The health economics of obesity and bariatric surgery

\\(Background:\\) Obesity is not only a major health concern, it is an economic problem. The current rates of obesity (defined as body mass index (BMI) ‚Äöv¢‚Ä¢ 30 kg/m\\(^¬¨‚â§\\)) are epidemic and severe obesity (defined as BMI ‚Äöv¢‚Ä¢ 35 kg/m\\(^¬¨‚â§\\)) is increasing more rapidly than obesity. Treatments for overweight and obesity include dietary therapy, exercise/behavioural interventions, weight loss medications and bariatric surgery. Bariatric surgery is considered the most efficacious intervention for severe and resistant obesity. This PhD thesis titled 'The Health Economics of Obesity and Bariatric Surgery' is an important part of a comprehensive, mixed-methods and multi-disciplinary Australian National Health and Medical Research Council (NHMRC) partnership project regarding bariatric surgery as a treatment option for obesity, within the State of Tasmania (Australia), nationally, and internationally. Key health economic evidence gaps were initially identified in the development of the successful NHMRC partnership project grant proposal. \\(Aims:\\) As a health economist within the NHMRC partnership project team, the principal aims of my PhD research were to: provide critical baseline analyses of the key themes and evidence gaps regarding the health economic reporting of bariatric surgery, locally, nationally and internationally; address key evidence gaps regarding the physical and psychosocial domains of health-related quality of life from the time of waitlisting for bariatric surgery; establish the multi-attribute utility instrument that preferentially captures the physical and psychosocial health-related quality of life of people waiting for, or who have undergone bariatric surgery; use qualitative research methods to investigate bariatric surgery patients' experiences to identify and prioritise health economic impacts of bariatric surgery that are typically excluded from existing studies, or not provided with sufficient priority; and develop a strategic research alliance with our Tasmanian State Government project partner to investigate the resource use and costs of obesity and bariatric surgery to the Tasmanian public hospital system. \\(Methods:\\) This thesis adopted a mixed-methods approach within real-world policy settings, consistent with a call for health economists to implement mixed-methods and policy-relevant research that is embedded in, and derived from real-world policy settings. First, validated guidelines and methodologies were followed in the systematic selection and analyses of the published literature regarding the health economic evaluation of bariatric surgery. The findings of this comprehensive systematic review informed the methods of the remainder of the thesis (Chapter 2). Second, the vastly different EQ-5D-5L and AQoL-8D multi-attribute utility instruments were systematically selected to investigate health state utility valuations (both instruments) and individual and super dimension scores (AQoL-8D only) in two cohorts of bariatric surgery patients. Patients who had received bariatric surgery many years previously in the private healthcare system (cross-sectional - Chapter 3) and patients who were publicly waitlisted for their surgery for many years and then operated on as part of a government policy decision to reduce waiting lists (longitudinal - Chapters 4 and 5) were studied. Third, qualitative research methods were used to investigate bariatric surgery patients' 'lived' experiences to identify and prioritise health economic impacts of bariatric surgery that are typically excluded from existing studies (Chapters 6 and 7). Fourth, a strategic research alliance with the critical health and project partner was adopted to construct and analyse a Tasmanian public hospital resource use and cost database about publicly-waitlisted patients before and after their primary bariatric surgery and surgical sequelae (Chapter 8). \\(Thesis\\) \\(outline\\) \\(and\\) \\(summary\\) \\(of\\) \\(key\\) \\(results:\\) Chapter 1 presents a general introduction of the health and economic burden of the obesity epidemic and bariatric surgery as a treatment option, and health economic concepts pertinent to this thesis. Chapter 2 provides a published comprehensive systematic review of the health economic evaluation of bariatric surgery. Evidence gaps identified in the systematic review informed the direction of the subsequent PhD projects of this thesis, part of the work program for the NHMRC partnership project, and some of the future directions for research beyond this thesis. Among other things, this study found that only 13% of included studies adopted a broader societal perspective, the cost of complications and reoperations for bariatric surgery were not included in one-third of studies and when they were included conservative estimates were generally adopted, out-of-pocket costs were largely ignored, the EQ-5D suite of multi-attribute utility instruments