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Hearing Impairment, Cardiovascular Disease Risk Factors HEARING IMPAIRMENT, CARDIOVASCULAR DISEASE RISK FACTORS, METHYLMALONIC ACID, AND VITAMIN B 12 STATUS IN OLDER ADULTS by SOHYUN PARK (Under the Direction of Mary Ann Johnson, Ph.D.) ABSTRACT Hearing impairment is a common chronic health condition in older adults and is associated with impaired quality of life. However, there is limited comprehensive research concerning interactions among poor diets and hearing loss. In the first study, the prevalence of hearing impairment and the relationship of Hearing Handicap Inventory for the Elderly with pure-tone average threshold (PTA) were evaluated. Approximately 63% of participants had hearing impairment in the best ear [PTA across 1, 2, and 4 kHz > 25 dB hearing level (HL)]. A moderate correlation was found between Hearing Handicap Inventory for the Elderly and PTA. In the second study, the relationship between hearing loss and cardiovascular disease (CVD) risk factors was examined. Low-density lipoprotein cholesterol, total cholesterol, and triglycerides were not significantly associated with hearing loss. However, PTA was significantly correlated with high-density lipoprotein (HDL) cholesterol in the poorest ear and total cholesterol/HDL cholesterol ratio in both ears. Participants with impaired hearing had significantly lower HDL cholesterol concentration than those with normal hearing ( ≤ 25 dB HL) in the worst ear. Participants with PTA > 40 dB HL had significantly lower HDL cholesterol level than those with PTA ≤ 40 dB HL in both ears. Thus, HDL cholesterol may be a modifiable risk factor for hearing loss. In the third study, the relationship between age-related hearing loss (ARHL) and poor vitamin B 12 status in older adults was examined, using multiple measures of vitamin B 12 status and by repletion with a vitamin B 12 supplement. A consistent relationship of vitamin B 12 with auditory function was found in the worst ear. Participants with impaired hearing in the worst ear had a significantly higher prevalence of vitamin B12 deficiency, higher mean serum MMA concentration, higher prevalence of elevated MMA (> 271 nmol/L), and a non- significantly higher prevalence of low serum vitamin B 12 than those with normal hearing (≤ 25 dB HL). Hearing thresholds were not improved in any group after three months of vitamin B 12 supplementation (0-1000 µg/d). Impaired vitamin B 12 status may be a modifiable risk factor for ARHL in older adults. Since vitamin B 12 repletion did not improve hearing function in vitamin B12 deficient participants, this suggests that prevention of vitamin B 12 deficiency may be important. This research adds to the growing body of literature that suggests CVD- and nutrition-related risk factors are associated with hearing loss in older people. INDEX WORDS: Vitamin B 12 , Methylmalonic acid, Intervention, Hearing loss, CVD risk factors, Older adults HEARING IMPAIRMENT, CARDIOVASCULAR DISEASE RISK FACTORS, METHYLMALONIC ACID, AND VITAMIN B 12 STATUS IN OLDER ADULTS by SOHYUN PARK B.S., The Kosin University, South Korea, 1998 M.S., The Sookmyung Women’s University, South Korea, 2000 A Dissertation Submitted to the Graduate Faculty of The University of Georgia in Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY ATHENS, GEORGIA 2006 © 2006 Sohyun Park All Rights Reserved HEARING IMPAIRMENT, CARDIOVASCULAR DISEASE RISK FACTORS, METHYLMALONIC ACID, AND VITAMIN B 12 STATUS IN OLDER ADULTS by SOHYUN PARK Major Professor: Mary Ann Johnson, Ph.D. Committee: Mary Ann Johnson, Ph.D. Albert R. De Chicchis, Ph.D. Joan G. Fischer, Ph.D. Arthur Grider, Ph.D. James L. Hargrove, Ph.D. Electronic Version Approved: Maureen Grasso Dean of the Graduate School The University of Georgia May 2006 iv DEDICATION I would like to dedicate this achievement to my parents, Sungman Park and Malpil Lee, for their unconditional love and immeasurable support. My achievement of this higher degree would not have been possible without them. With this opportunity, I would like to let my parents know how much I love them and appreciate their sacrifice. I would also like to dedicate this accomplishment to my husband Antonio, my family, and my friends, for their love, encouragement, and unfailing support of my advanced education. Their love and support have sustained me during this long journey. Thank you all! 감사의 글 오늘이 있기까지 헌신적인 사랑으로 저에게 모든 것을 베풀어 주신 사랑하는 나의 부모님 ( 아버지 박성만님 과 어머니 이말필님)께 박사과정의 결실인 이 논문을 받칩니다. 부모님의 헌신적인 사랑, 희생, 그리고 뒷받침 없이는 오늘의 결실이 없다고 해도 과언이 아닙니다. 이 기회를 통해, 부모님께 제가 얼마나 부모님을 사랑하고, 존경하고, 그리고 부모님의 희생에 감사 드리는지를 진심으로 전하고 싶습니다. 사랑, 격려, 그리고 응원을 해준 사랑하는 나의 남편 ( 안토니오), 가족들, 친구들, 그리고 교수님들에게 이 결실을 받칩니다. 박사과정 기간 동안 사랑으로 나를 격려해 주신 모든 분들께 이 결실을 드리면서 기쁨을 함께 하고자 합니다. 