title: Exploration of the comorbidity of chronic pain, cardiometabolic disease and depression
Creators: name: Wu, Simin
Publisher: name: University of Glasgow
Year: 2023

description: Background and aims: Comorbidity is usually defined as the presence of one or more long-term conditions (LTCs) co-occurring with an index condition, while it can also be used to refer to a particular combination of multiple LTCs. In this thesis, the focus was on the comorbidity of chronic pain, cardiometabolic disease and depression. Chronic pain commonly co-occurs with other long-term conditions, particularly cardiometabolic disease and depression. Yet little is known about this comorbidity and its implications. This thesis aims to identify the existing knowledge of the comorbidity of chronic pain, cardiometabolic disease and depression; to examine the prevalence of the comorbidity in UK Biobank and investigate the sociodemographic and lifestyle factors associated with the comorbidity; to examine the effect of the comorbidity on health outcomes, and to describe the lived experience and insight of people living with this comorbidity. Methods: This was a multimethod study with four phases of research. 1) A narrative systematic review and synthesis of current literature relating to the comorbidity of chronic pain, cardiometabolic disease and depression. 2) A cross-sectional study of UK Biobank, a large dataset of over 500,000 adults aged 38-73 in the UK, in which the prevalence of the comorbidity was examined. Logistic regression was used to analyse associations between sociodemographic and lifestyle factors and the comorbidity, and the relationship between the three conditions. 3) An observational study of baseline data linked with routine health data, including hospital admission and mortality using UK Biobank. Incidence of death and Major Adverse Cardiovascular Events (MACE) in participants with and without the comorbidity were examined in the total study sample (N = 500,313). Survival analysis of a subsample (N = 128,066) was used to analyse the effect of the comorbidity on mortality and MACE, presented using hazard ratios (HR) with 95% confidence interval (CI). 4) A qualitative study involving secondary analysis of ten interviews from participants with the comorbidity. Thematic analysis was conducted to explore the everyday experience of living with the comorbidity alongside the participants' insights into the comorbidity and interacting with health care professionals. Results: Phase 1) The systematic review identified 15 relevant publications (13 studies). one study showed that chronic pain, angina, and depression co-occurred in 1.8% of the general population study sample. Key evidence gaps were identified regarding the prevalence, health effects and patient experience of the comorbidity. Phase 2) Among 500,313 eligible UK Biobank participants, 8,640 (1.73%) had the comorbidity, which was associated with being aged 45 years and older (particularly aged 55-59 years), being female, being from an ethnic group other than white, living in more deprived areas, current or past smoking, being overweight or obese as classified by Body Mass Index (BMI). While drinking alcohol (all categories compared to non-drinkers) and doing any physical activity were associated with a lower risk of the comorbidity. Phase 3) In the sub-sample (N = 128,066), participants with only the three conditions of interest had an increased risk of death presented (HR 2.10, 95% CI: 1.84, 2.41) and MACE (HR 2.13, 95% CI: 1.79, 2.52) compared with healthy participants after adjusting for covariates of sociodemographic and lifestyle factors. Phase 4) Chronic pain was described by the participants as the condition that has the most impact on their daily lives. Some participants considered chronic pain as a complication of their cardiometabolic disease. Others felt that depression was a result of their pain due to the impact it had on their life, particularly in terms of their independence, which has been considered in terms of biographical disruption. Nevertheless, participants felt that considering the combined conditions collectively was more important than focusing on the condition with the most impact. The importance of holism was emphasised, and participants reported a desire for health services to be holistic. Conclusion: Findings from each phase were integrated to address the overall research aim. There is a lack of existing literature on the comorbidity of chronic pain, cardiometabolic disease and depression, this combination of conditions was prevalent, associated with adverse health outcomes, and impacted the everyday lives of people. This thesis has important implications for health service provision suggesting a holistic approach to managing people with the comorbidity and has implications for wider multimorbidity research in general.