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The Effect of Higher Order Listening Function and Hearing Loss on Cognition

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The Effect of Higher Order Listening Function and Hearing Loss on Cognition THE EFFECT OF HIGHER ORDER LISTENING FUNCTION AND HEARING LOSS ON COGNITION IN OLDER ADULTS GRACE KELLEE NIXON ORCID 0000-0002-4106-6554 Submitted in total fulfilment of the requirements of the degree of Doctor of Philosophy January 2020 Department of Audiology and Speech Pathology The University of Melbourne i ii © 2020 GRACE KELLEE NIXON ALL RIGHTS RESERVED iii iv ABSTRACT Grace Kellee Nixon: The Effect of Higher Order Listening Function and Hearing Loss on Cognition in Older Adults INTRODUCTION: Previous research has identified a relationship between hearing loss and cognitive impairment/dementia in older adults, however this research has primarily focused on measures of sensorineural hearing loss (SNHL). Central Auditory Processing (CAP), an ability which decreases with increasing age, is recognised as important for understanding speech in background noise, but is not routinely considered in audiological assessment or hearing-cognition research. Yet, some studies have provided evidence that poorer performance on some measures of CAP ability significantly relate to reduced cognitive function and/or increased likelihood of dementia diagnosis. Although there is no known treatment for cognitive impairment, hearing impairment is to some extent treatable with hearing aids (HAs). OBJECTIVES: This study aimed to examine the relationship between hearing impairment and cognitive impairment by assessing both peripheral hearing loss and CAP ability. Additionally, this research aimed to investigate how hearing, cognition and personal factors influence HA outcomes (uptake/use/benefit) in older adults. DESIGN: Experimental study design with 85 older adults between the ages of 60.33 and 80.08 (m =70.23, SD = 5.17). SNHL was assessed using Pure Tone Audiometry (PTA), the Listening in Spatialised noise-Sentences (LiSN-S) test and Dichotic Digits Test. Cognition was measured using the Cogstate Brief Battery. Personal factors were recorded from participant’s answers on a series of take-home v questionnaires. Hearing aid benefit and use was subjectively reported at three- and six-months post HA fitting. RESULTS: Results for three of the four LiSN-S conditions shared a significant correlation with at least one cognitive measure, and SNHL was also significantly related to two cognitive domains (attention and executive function) in this cohort. Those who decided to use HAs had significantly poorer hearing as measured by both PTA and the LiSN-S test, and those with poorer hearing reported greater HA benefit. Lastly, stronger psychomotor function was associated with greater reported use of HAs at three- and six-months post HA fitting. Greater family interaction and attention scores also were associated with greater HA use at three- and six-months post fitting respectively. IMPLICATIONS: The older hearing-impaired patient may present with a combination of hearing loss, decreased auditory processing ability and impaired cognitive ability. It may be prudent to consider the presence and possible interactions of multiple health conditions as well as psychosocial factors when determining the appropriate management pathway for and expectations of the patient. Future research should investigate longitudinal cognitive implications for patients presenting with a SP deficit. Also, for older adults presenting with a SP deficit, the benefits of early referral for cognitive assessment should be considered. Moreover, a combination of hearing, cognitive and psychosocial factors impact HA outcomes in older Australians. These factors should be considered in audiological rehabilitation to best maximise patient HA outcomes, and further research should consider the long-term clinical implications HA fitting has on natural cognitive decline in the elderly. vi vii Mum, your love of literature, and Dad, your scientific mind - was an inevitable catalyst for writing a thesis. To my Parents, Julie and Stuart. For your unwavering support, in every aspect of life. For giving me the opportunities, you never had yourselves. viii DECLARATION (i) the thesis comprises only my original work towards the Doctor of Philosophy except where indicated in the preface; (ii) due acknowledgement has been made in the text to all other material used; (iii) the thesis is fewer than 100,000 words in length, exclusive of tables, maps, bibliographies and appendices. January 2020 ________________________ Grace Kellee Nixon ix PREFACE This dissertation is my original, independent work and, to the best of my knowledge, contains no material written by another person, except where due acknowledgement has been made. The PhD candidate, Grace Kellee Nixon, was responsible for the