title: Socioeconomic inequalities in multimorbidity: an epidemiological and microsimulation study
Creators: name: Head, Anna
Publisher: name: University of Liverpool Repository
Year: 2024

description: Background: The increasing burden of multimorbidity – broadly defined as the coexistence of multiple chronic conditions within an individual – and its socioeconomic gradient, pose unique challenges to the provision and structure of health care. However, little research or policy focus has been placed on how to best prevent the development of multimorbidity in future generations.

Objectives: This thesis aims to explore the epidemiology of multimorbidity within the English primary care population, with particular focus on socioeconomic inequalities in the accumulation of multiple chronic conditions, and the potential for prevention strategies to equitably and effectively reduce the future burden of multimorbidity. 

Methods: Throughout the thesis, I use primary care electronic health records from a random sample of 1 million individuals in the Clinical Practice Research Datalink Aurum database registered at participating general practices within England between 1 January 2004, and 31 December 2019, linked to the 2015 English Index of Multiple Deprivation, an area-level measure of socioeconomic deprivation. I use two measures of multimorbidity: basic multimorbidity, comprising two or more chronic conditions; and complex multimorbidity, comprising at least three chronic conditions affecting at least three body systems. Chapter 6 presents a descriptive study of socioeconomic inequalities in multimorbidity incidence and prevalence over time. Chapters 7 and 8 summarise the development and validation of a dynamic stochastic microsimulation model of the accumulation of multimorbidity. Chapter 9 presents the simulation results of five theory-based policy approaches for improving population health and reducing inequalities in multimorbidity.

Results: The burden of multimorbidity in England increased substantially between 2004-2019: basic multimorbidity prevalence climbed from 30.8% to 52.8%, and complex multimorbidity doubled. There were persistent inequalities throughout the 16 years, especially in working-age adults and in those with complex multimorbidity. The microsimulation model results suggest that should these patterns continue, the prevalence of both basic and complex multimorbidity would continue to rise substantially from 2019 to 2049, with an increase of two thirds in the projected number of adults living with at least two chronic conditions from 16.2 million in 2019 to 27.4 million in 2049. 

Results from the theoretical scenarios for improving health and reducing health inequalities suggest that gains in levelling health inequalities could prevent/postpone multimorbidity cases and reduce health inequalities in the working age population. A proportionate universalism approach is likely to be the most effective option, whilst removing all socioeconomic inequalities would be the most equitable approach. In all scenarios, the projected reductions in both overall cases of multimorbidity and inequalities are concentrated in the working-age population. However, even then, the absolute numbers of those living with multimorbidity will likely continue to rise.

Conclusions: Inequalities in the burden of multimorbidity are greatest among the working-age population, in particular adults aged 40-60. Whilst substantial improvements in population health and decreases in health inequality, such as through a proportionate universalism approach, have the potential to postpone substantial numbers of multimorbidity cases, the multimorbidity burden will likely continue to rise over the coming decades, generating major challenges for future health and social services.