UNIVERSITY OF CALIFORNIA Los Angeles Relationship between Psychosocial Stress and Allostatic Load: Findings from the MIDUS study A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Epidemiology by Stephanie Rummans Reading 2015 © Copyright by Stephanie Rummans Reading 2015 ABSTRACT OF THE DISSERTATION Relationship between Psychosocial Stress and Allostatic Load: Findings from the MIDUS study by Stephanie Rummans Reading Doctor of Philosophy in Epidemiology University of California, Los Angeles, 2015 Professor Teresa E. Seeman, Chair Scientific evidence continues to accumulate that relates the experience of stress with overall poor health. However, defining what is meant by the term ‘stress’, in-order to examine its association with the experience adverse health, has been a difficult task for medical researchers. In the present investigation, using linear mixed effect regression analyses, we were interested in evaluating how the experience of psychosocial stress was related to one conceptualization of ‘stress’ as it impacts the human body, allostatic load. Allostatic load, proposed as ‘the cost of chronic exposure to fluctuating or heightened neural or neuroendocrine response resulting from repeated or chronic environmental challenge that an individual reacts to as being particularly stressful’ has been identified in the medical literature as mechanism that is associated with numerous negative health events, especially with regards to overall worse cardiovascular and immune system health. Our aim was to identify the extent to which a cumulative measure of ii psychosocial stress was related to allostatic load, as well as, identify the relative contributions of eleven specific dimensions of stress to that relationship. We also evaluated whether and how these relationships were moderated by sociodemographic, health behavior and psychosocial resource characteristics, to better understand how psychosocial stress was related to allostatic load across various sub-populations. Data for the analyses were obtained from the Midlife Development in the United States (MIDUS) study, a national, longitudinal investigation with a purpose to investigate the role of the behavioral, psychological and social factors that account for the age related variations in health and well-being across a national sample of Americans. As presented within the written dissertation, further information is provided for readers as an overall introduction to the dissertation (Chapter 1), additional details regarding our proposed aims (Chapter 2), the background and significance for our line of inquiry (Chapter 3), the analytical methods that were implemented for the purpose of this investigation (Chapter 4), the results and findings from our analyses (Chapter 5), a discussion of the results and findings (Chapter 6) and then a highlight of the main study limitations (Chapter 7) along with our overall study conclusions (Chapter 8). iii This dissertation of Stephanie Rummans Reading is approved. Arun S. Karlamangla Beate R. Ritz Dallas T. Swendeman Teresa E. Seeman, Committee Chair University of California, Los Angeles 2015 iv Table of Contents CHAPTER I. Introduction …………………………...……………………...………………………...... p. 1 CHAPTER II. Specific Aims …………………...……………………….……………………………… p. 4 AIM 1 …………………………………………………….……….…………………….….….. p. 5 Hypothesis 1 ……………………………………….………………….…......……….. p. 5 Hypothesis 2 …………………………………………….………………….………… p. 5 AIM 2 …………………………………………………….……….………………….…........... p. 5 Hypothesis 3 …………………………………………….………………….…............ p. 5 AIM 3: PART 1 ……………………………………………….….………………….….…....... p. 6 Hypothesis 4 …………………………………………….………………….…............ p. 6 AIM 3: PART 2 ……………………………………………….….………………….….…....... p. 7 Hypothesis 5 …………………………………………….………………….…............ p. 7 AIM 4: PART 1 ……………………………………………….….………………….….…....... p. 7 Hypothesis 6 …………………………………………….………………….…............ p. 8 AIM 4: PART 2 ……………………………………………….….………………….….…....... p. 8 Hypothesis 7 …………………………………………….………………….…............ p. 8 CHAPTER III. Background and Significance …………….....………….……………………….…....... p. 9 3.1 Stress ……………………………………………………………………………................. p. 9 3.2 Allostasis and Allostatic Load ……………………………………………………….......... p. 11 3.3 Psychosocial Stress ……………………………………………………………………....... p. 17 CHAPTER IV. Methods …………….....……………….....………….……………………….…........... p. 20 4.1 Overview of the Midlife Development in the United States (MIDUS) Study ……….......... p. 20 4.2 Study Participants and Sampling …………………….………………………………......... p. 22 MIDUS I Main Study …………………....…………………………………...…......... p. 22 MIDUS II Resurvey Study ………..……………………………………….…............. p. 24 MIDUS II Biomarker Study ………………………..………………………….. ......... p. 27 4.3 Data Collection …………………………………………………………..