Background: The increasing prevalence of obesity has recently become a major public health concern. Controversy has arisen regarding how best to characterise this risk with several definitions of a “metabolic syndrome” (MS) proposed to identify those at greatest risk. Controversy has arisen regarding the ability of these definitions to predict cardiovascular risk. We assessed the relationship between MS criteria and arterial phenotype in a large population based cohort.

Methods: 3437 British civil servants aged 51–74 who were free from clinical cardiovascular disease and diabetes mellitus were studied (Whitehall II study). RFs were measured and carotid intima-media thickness (cIMT) assessed. Participants were categorised into 3 groups according to IDF and ATP_III criteria; Groups 1 (no MS; n=2712); 2 (MS by IDF criteria only; n=349); 3 (MS by ATP_III only or both ATP_III and IDF criteria; n=376).

Results: cIMT was increased in groups 2 and 3 compared to controls (both p<0.001). These differences remained after adjusting for other RFs. Groups 2 and 3 had similar cIMT. In addition, non obese participants with one or more MS risk factors (defined by IDF criteria) had significantly greater cIMT compared to controls (p<0.001), an association that remained after further adjustment for RFs.

Conclusion: MS, defined by both ATP_III and the recent IDF criteria, identifies a population with increased cIMT. However, we also show that restricting the diagnosis of MS to those with abdominal obesity, as recommended by the IDF, may miss an important population with MS risk factors who have an adverse vascular phenotype.