 2007