……..…….......... p. 28 MIDUS II Resurvey Study …………………………………..…………….……......... p. 28 MIDUS II Biomarker Study ………………………..…………………….….….......... p. 31 4.4 Dependent Variable: Allostatic Load …………………………………………..…….......... p. 32 4.5 Independent Variables: Psychosocial Stress Domains ……………………………….......... p. 37 Psychological Work Stress ………………………………………..........…………...... p. 37 Physical Work Stress ……………………………………...........................………...... p. 39 Work-Family Spillover Stress ……………………………………………………....... p. 41 Perceived Inequality ……………………………………………...........…………....... p. 42 v Relationship Stress ……………………………………………...……………..…........ p. 44 Neighborhood Stress ………………………………………….....………………......... p. 46 Discrimination ………………………………………………........................……....... p. 47 Current Financial Stress …………………………………………………………...... p. 50 Past Year Problems in the Immediate Family ……………………..……………......... p. 51 Stressful Life Experiences …………………………………………..……………....... p. 52 Early Life Stress ……………………………………………………..……..……........ p. 54 Missing Data Imputation …………………………………………...……………........ p. 56 Summary Index Measure of Overall Stress ………………………………………....... p. 56 Imputation Flags …………………………………………………….......……..…....... p. 57 4.6 Analysis Covariates: Sociodemographic Characteristics …………………………….......... p. 57 Age and Gender …………………………………………………............………......... p. 58 Race/Ethnicity ………………………………………………..........…………..…....... p. 58 Income ……………………………………………………….....…..……..…….......... p. 60 Educational Attainment …………………………………………………………......... p. 61 Marital Status …………………………………………………………..……..…........ p. 62 4.7 Analysis Covariates: Health Behavior Characteristics ………………………………......... p. 64 Physical Activity …………………………………………………………..……......... p. 64 Smoking Status …………………………………………………………..……............ p. 66 Alcohol Use …………………………………………………………..……..…........... p. 67 4.8 Analysis Covariates: Psychosocial Resource Characteristics ………………………........... p. 67 Psychological Well-Being Scales ……………………………………………….......... p. 68 Coping Scales …………………………………………………………..……..…........ p. 71 Personality Trait Scales …………………………………………………………......... p. 73 4.9 Statistical Methods …………………………………………………………..……..…........ p. 75 Pre-Regression Analyses …………………………………………………………....... p. 75 Aims 1 and 2 …………………………………………………………..……..…......... p. 76 Aim 3 …………………………………………………………..……...............…........ p. 77 Aim 4 …………………………………………………………..……...............…........ p. 78 CHAPTER V. Results …………………………………………………………..……..…….................. p. 79 5.1 Descriptives …………………………………………………………..……..…….............. p. 79 5.2 Aims 1 and 2 ...............................……………...………….....………...................…........... p. 80 Analysis of Main Effects: Summary Index Measure of Overall Stress ….................... p. 80 Analysis of Main Effects: Component Psychosocial Stress Domains .…..................... p. 81 5.3 Aim 3 ...................………………............……………………………………..................... p. 82 Individual Moderation Models: Summary Index Measure of Overall Stress ............... p. 82 vi Simultaneous Moderation Models: Summary Index Measure of Overall Stress .......... p. 83 Select Moderation Models: Component Psychosocial Stress Domains ........................ p. 84 5.4 Aim 4 ....…………………….........……………...........................….…................................ p. 88 Individual Psychosocial Resource Moderation Models ................................................ p. 88 Simultaneous Psychosocial Resource Moderation Models ........................................... p. 88 Age Differences in Psychosocial Resource Moderation Models (Stratified Analyses) ....... p. 89 Gender Differences in Psychosocial Resource Moderation Models (Stratified Analyses) .. p. 89 Educational Differences in Psychosocial Resource Moderation Models (Stratified Analyses) p. 90 CHAPTER VI. Discussion ....................................................................................................................... p. 92 6.1 Aims 1 and 2 ...........................…………………………….....………..................…........... p. 92 6.2 Aim 3 ......................................………………………….....………...................…............... p. 94 Age .....................................………………………….....……….................…............. p. 94 Race/Ethnicity ......................................………………………….....………................ p. 97 Marital Status ......................................………………………….....……….................. p. 100 6.3 Aim 4 .....................................…………………………….....………...................…............ p. 102 Age Stratified Analyses ......................................………………………….....….......... p. 103 Gender Stratified