Happiness and the Heart: an Investigation Into the Mechanisms Linking Psychological Well-Being, Work Stress and Cardiovascular Disease
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Happiness and the heart: an investigation into the mechanisms linking psychological well-being, work stress and cardiovascular disease Sophie Katharine Bostock Thesis submitted for the award of PhD Health Psychology, UCL Funded by the British Heart Foundation I, Sophie Bostock, confirm that the work presented in this thesis is my own. Where information has been derived from other sources, I confirm that this has been indicated in the thesis. 2 ‘He made her melancholy, sad, and heavy; And so she died: had she been light, like you, Of such a merry, nimble, stirring spirit, She might ha' been a grandam ere she died: And so may you; for a light heart lives long.’ Love’s Labour’s Lost (Act V, Scene II) William Shakespeare, first published 1598 3 Abstract Prospective studies have reported that positive psychological well-being is associated with a reduced risk of cardiovascular disease. Direct psychobiological processes have been implicated in this association. It is unclear to what extent well-being predicts health outcomes independently of chronic stressors, such as job strain. This thesis explores associations between well-being, job strain and outcomes relevant to cardiovascular disease in four empirical studies. Two biomarkers are investigated: cortisol, a neuroendocrine marker, and blood pressure. In study one, higher positive emotions over one week predicted lower reported stress during a standardised laboratory mental stress task, lower cortisol responses and faster blood pressure recovery. In study two, cross-sectional analyses of employee surveys indicated that low positive affect could mediate associations between job strain and fatigue, but reverse associations could not be discounted. Study three showed that job strain predicted heightened evening cortisol and a flatter diurnal rhythm in shift workers. Positive affect was not associated with cortisol. The hypothesis emerged that intervening to increase well-being might reduce perceived job strain and associated physiological activation. Study four tested this hypothesis in healthy workers using a mindfulness meditation smartphone application to promote well-being. The intervention was associated with increased well-being, reduced job strain and a trend for lower blood pressure after eight weeks. Decreased negative affect, not positive affect, predicted blood pressure declines. Changes in hair cortisol concentration were not associated with the intervention or psychological outcomes. Well-being appears to predict favourable cognitive appraisals of the work environment. Frequent positive emotions may reduce autonomic activation directly or via a reduction in negative emotion. Intervention findings suggested that self-guided mindfulness meditation practice enhanced well-being in the short term but effects on blood pressure and cortisol were inconclusive. Further research to examine longer term effects on psychological and biological outcomes is warranted to determine whether mindfulness-based therapies could play a role in cardiovascular disease prevention. 4 Table of Contents ABSTRACT ..................................................................................................................................... 4 ACKNOWLEDGEMENTS ....................................................................................................................11 INTRODUCTION ..................................................................................................................................12 CHAPTER 1 POSITIVE PSYCHOLOGICAL WELL-BEING AND THE RISK OF CARDIOVASCULAR DISEASE............................................................................16 1.1 Cardiovascular disease and psychosocial risk factors .......................................16 1.1.1 The burden of cardiovascular disease....................................................................................16 1.1.2 Psychosocial factors influence cardiovascular outcomes..............................................17 1.2 Defining and measuring subjective well-being.....................................................20 1.2.1 The life evaluation approach, a cognitive assessment ....................................................20 1.2.2 Hedonic well-being, the experience of pleasure................................................................21 1.2.3 Eudemonic well-being, positive mental functioning........................................................26 1.2.4 Towards a consensus: well-being as a multidimensional construct .......................27 1.3 Determinants, correlates and consequences of subjective well-being........30 1.4 Positive psychological well-being and cardiovascular outcomes..................39 1.4.1 CVD risk within in healthy populations.................................................................................41 1.4.2 CVD outcomes within patient populations...........................................................................48 1.4.3 Summary and limitations of the evidence from prospective studies.......................51 CHAPTER 2 PSYCHOBIOLOGICAL MECHANISMS LINKING WELL-BEING AND CARDIOVASCULAR DISEASE PROCESSES....................................................54 2.1 Psychosocial influences on biological processes implicated in CVD.............54 2.1.1 An overview of the stress response system.........................................................................54 2.1.2 How might well-being exert protective biological effects?...........................................57 2.2 Studies investigating the biological effects of well-being .................................59 2.2.1 Methods for investigating psychobiological mechanisms.............................................59 2.2.2 Cardiovascular function and positive psychological well-being ................................61 2.2.3 Salivary cortisol and well-being................................................................................................70 2.2.4 Subjective well-being and other biomarkers ......................................................................82 2.2.5 Summary of psychobiological studies and implications for this thesis...................85 CHAPTER 3 POSITIVE EMOTIONAL STYLE AND SUBJECTIVE, CARDIOVASCULAR AND CORTISOL RESPONSES TO ACUTE LABORATORY STRESS..........88 3.1 Introduction.......................................................................................................................88 3.1.1 Hypotheses .........................................................................................................................................90 3.1.2 Methods................................................................................................................................................90 3.2 Results..................................................................................................................................94 3.2.1 Hypothesis 1: Higher PES will be associated with lower subjective stress...........95 3.2.2 Hypothesis 2: Higher PES will be associated with rapid BP recovery .....................96 3.2.3 Hypothesis 3: PES will be associated with faster cortisol recovery..........................98 3.3 Discussion ...........................................................................................................................99 5 CHAPTER 4 CHRONIC WORK STRESS, HEART DISEASE & WELL-BEING .............. 103 4.1 Psychosocial work stress as a risk factor for heart disease ..........................103 4.1.1 Defining and measuring psychosocial work stress ....................................................... 104 4.1.2 Evidence linking psychosocial work stress to heart disease..................................... 108 4.1.3 Evaluating the evidence: does work stress cause heart disease? ........................... 111 4.2 Mechanisms linking job strain and heart disease.............................................113 4.2.1 Job strain and blood pressure................................................................................................. 118 4.2.2 Job strain and salivary cortisol............................................................................................... 121 4.3 Potential associations between work stress, positive affect & CVD...........133 CHAPTER 5 CROSS-SECTIONAL ASSOCIATIONS BETWEEN JOB STRAIN, POSITIVE AFFECT AND FATIGUE IN AIRLINE PILOTS............................................. 139 5.1 Introduction....................................................................................................................139 5.1.1 Hypotheses ...................................................................................................................................... 144 5.2 Methods ............................................................................................................................144 5.3 Results...............................................................................................................................149 5.3.1 Hypothesis 1: Job strain will be inversely associated with positive affect ........ 154 5.3.2 Hypothesis 2: PA & NA will mediate job strain to health associations................ 155 5.3.3 Hypothesis 3: PA as a moderator of the strain to health outcome association. 158 5.4 Conclusions......................................................................................................................159 CHAPTER 6 JOB STRAIN, POSITIVE AFFECT AND THE DIURNAL CORTISOL RHYTHM ON EARLY SHIFTS, LATE SHIFTS AND REST DAYS IN MALE PILOTS................................................................................................................