Metabolic syndrome and incidence of type 2 diabetes in patients with manifest vascular disease

Risk reduction in patients with clinically manifest vascular disease focuses on preventing new vascular events and not on prevention of type 2 diabetes. However, given the common pathophysiological pathways involved in the development of atherosclerosis and type 2 diabetes, it is probable that people with atherosclerotic vascular disease have an elevated risk of type 2 diabetes. The present prospective cohort study investigated the incidence of type 2 diabetes and the effect of the presence of metabolic syndrome on the incidence of type 2 diabetes in 4,022 patients with clinically manifest atherosclerosis, included in the study from September 1996 to June 2006. Patients who died (n=456), who were lost to follow-up (n=84) and those with diabetes at baseline (n=558) were excluded, leaving 2,924 patients for analysis. The incidence of diabetes was assessed by questionnaire (self-reported diabetes). During 13,726 person-years of follow-up (median follow-up 4.3 years, range 2.4–7.0 years), there were 152 type 2 diabetes cases (5.2%), corresponding to an incidence rate of 11.1 (95% CI 9.4–13.0) per 1,000 person-years. Patients with metabolic syndrome were at increased risk of incident type 2 diabetes compared to those without metabolic syndrome, with an adjusted hazard ratio of 5.7 (95% CI 3.7–8.9) for Revised National Cholesterol Education Program, 6.0 (4.1–9.0) for National Cholesterol Education Program and 4.0 (2.7–6.1) for International Diabetes Federation definitions of metabolic syndrome. Of all metabolic syndrome components, abdominal obesity was most strongly associated with incident type 2 diabetes (94% higher risk of type 2 diabetes for 1 standard deviation (11.3 cm) increase in waist circumference). In conclusion, patients with manifest atherosclerosis are at high risk of developing type 2 diabetes. Metabolic syndrome identifies those at the highest risk and is an easy to use clinical tool. Abdominal obesity is a strong individual predictor of type 2 diabetes. Patients with manifest atherosclerosis and metabolic syndrome may derive particular benefit from lifestyle interventions focusing on weight reduction.