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CHAPTER 1 INTRODUCTION 1.1 Rationale and justification of the study Oral diseases, such as dental caries and periodontal diseases are most common chronic infectious diseases. Most caries and periodontal diseases are preventable, as recommended by resolution WHA 53.17 of the Fiftythird World Health Assembly in 2000 (1). However, the consequences of oral diseases are not only affected to oral cavity, but also to other systemic diseases such as diabetes, cardiovascular diseases, or respiratory diseases, preterm and low birth weight (2). There are several bacterial strains in normal flora of the oral cavity. Most of them are pathogens. Bacteria exist mainly inside the dental plaque and dental calculus and on the surface of soft tissue. Dental plaque was formed from mixture of food, saliva and other organic compounds inside oral cavity and it is the main cause of oral
WHAT EXPLAINS THE ASSOCIATION BETWEEN SOCIOECONOMIC STATUS AND DEPRESSION AMONG VIETNAMESE ADULTS? Vuong Diem Khanh Doan Doctor of Medicine (Hue University of Medicine and Pharmacy) Master in Public Health Methodology (Universite Libre de Bruxelles) Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy School of Public Health and Institute of Health and Biomedical Innovation Queensland University of Technology April, 2011 i What explains the association between socioeconomic status and depression among Vietnamese adults? Keywords Chronic stress, cross-sectional survey, depression, life time trauma, mastery, mediating effect, prevalence, psychological resources, recent life events, self esteem, social support, socioeconomic status, Vietnamese adults. ii What explains the association between socioeconomic status and depression among Vietnamese adults? Abstract Background Depression is a major public health problem worldwide and is currently ranked second to heart disease for years lost due to disability. For many decades, international research has found that depressive symptoms occur more frequently among low socioeconomic (SES) individuals than their more-advantaged peers. However, the reasons as to why those of low socioeconomic groups suffer more depressive symptoms are not well understood. Studies investigating the prevalence of depression and its association with SES emanate largely from developed countries, with little research among developing countries. In particular, there is a serious dearth of research on depression and no investigation of its association with SES in Vietnam. The aims of the research presented in this Thesis are to: estimate the prevalence of depressive symptoms among Vietnamese adults, examine the nature and extent of the association between SES and depression and to elucidate causal pathways linking SES to depressive symptoms Methods The research was conducted between September 2008 and November 2009 in Hue city in central Vietnam and used a combination of qualitative (in-depth interviews) and quantitative (survey) data collection methods. The qualitative study contributed to the development of the theoretical model and to the refinement of culturally-appropriate data collection instruments for the quantitative study. The main survey comprised a cross-sectional population–based survey with randomised cluster sampling. A sample of 1976 respondents aged between 25-55 years from ten randomly-selected residential zones (quarters) of Hue city completed the questionnaire (response rate 95.5%). iii What explains the association between socioeconomic status and depression among Vietnamese adults? Measures SES was classified using three indicators: education, occupation and income. The Center for Epidemiologic Studies-Depression (CES-D) scale was used to measure depressive symptoms (range0-51, mean=11.0, SD=8.5). Three cut-off points for the CES-D scores were applied: ‘at risk for clinical depression’ (16 or above), ‘depressive symptoms’ (above 21) and ‘depression’ (above 25). Six psychosocial indicators: life time trauma, chronic stress, recent life events, social support, self esteem, and mastery were hypothesized to mediate the association between SES and depressive symptoms. Analyses The prevalence of depressive symptoms were analysed using bivariate analyses. The multivariable analytic phase comprised of ordinary least squares regression, in accordance with Baron and Kenny’s three-step framework for mediation modeling. All analyses were