Relationship between Body Mass Index (BMI) trajectory and the risk of cardiovascular disease and diabetes among overweight and obese people: A UK Primary Care-based cohort study

Date of ISAC Approval: 
07/08/2018
Lay Summary: 
Obesity, an excess of body weight, increases the risk of chronic diseases such as heart disease, stroke, diabetes, lung disease, cancers and premature death. Body mass index, a measure of overall body fat, is calculated as weight in kilograms divided by height in metres squared (kg/m2). Obesity is rising in the UK, leading to growing concerns over its long-term impact on health. As such, health care professionals are working on ways to prevent, manage and reverse this problem. Changes in weight lead to changes in the factors that affect the risk of heart disease and diabetes. There is, however, not enough evidence of the effect of weight changes among overweight and obese people, on the future risk of developing heart disease, stroke and type-2 diabetes. This study aims to use patient records to determine the effect of changes in body mass index over a specified period on the risk of having a heart attack or type-2-diabetes in patients who are obese or overweight. Findings from this study will provide new knowledge and guidance on the effect of body mass index changes on the risk these disease conditions, as well as help clinicians effectively manage these group of patients.
Technical Summary: 
Background: Existing evidence indicate changes in weight lead to changes in the risk factors for cardiovascular disease (CVD) and type-2-diabetes mellitus (T2DM). However, there is insufficient knowledge of the effects of body mass index (BMI) changes on the overall risk of CVD and T2DM in overweight/obese patients. Objectives: 1. To identify BMI change patterns over time in obese and overweight individuals 2. To determine the relationship between distinct BMI trajectories and CVD and T2DM outcomes Study design: Cohort design Setting: UK General Practice Participants: Adult patients free from CVD or T2DM at baseline, registered for at least one year before the study start date, with a baseline BMI of 25kg/m2 or greater and minimum of 3 BMI readings during the study period. Outcome: Incident CVD and T2DM diagnosis Methods: For each patient, 4 measurements of BMI over a 10 year period will be collected (at baseline, 2, 5 and 10 years). Using latent class analysis, distinct BMI trajectory groups will be identified and the relationship between BMI trajectories with CVD and T2DM assessed. Outputs: Distinct BMI trajectories for overweight and obese patients. Significance and effect of the association between BMI trajectories and CVD as well as T2DM.
Health Outcomes to be Measured: 
Primary outcome - Incidence of cardiovascular disease associated with variation in BMI over time, among individuals who are overweight or obese Secondary outcome - Incidence of Type 2 diabetes associated with variation in BMI over time, among individuals who are overweight or obese
Collaborators: 

Dr Barbara Iyen - Chief Investigator - University of Nottingham
Dr Barbara Iyen - Corresponding Applicant - University of Nottingham
Professor Joe Kai - Collaborator - University of Nottingham
Professor Nadeem Qureshi - Collaborator - University of Nottingham
Dr Ralph Kwame Akyea - Collaborator - University of Nottingham
Dr Stephen Weng - Collaborator - University of Nottingham
Yana Vinogradova - Collaborator - University of Nottingham

Linkages: 
HES Admitted;ONS;Patient IMD