The Association of Blood Glucose and Diabetes with Abdominal Aortic Aneurysm, Carotid Stenosis and Peripheral Arterial Disease: An Observational Study of 630,000 Patients Attending Vascular Screening

Abstract

Introduction - Diabetes is an important risk factor for atherosclerotic vascular disease, and previous studies have also shown a positive continuous association between blood glucose concentrations throughout the “normal” reference range and cardiovascular disease. However, diabetes appears to be inversely associated with abdominal aortic aneurysm (AAA). This study reports associations between blood glucose concentration and diabetes with AAA, carotid stenosis and peripheral arterial disease (PAD). Methods - Between 2008 and 2013, 3.3 million self-referred individuals attended cardiovascular screening clinics (Life Line Screening) in the US and UK. Assessments included an aortic ultrasound scan, a carotid duplex, and ankle-brachial pressure index (ABPI). Major cardiovascular risk factors and medical history were recorded, and approximately one fifth of participants also underwent blood glucose assays. Diabetes was defined according to previous diagnosis or treatment. Participants with incomplete data or prior cardiovascular disease were excluded, yielding 628 246 individuals in the current report. Results - The mean age at screening was 63 ± 10 years, and 64% of attendees were women. The following prevalences were observed: AAA (infra-renal aorta ≥ 30mm) = 0.5%; carotid artery stenosis (peak systolic velocity generally ≥110cm/s) = 3.5%; PAD (ABPI <0.9) = 2.6%. A prior diagnosis of diabetes was associated with higher risk of PAD (OR, 95%CI: 1.77, 1.71-1.84) and carotid stenosis (1.71, 1.66-1.76), and among participants without a prior diagnosis of diabetes the prevalence of carotid stenosis and PAD increased with higher blood glucose levels across the normal reference range. For AAA, a prior diagnosis of diabetes was associated with a significantly lower risk (0.83 0.77-0.90), however among attendees without diabetes, the prevalence of AAA increased with higher blood glucose levels across the normal reference range. Conclusion - Across the normal reference range, higher blood glucose concentrations are associated with increased risk of carotid stenosis, PAD and AAA, but a diagnosis of diabetes was associated with a lower risk of AAA. This raises the possibility that the “protection” conferred by diabetes against AAA could be due to a treatment effect, but this hypothesis needs to be tested in randomised trials.