Understanding Variability in Older Adults using Inertial Sensors Rahul Soangra Dissertation submitted to the faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy In Biomedical Engineering Thurmon E. Lockhart Stefan M. Duma Karen A. Roberto Joel D. Stitzel Andrew R. Kemper May 05, 2014 Blacksburg, VA Keywords: Human Movement variability, frailty, inertial sensors © 2014 Rahul Soangra Understanding Variability in Older Adults using Inertial Sensors Rahul Soangra ABSTRACT Falls are the most frequent cause of unintentional injuries among older adults; afflicting 30 percent of persons aged 65 and older and more than 50 percent of persons aged 85 and older. There is a serious need for strategies to prevent falls in elderly individuals, but an important challenge in fall prevention is the paucity of objective evidence regarding the mechanisms that lead directly to falls. There exists no mechanisms about how to predict and manage elderly falls, which has multifactorial risk factors associated with its occurrence in the elderly. As the U.S. population continues to age, both the number of falls as well as the cost of treatment of fall injuries will continue to grow. Decades of research in fall prevention has not led to a decrease in the fall incidence; thus new strategies need to be introduced to understand and prevent falls. Aging reduces the adaptability of various physical and environmental stressors that hinder stability and balance maintenance and may therefore result in a fall. Movement variability in an individual’s task performance can be used to assess the limitations of the movement control system. Maintaining variation in movement engenders flexible and adaptable modalities for elderly individuals to prevent falls in an unpredictable and ever changing external environment. Conversely, excessive variability of movement may drive the control system closer to its stability limits during balance and walking tasks. Accordingly, inertial sensors are an emerging wearable technology that can facilitate noninvasive monitoring of fall prone individuals in clinical settings. This research examined the potential of inertial sensors for use in clinical settings, and evaluated their effectiveness in comparison to mature laboratory systems (i.e., force platform and camera system). Study findings showed a relationship between movement variability and fall risk among healthy young and older adults. Further, the outcomes of this work translates to the clinical environment to better understand the health status (leading to frailty) of cardiac patients; reflected by the underlying adaptability of the control system, but requires further improvements if to be used as robust clinical tool. This research provides the groundwork for rapid clinical assessments in which its validity and robustness should be investigated in future efforts. iii Acknowledgements This dissertation could not have been possible without continual support, guidance, and encouragement from a number of awesome people in my life. I am extremely grateful to my advisor and mentor Prof. Thurmon E. Lockhart for giving me an opportunity to work with him and believing in me and continuously encouraging me in the pursuit of this degree. The enthusiasm Dr. Lockhart brings to his work motivated me always to strive for excellence in all aspects. Funding for this dissertation was provided by National Institute of Health (R01 grant awarded to Dr. Lockhart) and National Science Foundation. I would also like to express hearty thanks to Cathy Jennings, Rebecca Clark and Dr. Joseph Baker in Carilion Roanoke Memorial Hospital. I would also like to extend my heartfelt thanks to my committee members: Prof. Stefan Duma, Dr. Andrew Kemper, Prof. Karen Roberto, and Prof. Joel Stitzel. Your guidance and feedback have been critical in improving my quality of research. My extra bit fluffy thanks to dear labmates Jian Zhang, Chris, Charlie, Peter, Jongsoon, Manutchanok, Xuefang, Selina, Nantakrit, Han, Prakriti and undergrad coworkers Ngoc, Seong, Amanda, Alejandra and my special thanks to Ahmed. I dedicate my dissertation work to my lovely daughter, Reetica Soangra. While working towards this degree I missed some lovely moments of life with my beloved daughter and wife but you both always increased my motivation in this journey. I also dedicate it to my dad Dr. M. C. Soangra and dad-in-law Dr. Dhanraj Dabi. They both have always inspired me to go for higher education. I could not have reached this phase of education without their unwarranted faith on me. My eternal gratitude goes to my mom Mrs. Sushila Soangra and my mom-in-law Mrs. Jasodha Dabi for their love, attention and caring. I can only say you all are great people. Numerous other people have contributed but my particular thanks to Anil ji, Alok ji, Raj ji, Rashmi Di, Ritu ji, Suman Di, Sameer and Saket ji. I‘ve saved the best until last: I don’t think there are words that exist to do justice to the thanks deserved by my wife Neetu. She had never ending supply of patience, love and support for me. I never forget, not even for a femtosecond, how lucky I am to have such a wonderful person as my life partner! iv Table of Contents ABSTRACT ............................................................................................................................. ii Acknowledgements .................................................................................................................. iv List of Figures ........................................................................................................................ viii List of Tables ............................................................................................................................. x CHAPTER 1: Overview .......................................................................................................... 1 Rationale ................................................................................................................................ 1 Specific Aims and Hypotheses .............................................................................................. 3 Study I: Laboratory Based Slip Study ................................................................................... 4 Study II: Laboratory Based Movement Variability Study using Inertial Sensors ................. 4 Study III: Clinical Study ........................................................................................................ 4 References ............................................................................................................................. 8 CHAPTER 2: Literature Review ......................................................................................... 10 An overview of falls in elderly persons ............................................................................... 10 Fall Risk Assessments ......................................................................................................... 11 Locomotion and attention .................................................................................................... 12 Dual Task and Gait Variability ........................................................................................ 16 Dual tasking in Alzheimer Disease Patients ........................................................................ 16 Dual Task in Older Fallers: ............................................................................................. 17 Dual tasking in Parkinson’s Disease Patients ...................................................................... 18 Energy Cost of walking ....................................................................................................... 18 Falls in Cardiovascular Disease Patients ............................................................................. 19 Factors Leading to Falls in Cardiovascular Disease Patients .............................................. 21 Frailty in CVD patients ....................................................................................................... 24 Mechanistic link between CVD and Frailty ........................................................................ 25 Physical Performance Measures and Frailty ....................................................................... 26 Assessment of Frailty .......................................................................................................... 27 References ........................................................................................................................... 29 CHAPTER 3: Dual-task does not increase slip and fall risk in healthy young and older adults....................................................................................................................................... 40 Abstract ............................................................................................................................... 40 Introduction ......................................................................................................................... 41 Objective of this study ..................................................................................................... 46 Materials and Methods ........................................................................................................ 46 Subjects ..........................................................................................................................