Exploring the relationship between eating disorders and quality of life : a symptom and community-based approach

Abstract

Although interest in quality of life in the field of eating disorders has steadily increased over the past two decades, there remained significant methodological limitations in the exploration of the relationship between eating disorders and quality of life. Foremost among these included the predominance of clinical samples, the narrow demographic of participant samples, the use of disease-specific versus generic measures of health-related quality of life, and the unidirectional nature of previous studies investigating the impact of eating disorders on quality of life. The objective of this thesis was to explore the relationships between eating disorders (and specific eating disorder features) and health-related quality of life using predominantly community and population-based data. The objective of the first study presented in chapter four was to conduct a psychometric comparison of a widely used generic measure of health-related quality of life (SF-12) and a widely used disease-specific measure of health-related quality of life (EDQOL). Chapter five aimed to assess the impairment in health-related quality of life and residual symptoms associated with having a history of anorexia nervosa. The aims of chapters six through to nine were to investigate the relationship between specific disordered eating and body image features with health-related quality of life. Chapter six investigated whether features usually associated with body dysmorphic disorder were associated with impaired health-related quality of life in people with eating disorders. Chapters seven and nine investigated demographic differences in the impairment in health-related quality of life associated with eating disorder features. Chapters eight and nine investigated temporal changes in the impairment in health-related quality of life associated with specific eating disorder features. Finally the objective of chapter ten was to investigate for the first time possible bidirectional relationships between eating disorder symptoms and health-related quality of life. Four datasets were used: 1.) a treatment sample of participants with anorexia nervosa (chapter four); 2.) a longitudinal community cohort of women followed over a period of nine years (chapters six and ten); 3.) a population sample of South Australia collected in 1998 (chapters eight and nine); and 4.) a population sample of South Australia collected in 2008 (chapters five, seven, eight, and nine). The Medical Outcome Studies Short Forms were used to collect data on health-related quality of life: the SF-12 in samples 1 and 2, and the SF-36 in samples 3 and 4. In addition the Eating Disorder Quality of Life instrument (EDQOL), a disease-specific measure of health-related quality of life was administered to sample 1. The assessment of eating disorder and body dysmorphic pathology varied across samples. The Eating Disorder Examination (EDE) interview was used in sample 1. The questionnaire versions of the EDE (EDE-Q) and the body dysmorphic disorder examination (BDDE-SR) were used in sample 2. Finally, samples 3 and 4 were asked specific questions modelled on the EDE interview regarding whether or not they had engaged in specific eating disorder behaviours at least weekly over the past three months or endorsed overvaluation of body weight/shape. Other measures of impairment and distress used included the Work and Social Adjustment Scale (WSAS) and a question on days out of role (DOR) in sample 1, and the Kessler Psychological Distress Scale (K-10) in sample 2. All samples were asked basic demographic questions. The statistical methods varied across studies and included correlational analysis, multiple linear regression, chi-square tests, logistic regression, analyses of variance, and structural equation modelling. The main findings from chapter four were that the EDQOL and SF-12 were both adequate as indicators of impairment, although the SF-12 converged more strongly with measures of functional impairment and was better able to predict later changes in eating disorder severity compared to the EDQOL. Chapter five found that a self-reported history of anorexia nervosa was associated with continued impairment in quality of life despite not meeting current criteria for diagnosis. Further, participants who reported a history of anorexia nervosa were also more likely to report ego-dystonic eating disorder features such as objective binge eating and most were currently overweight. Regarding specific eating disorder and body image features, chapter eight found that eating disorder symptoms (most strongly objective binge eating and overvaluation of weight or shape) were associated with impairment in health-related quality of life. Further, in chapter six symptoms commonly associated with body dysmorphic disorder (such as preoccupation, compulsive checking, reassurance-seeking, and camouflaging) were also found to be associated with additional distress and impairment in the health-related quality of life of participants with probable eating disorders. In regards to the sex differences explored in chapter seven, although women were more likely to report eating disorder symptoms, for the most part the impairment in health-related quality of life associated with these symptoms was similar between the men and women who reported them. Two exceptions however were that objective binge eating was associated with poorer mental health-related quality of life in men while overvaluation of weight and/or shape was associated with poorer health-related quality of life in women. The time trends in chapters eight and nine indicated that the prevalence of eating disorder symptoms had increased over the time period from 1998 to 2008. However while the impairment in health-related quality of life associated with symptoms remained stable in the overall population sample over this time, closer inspection demonstrated that impairment had increased in underserved and underrepresented demographic sectors, such as lower socioeconomic, regional-dwelling, and male participants. Finally, the findings in chapter ten provided evidence of a bidirectional relationship between eating disorder symptoms and health-related quality of life over time, and the longevity of this relationship was greater for physical as compared to mental health-related quality of life. The studies in this thesis taken together have enhanced the current knowledge regarding the relationship between eating disorders and health-related quality of life. In particular, confidence in the findings within this thesis is increased by the use of community and population-based samples, longitudinal and sequential cross-sectional datasets, and the inclusion of a broader demographic than has been typically seen in previous study samples. The implications of the findings include the recommendation to review criteria related to functional impairment and overvaluation of weight/shape in the diagnostic classification schemes of all eating disorders, and to investigate the efficacy of targeting broader body image symptoms (such as those traditionally associated with body dysmorphic disorder) and quality of life in treatment interventions for people with eating disorders.

Date of Award	2014
Original language	English