adjusted for a range of confounders, including age, marital status, smoking, drinking and chronic diseases and the mediation models were stratified by gender. Results Among these Vietnamese adults, 24.3% were at or above the cut-off for being ‘at risk for clinical depression’, 11.9% were classified as having depressive symptoms and 6.8% were categorised as having depression. SES was inversely related to depressive symptoms: the least educated those with low occupational status or with the lowest incomes reported more depressive symptoms. Socioeconomically- disadvantaged individuals were more likely to report experiencing stress (life time trauma, chronic stress or recent life events), perceived less social support and reported fewer personal resources (self esteem and mastery) than their more- advantaged counterparts. These psychosocial resources were all significantly associated with depressive symptoms independent of SES. Each psychosocial factor showed a significant mediating effect on the association between SES and depressive iv What explains the association between socioeconomic status and depression among Vietnamese adults? symptoms. This was found for all measures of SES, and for males and females. In particular, personal resources (mastery, self esteem) and chronic stress accounted for a substantial proportion of the variation in depressive symptoms between socioeconomic groups. Social support and recent life events contributed modestly to socioeconomic differences in depressive symptoms, whereas lifetime trauma contributed the least to these inequalities. Conclusion This is the first known study in Vietnam or any developing country to systematically examine the extent to which psychosocial factors mediate the relationship between SES and depression. The study contributes new evidence regarding the burden of depression in Vietnam. The findings have practical relevance for advocacy, for mental health promotion and health-care services, and point to the need for programs that focus on building a sense of personal mastery and self esteem. More broadly, the work presented in this Thesis contributes to the international scientific literature on the social determinants of depression. v What explains the association between socioeconomic status and depression among Vietnamese adults? Table of Contents Keywords… i Abstract…… ii Table of Contents v List of Figures ix List of Tables x List of Abbreviations xiv Statement of Original Authorship xvii Contributions to Thesis xviii Ethical Clearance xix Acknowledgments xx CHAPTER 1:INTRODUCTION 1 1.0 Background 1 1.1 Research aim and questions 5 1.1.1 Research aim 5 1.1.2 Research questions 5 1.2 Outline of this Thesis 5 CHAPTER 2:LITERATURE REVIEW 7 2.0 Introduction 7 2.1 Definition of depression 7 2.2 Psycho-behavioural theories of depression 8 2.2.1 Learned helplessness 9 2.2.2 Cognitive constructions of self and reality 9 2.2.3 Response Contingent Positive Reinforcement Theory 10 2.2.4 Psychoanalytic theories 10 2.3 Rating scales for measuring depression 11 2.3.1 Classification 11 2.3.2 Overview of currently-used depression rating scales 14 2.4 International prevalence of depression 19 2.5 The relationship between socioeconomic status and depression 24 2.5.1 Introduction 24 2.5.2 Conceptualising SES 24 2.5.3 Education and depression 26 2.5.4 Occupation and depression 27 vi What explains the association between socioeconomic status and depression among Vietnamese adults? 2.5.5 Income and depression 27 2.6 Conceptualising the association between SES, depression and health 30 2.7 The association between stress and depression 33 2.7.1 Conceptualising stress 33 2.7.2 The association between stress and depression 34 2.8 The association between social support and depression 36 2.8.1 ConceptualiSing social support 36 2.8.2 The association between Social support and depression 38 2.9 The association between psychological resources and depression 40 2.9.1 Conceptualising self esteem 40 2.9.2 The association between self esteem and depression 41 2.9.3 Conceptualising mastery 42 2.9.4 The association between mastery and depression 44 2.10 The association between SES and stress, social support and psychological resources……………… 45 2.10.1 Association between SES and stress 45 2.10.2 Association between SES and social support 47 2.10.3 Association between SES and psychological resources 49 2.11 Research on depression in Vietnam 53 2.12 Hypotheses and conceptual model of the study 55 2.11.1 Hypotheses 55 2.11.2 Conceptual model 56 2.13 Chapter summary 57 CHAPTER 3:RESEARCH METHODS 59 3.0 Introduction 59 3.1 Timeline 59 3.2 Geographic location and scope 59 3.3 Research design……………………………………………………………….61 3.4 Phase 1: Pilot study 62 3. 