Comparing Postural Stability Entropy Analyses to Differentiate Fallers and Non-fallers
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The health and financial cost of falls has spurred research to differentiate the characteristics of fallers and non-fallers. Postural stability has received much of the attention with recent studies exploring various measures of entropy. This study compared the discriminatory ability of several entropy methods at differentiating two paradigms in the center-of-pressure of elderly individuals: (1) eyes open (EO) vs. eyes closed (EC) and (2) fallers (F) vs. non-fallers (NF). Methods were compared using the area under the curve (AUC) of the receiver-operating characteristic curves developed from logistic regression models. Overall, multiscale entropy (MSE) and composite multiscale entropy (CompMSE) performed the best with AUCs of 0.71 for EO/EC and 0.77 for F/NF. When methods were combined together to maximize the AUC, the entropy classifier had an AUC of for 0.91 the F/NF comparison. These results suggest researchers and clinicians attempting to create clinical tests to identify fallers should consider a combination of every entropy method when creating a classifying test. Additionally, MSE and CompMSE classifiers using polar coordinate data outperformed rectangular coordinate data, encouraging more research into the most appropriate time series for postural stability entropy analysis.
KeywordsEntropy RQA Fallers Elderly Sample entropy Multiscale entropy Approximate entropy Composite multiscale entropy
Importantly, the authors want to thank Dr. Rahul Soangra, Dr. Han Yeoh, Dr. Jian Zhang, and Chris Frames, for collecting data, providing advice, and general troubleshooting, and Nora Fino for statistical consultation. This research was also supported by NSF-Information and Intelligent Systems (IIS) and Smart and Connected Health—1065442 and 1065262. The first author (PCF) was supported by a NSF Graduate Research Fellowship under Grant No. DGE 0822220. This comparative analysis was originally inspired by a project-based course exploring the frontiers of dynamical systems research, conducted by SDR under NSF Grant 1150456. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of NSF.
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