The metabolic syndrome predicts carotid intima-media thickness no better than the sum of individual risk factors in a lipid clinic population
Introduction
Metabolic syndrome (MS) is a clinical condition characterized by the concomitant occurrence of at least three out of five vascular risk factors (VRFs) including high blood pressure, central obesity, high triglycerides, low HDL-cholesterol and abnormal glucose levels.
On the basis of several epidemiological studies, the scientific community has accepted the MS as a predictor of cardiovascular disease [1], [2]. However, whether this syndrome is actually a distinct clinical entity is still a matter of debate [3], [4], [5], [6], [7]. Uncertainties include: (a) the lack of a recognized physiopathological common denominator, (b) the lack of proof that different clusters predict a similar risk of cardiovascular disease (CVD), (c) the lack of unique cutoffs for continuous variables such as waist and blood glucose, (d) the fact that the diagnosis is based on components that can change considerably over time, (e) the absence of a specific treatment for the syndrome beyond interventions for the management of its components, and, in particular, (f) the doubt that the pathogenic potential of MS goes beyond the pathogenic potential of its components [8].
Concerning the last point, the specific question is whether the elevated risk in MS derives from a real synergism between its components (positive interaction) or from a simple additive effect [9], [10], [11], [12]. This distinction is not trivial for the clinician, because the existence of synergism would warrant particular efforts to diagnose the disorder in order to improve individual risk assessment and/or prescribe a more aggressive treatment. Conversely, if the atherogenic effect of MS components is no more than additive, the physician's attention should be shifted from the diagnosis of MS to the identification and management of each vascular risk factor (VRF) whether it is a component of MS or not.
Several studies have investigated the question in general populations [9], [10], [11], [12]; most of them do not support the hypothesis of a synergistic effect of MS components on either subclinical carotid atherosclerosis or clinical events [10], [11], [12]. However, the diagnosis of MS is often made in selected high-risk subpopulations, such as those attending diabetes centers, hypertension units or lipid clinics. In these settings, the predictive value of MS diagnosis beyond that provided by its components might be different from that observed in general populations. In such patients the potential synergistic effects of MS components on atherosclerosis could be masked, unaffected, or even amplified. No data seem to have been reported on the significance of diagnosing MS in a Lipid Clinic. The only published study of the influence of MS on the extent of carotid atherosclerosis in hypercholesterolemic patients showed an increased C-IMT in those with MS, but the authors did not examine any putative synergism between the component risk factors [13].
Because of the relevance to the clinical practice of lipid specialists, we have investigated whether the MS is an independent determinant of carotid atherosclerosis above and beyond that expected from the sum of its components in patients attending a Lipid Clinic.
Section snippets
Study participants
Participants (n = 1804) were men (48%) and women (52%), 35–70 years old (mean ± SD: 56 ± 13 years), with no history of atherosclerotic vascular events, recruited among those attending for the first time the University Center for Dyslipidemias—E. Grossi Paoletti (Niguarda Hospital, Milan, Italy) since 2001. Patients attend our Lipid Clinic either spontaneously or referred by general practitioners and as such they can have mild to severe forms of dyslipidemias or a normal lipoprotein pattern.
Data on
Univariate analyses
Among the 1804 patients recruited in this study, 362 (20%) had MS. Compared to patients without MS, those with MS were older, contained more males and former smokers, and had a higher life-time exposure to cigarette smoking (Table 2 in supplementary material online). The total number of VRFs and the SPR were also significantly higher in the MS group. As expected, unadjusted C-IMT values were significantly greater in patients with MS than in those without (Table 2 in supplementary material online
Discussion
The present study addresses the pro-atherosclerotic nature of MS itself by using as endpoint the C-IMT, a well-accepted surrogate marker of carotid and even coronary atherosclerosis [20], [21], [22] and a recognized predictor of cardiovascular risk [23].
In order to make feasible the comparison of our results with those obtained in other populations, different statistical approaches were used to assess the value of the diagnosis of MS in determining C-IMT. All results agree in indicating that,
Conclusions
In conclusion, we have shown that in a lipid clinic population of Northern Italy including patients of both sexes, the diagnosis of MS was of no greater predictive value for carotid atherosclerosis than the sum of its components, and that the atherogenic potential of MS does not differ from other conditions with a similar total number of risk factors or risk estimation. Thus, from the point of view of clinical practice, efforts to diagnose MS in a lipid clinic setting may not be warranted,
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Relationship between carotid intima-media thickness and metabolic syndrome in adolescents
2013, Journal of PediatricsCitation Excerpt :Mittelman et al24 demonstrated that carotid IMT in children was related to BMI but not to fasting serum concentrations of total cholesterol, LDL-cholesterol, or triglycerides. Others reported no increased risk of MetS compared with the sum of its individual components based on carotid IMT measurements in adults.6,7 In children, MetS was no better at predicting increased IMT than BMI alone.25
T-wave axis deviation, metabolic syndrome and estimated cardiovascular risk - In men and women of the MOLI-SANI study
2013, AtherosclerosisCitation Excerpt :Differences between gender suggest a sexual dimorphism in the association between t-wave axis deviation and metabolic risk factors and it is in agreement with the notion that CAD risk is lower in women than in men [16]. The finding that T-wave axis deviation depends from single components of MetS is in line with other observations showing that MetS does not correlate with a measure of subclinical atherosclerosis to a greater extent than what expected from its individual components or from their total number [17] or with other studies performed in American or in European general populations using “hard” cardiovascular endpoints [18,19]. These findings, however, are not unexpected in syndromes whose signs and symptoms have a single underlying cause.
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The first two authors contributed equally to this work.