development, preparation, and execution of the dissertation. The contribution of others as co- authors on publications is as follows: Julia Sarant assisted with critical revisions for all four publications presented in Chapters: 2.2, 5, 6.2 and 7. Dani Tomlin assisted with revision for all four publications presented in Chapters: 2.2, 5, 6.2 and 7; and Richard Dowell provided assistance with statistical analysis and revision for three publications pertaining to experiments 1, 2 and 3 (Chapters 5, 6.2 and 7). The publication status for each of the results chapters is outlined below: Chapter 2.2 Published in the International Journal of Audiology, March 2019 Chapter 4 Unpublished material not submitted for publication Chapter 5 Published in the International Journal of Audiology, July 2019 Chapter 6 Submitted for publication to American Journal of Audiology, January 2020 Chapter 7 Submitted for publication to Journal of Speech, Language and Hearing Research, January 2020 x ACKNOWLEDGEMENTS This work, and the previous few years which I have truly enjoyed, were made possible by many important people. Firstly, I would like to thank the University of Melbourne and Fay Marles Scholarship which supports disadvantaged women. Secondly, I have incredible appreciation to those who have encouraged me and provided me with creature comforts and love during this venture. This includes all my dearest friends and family of whom I could not possible name and thank enough, even within the word-count of a thesis. I would however like to acknowledge my now-husband Matt. You supported my decision to do my Masters, and then my PhD, and even committed yourself to marrying me in the process. You are also part of a loving home with our fur-children, whom made the end of a long day amazing every-time. To my University-turn-work bestie Joc, the long days were made possible and tolerable because of you. For every bubble-tea run, agreeing rant, and early morning, I will always be thankful. I do not know where to begin with thanking my supervisors. Richard, for remaining calm during the repetitive emails and stats advice, I am incredibly grateful. Big Bear – where do I start? Julia, you have provided me with so many lessons that extend beyond an academic career. Your door was not only open to questions regarding my PhD, but to anything (big or small) that you were able to help with. Thank-you. Dani, this journey would never have begun without your initial guidance and encouragement. You helped me down this path that I would never have thought I was capable of following. Not only that, but you walked with me every step of the way. xi To the participants who kindly gave their time and made this project possible, I owe you my most sincere gratitude. Lastly, to my two first ‘pilot’ participants, Nan and Pop, thank-you for everything. I love you. xii Table of Contents LIST OF TABLES AND FIGURES .............................................................. XVII ACRONYMS ..................................................................................................XIX CHAPTER 1 INTRODUCTION ......................................................................... 1 1.1 PURPOSE ............................................................................................... 1 1.2 BACKGROUND ..................................................................................... 1 1.3 OVERVIEW OF THIS RESEARCH ........................................................ 6 1.3.1 Study 1: The Relationship between Peripheral Hearing Loss, Higher Order Listening Function and Cognition in Older Australians. ..................... 7 1.3.2 Study 2: Spatial Processing Ability and Executive Function in Older Australians. .................................................................................................. 7 1.3.3 Study 3: Hearing Aid Uptake, Benefit and Use: The Impact of Hearing, Cognition and Personal Factors ...................................................... 9 1.4 OVERALL AIM ...................................................................................... 9 1.5 SUMMARY AND SIGNIFICANCE ........................................................ 9 CHAPTER 2 LITERATURE REVIEW ..............................................................12 2.1 OUTLINE ..................................................................................................12 2.2 THE AGING BRAIN: THE HEARING-COGNITIVE LINK ...............................13 2.2.1. Foreword ...........................................................................................13 2.2.2 The Aging Brain .................................................................................14 2.2.3 The Aging Auditory System ...............................................................17 2.2.4. The Hearing Brain .............................................................................22 2.3 NARRATIVE
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