정말 감사 드립니다. 2006 년 5 월 박 소 현 올림 v ACKNOWLEDGEMENTS I would like to extend a sincere thank you to my committee members: Dr. Mary Ann Johnson, Dr. Albert R. De Chicchis, Dr. Joan G. Fischer, Dr. Arthur Grider, and Dr. James L. Hargrove for their professional advice and guidance. I would like to give a very special thank you to my major professor, Dr. Mary Ann Johnson, for her steady support, encouragement, and assistance during completion of this dissertation and throughout my graduate school education. I would like to thank the people who collaborated on this project and helped in data collection, analysis, and editing: Dr. Sally P. Stabler, Dr. Kelly Shea-Miller, Dr. Robert J. Nozza, Dr. Robert H. Allen, Dr. Dorothy B. Hausman, Evelyn Dolce, Nikki Hawthorne, Jean Edmonds, Nancy Omdahl, and Tiffany Sellers. I would also like to thank my wonderful fellow graduate students and friends for your friendship, laughter, and willingness to help me throughout my graduate training. Thank you so much. vi TABLE OF CONTENTS Page ACKNOWLEDGEMENTS.............................................................................................................v LIST OF TABLES......................................................................................................................... ix LIST OF FIGURES ....................................................................................................................... xi CHAPTER 1 INTRODUCTION .........................................................................................................1 References .................................................................................................................5 2 LITERATURE REVIEW ..............................................................................................8 Background and Significance....................................................................................8 Purpose ......................................................................................................................9 The Human Auditory System..................................................................................10 Assessment of Auditory Function ...........................................................................15 The Biological Basis of Hearing Loss in Older Adults...........................................18 The Prevalence of Hearing Loss .............................................................................20 Hearing Loss and Quality of Life in Older Adults..................................................21 Risk Factors for Hearing Loss.................................................................................22 Functions of Vitamin B 12 ........................................................................................41 Biomarkers for Vitamin B 12 Status .........................................................................43 Defining Vitamin B 12 Status....................................................................................44 The Prevalence of Vitamin B 12 Deficiency.............................................................45 vii Vitamin B 12 and Hearing Loss ................................................................................46 Purpose, Specific Aims, Hypotheses, and General Approach ................................54 Figure 2.1.................................................................................................................11 Figure 2.2.................................................................................................................23 Table 2.1..................................................................................................................47 References ...............................................................................................................56 3 PREVALENCE OF HEARING IMPAIRMENT IN OLDER ADULTS IN THE OLDER AMERICANS ACT NUTRITION PROGRAMS ....................................67 Abstract ...................................................................................................................68 Introduction .............................................................................................................69 Methods...................................................................................................................70 Results .....................................................................................................................73 Discussion ...............................................................................................................74 References ...............................................................................................................77 Tables ......................................................................................................................80 4 HEARING IMPAIRMENT AND
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