The relationship between diabetes, obesity and cardiovascular disease phenotypes: a UK Biobank cohort study

Introduction Obesity and diabetes mellitus (DM) frequently co-exist, yet their individual contributions to cardiovascular risk remain debated. We explored cardiovascular disease biomarkers, events and mortality in a large cohort stratified by body mass index (BMI) and DM. Methods 451,355 UK Biobank participants were stratified by ethnicity-specific BMI categories (normal, overweight, obese) and DM status. We examined cardiovascular biomarkers including: carotid intima-media thickness (CIMT); arterial stiffness; left ventricular ejection fraction (LVEF) and cardiac contractility index (CCI). Poisson regression models estimated adjusted incidence rate ratios (IRR) for myocardial infarction, ischaemic stroke and cardiovascular death, with normal weight non-DM as comparator. Results 5% of participants had DM (10% normal weight, 34% overweight and 55% obese; versus 34%, 43% and 23%, respectively, in non-DM). In the non-DM group, overweight/obesity was associated with higher CIMT, arterial stiffness and CCI, and lower LVEF (p<0.05); these relationships were diminished in the DM group. Within BMI classes, DM was associated with adverse cardiovascular phenotype (p<0.05), particularly in the normal weight group. After 5,323,190 person-years follow-up, incident myocardial infarction, ischaemic stroke and cardiovascular mortality all rose across increasing BMI categories in the DM and non-DM groups (p<0.05). However, normal weight DM had higher cardiovascular mortality than obese non-DM (IRR 2.81 [95% confidence interval: 2.24-3.54] vs IRR 1.84 [1.70-1.98]). Conclusions Obesity and DM are additively associated with adverse cardiovascular biomarkers and mortality risk. Whilst adiposity metrics are more strongly correlated with cardiovascular biomarkers than diabetes-oriented metrics, both correlate weakly, suggesting other factors underpin the high cardiovascular risk of normal-weight diabetes.