Obesity is a global public health threat and in the past 40 years, the prevalence of obesity worldwide has nearly tripled. High body mass index (BMI) accounted for 4 million deaths globally in 2015-2016, and it was estimated that 1.9 billion adults were overweight, of which 650 million were obese. If the increase in obesity prevalence continues as expected, by 2025 3.7 billion adults are projected to be overweight.
Obesity increases the risk of a number of diseases and conditions, such as cardiovascular disease (stroke, heart attack, etc.), cancers, mental health, among many others; this also increases the risk of premature death. Deaths due to cardiovascular disease has been decreasing, and considering people are living with obesity for a longer period of time, the risk of death from a wider range of conditions is increasing. Further, although obesity is known to lead to a wide range of conditions, few studies have compared the population disease of obesity across a comprehensive spectrum of its associated conditions. This impacts not only the quality of life of the individual, but also puts more pressure on health services.
This study aims to understand how the cause-of-death and diseases/conditions are changing in those who are overweight and obese in England. This research will provide vital information on the diversity and complexity of obesity-related disease and conditions to support those impacted by the health consequences of obesity but also public policy and interventions.
This study aims to advance our understanding of the heterogeneous and changing impact of overweight and obesity, through morbidity and cause-specific mortality, in UK adults.
This will be a dynamic cohort which will estimates the trends in obesity-related morbidity and mortality among overweight and obese adults. The primary exposures of interest will be BMIs which will use continuous BMI measurements to assess non-linear relationships between BMI and mortality/morbidity and categorised BMI using the WHO definitions. The categories will be defined as: normal weight (<25 kg /m2), overweight(BMI 25-29.9 kg/m2) and obesity is a BMI >30 kg/m2, with obesity further subcategorised to account for its severity (class I: 30 to <35, class II: 35 to <40, and class III: >40).
The primary cohort will be individuals with BMIs measured. The outcomes that will be assessed will include the following diseases and conditions: cardiovascular, cancers, respiratory, musculoskeletal, mental, neurological, and endocrine. How these will be categorised and defined are specified in the Appendices, as detailed in the ‘Outcomes to be Measured’ section.
The primary analysis will be discrete time-to-event Poisson regression, with age and calendar year as time-dependent covariates. This methodology will show the trends in rates of cause-specific mortality and morbidities, thus the changing rates of mortality from specific causes of death proportional to all-causes in overweight and obese individuals.
The outcomes to be measured will be stratified into three tiers of complexity for mortality and morbidity. Tier 1 is the broad category of conditions, Tier 2 includes specific categories of non-communicable diseases, and Tier 3 is cause-specific mortality or morbidity from each group of condition. The ICD-10 chapters and codes in addition to the categories for cause-specific mortality are in Appendix 1 and cause-specific morbidities are in Appendix 2.
Edward Gregg - Chief Investigator - Imperial College London
Marisa Sophiea - Corresponding Applicant - Imperial College London
Francesco Zaccardi - Collaborator - University of Leicester
Jonathan Pearson-Stuttard - Collaborator - Imperial College London
Edward Gregg - Collaborator - Imperial College London
HES Admitted Patient Care;HES Outpatient;ONS Death Registration Data;Patient Level Index of Multiple Deprivation;Practice Level Index of Multiple Deprivation