4.1 Exploratory qualitative research 62 3. 4.2 Pilot study of the quantitative survey 67 3.5 Phase 2: Main survey 75 3.5.1 Sample size 75 3.5.2 Sample selection 76 3.5.3 Training of data collectors 77 3.5.4 Preparing for data collection 77 3.5.5 Data collection 77 3.5.6 Data management 78 3.5.7 Data screening 79 3.5.8 Measures 80 3.5.9 Data analyses 105 3.6 Summary 113 vii What explains the association between socioeconomic status and depression among Vietnamese adults? CHAPTER 4:RESULTS 115 4.0 Introduction 115 4.1 Prevalence of depressive symptoms and depression 116 4.1.1 Overall prevalence of depression 116 4.1.2 Sociodemographic factors and the prevalence of depression 116 4.2 Descriptive (bivariate) analyses of the association between SES, depression and each of the mediators 122 4.2.1 Socioeconomic status and depression scores (CES-D) 122 4.2.2 Socioeconomic status and lifetime trauma 123 4.2.3 Socioeconomic status and chronic stress 124 4.2.4 Socioeconomic status and recent life events 125 4.2.5 Socioeconomic status and social support 126 4.2.6 Socioeconomic status and self esteem 127 4.2.7 Socioeconomic status and mastery 128 4.3 Mediation analyses: The causal steps approach - three steps in Baron and Kenny’s framework 129 4.3.1 Step 1: The Total effects of SES on depression 129 4.3.2 Step 2: Multiple regression of potential mediators on SES 133 4.3.3 Step 3: Multiple regression of CES-D score on potential mediators - controlling for the effect of SES 146 4.4 Estimating the size and significance of the indirect or mediated effects 150 4.4.1 The mediated effect of lifetime trauma on SES and depression 151 4.4.2 The mediated effect of chronic stress on SES and depression 155 4.4.3 The mediation effect of recent life events on SES and depression 158 4.4.4 The mediation effects of social support on SES and depression 162 4.4.5 The indirect effects or mediated effect of self esteem on SES and depression 166 4.4.6 The indirect effect or mediated effect of mastery on SES and depression 169 4.5 Percentage mediation of total effects of SES on CES-D: summary 172 4.6 Summary 184 CHAPTER 5:DISCUSSION 187 5.0 Introduction 187 5.1 Prevalence of depressive symptoms and depression 187 5.1.1 Prevalence of being ‘at risk for clinical depression’ 188 (CES-D≥ 16) 188 5.1.2 Prevalence of depressive symptoms (CES-D > 21) and depression (CES-D > 25) 190 5.1.3 Gender and depression……………………………………………… 192 5.1.4 Age and depression ………………………………………………… 193 5.1.5 SES and the prevalence of depression……………………………… 195 5.2 Psychosocial mediators of the SES-depression relationship 197 viii What explains the association between socioeconomic status and depression among Vietnamese adults? 5.2.1 Association between SES and levels of depressive symptoms 197 5.2.2 The mediating role of stress 198 5.2.3 The mediating role of social support 203 5.2.4 The mediating role of self esteem 206 5.2.5 The mediating role of mastery 208 5.2.6 Comparing mediating effects of different psychosocial factors 213 5.2.7 Gender difference in mediating effects 219 5.3 Study strengths, limitations and implications for further research 219 5.3.1 Strengths 219 5.3.2 Study limitations and implications for further research 221 5.4 Implications for mental health policy in Vietnam 224 5.5 Conclusion 232 BIBLIOGRAPHY 234 APPENDIX A: GUIDELINES FOR EXPLORATORY QUALITATIVE RESEARCH ……………………………………………………………………….267 APPENDIX B: SURVEY QUESTIONNAIRE 271 APPENDIX C: RESULTS OF EXPLORATORY QUALITATIVE RESEARCH 293 APPENDIX D: RESULTS OF PILOT QUANTITATIVE RESEARCH 303 APPENDIX E: CONFIRMATORY FACTOR ANALYSIS 324 APPENDIX F: BIVARIATE RELATIONSHIPS BETWEEN EACH SES INDICATOR AND THE CONTROL VARIABLES (AGE, MARITAL STATUS, SMOKING, DRINKING AND CHRONIC DISEASES) 327 APPENDIX G: VIETNAM MAP AND LOCATION OF STUDY SITE 333 APPENDIX H: PICTURES OF HOUSEHOLD BOOKLET AND TRANING DATA COLLECTORS 335 [...]... symptoms in a community in the central region of Vietnam and to elucidate the causal pathways between SES and depression in this community 1.1.2 RESEARCH QUESTIONS 1 What is the prevalence of depression among adults in this community in central Vietnam? 