was prevalent in the health economic evaluation of bariatric surgery, and that only one study investigated publicly waitlisted patients. The study's quality appraisalagainst the Consolidated Health Economic Evaluation Reporting Standards checklist found heterogeneous approaches, inconsistent quality and key evidence gaps in the health economic reporting of bariatric surgery. Chapters 3, 4 and 5 present the first integrated published suite of health-related quality of life studies for the bariatric surgery study population that systematically selected two markedly different multi-attribute utility instruments, namely the EQ-5D-5L (Chapter 2 established the EQ-5D-5L was the internationally prevalent instrument in the economic evaluation of bariatric surgery) and the AQoL-8D (based on psychometric principles and testing). Importantly, the two instruments were used and compared for two different cohorts of bariatric surgery patients. Chapter 3 provides the first head-to-head comparison of the EQ-5D-5L and AQoL-8D for a cross-sectional cohort of patients who had received bariatric surgery in the private healthcare sector many years previously (median (interquartile range) 5 (3-8) years). Chapter 3 found that psychosocial health was a key driver for the study population and that the AQoL-8D preferentially captured and assessed their psychosocial health. This study also explored the international dominance of the EQ-5D in the clinical and economic evaluation literature and the paper recommended that the choice of multi-attribute utility instrument should be influenced by the innate sensitivities of the instrument to the relevant domains of heath for the particular study population. Chapters 4 and 5 were the first studies to use the EQ-5D-5L and AQoL-8D for a unique cohort of long-term and severely obese publicly waitlisted patients who then received bariatric surgery due to a public policy decision to reduce waiting lists. Chapter 2 identified that only one health economic study investigated the impact of waiting for bariatric surgery. A key finding of these studies was that the preoperative AQoL-8D health state utility valuation for this increasingly prevalent subgroup of bariatric surgery patients was less than those of people with cancer or heart disease. Even 3 months, and then 1 year after bariatric surgery, long-term publicly waitlisted patients recorded significant and clinically meaningful health-related quality of life improvements. This result suggested that long-waiting patients should not be 'written-off' by healthcare decision makers: they can still realise significant improvements in health-related quality of life outcomes when ultimately treated, and this should be factored into patient prioritisation decisions. Chapters 4 and 5 also investigated the emerging literature regarding the predictive capabilities of multi-attribute utility instruments in patient-centred bariatric care. Chapters 6 and 7 present studies that harness the unique advantages of qualitative research methods to improve our practice in health economics. The inspiration for the method of these studies was partly directed by the systematic review (Chapter 2) that identified the limited scope of costs and consequences for most health economic evaluations of bariatric surgery. Additionally, there has been a call for health economists to effectively integrate combinations of qualitative and quantitative methods into their research toolkit to enrich their research methodologies and therefore improve their practice in health economic study design, data gathering and analysis, reporting and ultimately research translation. These studies listened to patients' stories and key themes were identified inductively through a dialogue between the qualitative focus group data and pre-existing economic theory (perspective; externalities; emotional capital; information asymmetry). Published Chapter 6 identified the concept of emotional capital as a 'potentiator' for human capital where participants described life-changing desires to be productive and participate in their communities postoperatively. Two-thirds of the focus group participants accessed private healthcare for bariatric surgery and some of these participants experienced substantial economic burden to do so. Chapter 7 presents a second health economics study that implemented qualitative research methods. The inspiration for this study was that a key market failure in healthcare is information asymmetry. However, in the information-age, bariatric surgery patients may be more empowered in their negotiated relationship with healthcare providers through demand-induced supply. This study found a divergence between the pre- and postoperative information drivers. Psychosocial or socio-emotional drivers informed the sources and types of information that were important to participants preoperatively. The study also found that information sources relevant to participants preoperatively (e.g. family and friends, and the I...