2 What is the nature and extent of the association between SES and depression among Vietnamese adults? Is the socioeconomic- depression gradient in Vietnam... for measuring depression The fourth section includes estimates of the prevalence of depression in a range of countries The association between SES and depression, and the connection between SES, depression and health are examined in the following two sections The relationship between psychosocial resources and depression and the association between SES and psychosocial resources are then examined Basic... SES Socioeconomic status SAM Sympathetic adrenal–medullary system SD Standard deviation SWAN Study of Women’s Health Across the Nation VBSP Vietnam Bank for Social Policies VO Village Organisation WHO World Health Organization Zung SDC Zung Self-Rating Depression Scale xvi What explains the association between socioeconomic status and depression among Vietnamese adults? Contributions to Thesis The. .. between socioeconomic status and depression among Vietnamese adults? Ethical Clearance The study presented in this thesis was awarded ethical clearance by the University Human Research Ethics Committee (UHREC) at the Queensland University of Technology, Australia (ethic approval number 0800000642) and the Research Ethics Committee of Hue University of Medicine and Pharmacy, Vietnam What explains the association. .. understanding the likely relevance of the theories for examining the causal pathway linking SES to depression As such, this section will first describe the main theories that have been advanced in the literature, followed with the Researcher’s view on the explanation of the association between SES and depression according to the relevant theories 8 Chapter 2: Literature review 2.2.1 LEARNED HELPLESSNESS The. .. from other cultures? 3 What factors mediate the relationship between SES and depression among Vietnamese adults? In particular, how much of the relationship between SES and depression can be explained by socioeconomic differences in psychosocial resources (life time trauma, chronic stress, recent life events, social support, self esteem and mastery)? 1.2 OUTLINE OF THIS THESIS CHAPTER 1 sets the background... chapter then includes a review of estimates of the prevalence of depression published internationally The association between SES and depression, psychosocial resources and depression, SES and psychosocial resources are then explored in detail Key information on the small body of research on depression in Vietnam is also presented Based on the literature review, this chapter ends by proposing the hypotheses... collection and the analytic strategies CHAPTER 4 describes the overall prevalence of depressive symptoms and depression, and bivariate association of these with sociodemographic factors Bivariate associations between SES, depression and each psychosocial mediator are then examined The next section provides a detailed mediation analysis, following the three steps in Baron and Kenny’s framework Estimates of the. .. openness in responding to the study’s questionnaire: their contributions have helped produce a valuable and useful piece of research that will hopefully benefit all residents of Hue and Vietnam I am very much thankful to Atlantic Philanthropies for their generous provision of funds for this study What explains the association between socioeconomic status and depression among Vietnamese adults? xx I am forever... sample…………………………… 100 Table 3.16 Smoking status distribution of the sample………………………… 100 Table 3.17 Alcohol consumption distribution of the sample…………………… 101 x What explains the association between socioeconomic status and depression among Vietnamese adults? Table 3.18 Chronic diseases distribution of the sample………………………… 102 Table 3.19 Descriptive statistics of the CES-D scale…………………………… 103 Table 3.20 . Education and depression 26 2.5.4 Occupation and depression 27 vi What explains the association between socioeconomic status and depression among Vietnamese adults? 2.5.5 Income and depression. social support, socioeconomic status, Vietnamese adults. ii What explains the association between socioeconomic status and depression among Vietnamese adults? Abstract Background Depression. significant mediating effect on the association between SES and depressive iv What explains the association between socioeconomic status and depression among Vietnamese adults? symptoms. This was