More evidence against concept of "metabolic syndrome"

More evidence against concept of "metabolic syndrome"
May 20, 2010 Sue Hughes

Hamilton, ON - Patients with metabolic syndrome are no more at risk of future MI than those with diabetes or hypertension alone, a new study suggests [1].

The study, published in the May 25, 2010 issue of the Journal of the American College of Cardiology, was conducted by a group led by Dr Andrew Mente (McMaster University, Hamilton, ON).

Mente commented to heartwire: "Our study examined whether we need to look at metabolic syndrome as a distinct entity or whether we should instead be focusing on the individual risk factors, and we found that the individual risk-factor approach is probably best. The results strongly suggest that we should be treating the individual risk factors rather than metabolic syndrome."

The results strongly suggest that we should be treating the individual risk factors rather than metabolic syndrome. In the paper, the researchers explain that the common clustering of metabolic abnormalities, including abdominal obesity, elevated glucose, abnormal lipids, and elevated blood pressure is often referred to as the metabolic syndrome. While metabolic syndrome is associated with an increased risk of coronary heart disease, it is not known whether this risk is greater than that conferred by its constituent components, and the value of classifying subjects with metabolic syndrome has recently been called into question.

To investigate this issue, Mente et al analyzed data from the INTERHEART study, a case-control study of incident acute MI that involved 12 297 cases and 14 606 controls from 52 countries. They classified the study participants using the World Health Organization (WHO) and International Diabetes Federation (IDF) criteria for metabolic syndrome, and their risks for MI were compared with the individual metabolic-syndrome component factors. Results showed that metabolic syndrome was associated with a two- to three-times increased risk of MI, but the same risk was conferred by having either hypertension or diabetes alone.

Adjusted odds ratio for MI associated with metabolic syndrome or its component factors

Risk factor
OR (95% CI)

Metabolic syndrome (WHO definition)
2.69 (2.45-2.95)

Metabolic syndrome (IDF definition)
2.20 (2.03-2.38)

Diabetes
2.72 (2.53-2.92)

Hypertension
2.60 (2.46-2.76)

Abdominal obesity (WHO definition)
1.64 (1.55-1.74)

Abdominal obesity (IDF definition)
1.32 (1.25-1.39)

Low HDL
1.30 (1.22-1.37)


To download table as a slide, click on slide logo above

Mente noted: "People who advocate for the metabolic syndrome concept believe that when the component risk factors occur together this would have an additive or greater effect on risk, and therefore it is important to identify these individuals. But we didn't find that. So our study adds to the evidence that a diagnosis of metabolic syndrome is not useful. It is better just to treat the actual risk factors."

The researchers also looked at subthreshold values for the risk factors making up the metabolic syndrome—ie, levels higher than normal but below the levels that define diabetes, hypertension, low HDL or abdominal obesity. They found that there appeared to be a dose-response relationship between MI and risk-factor measures, and an aggregation of risk factors with values below their threshold was associated with a significantly greater risk of MI, compared with having component factors with normal values (OR 1.5), but lower than the risk conferred by an aggregation of risk factors with values above the threshold points.

They write: "These findings of a dose-response relationship between risk-factor severity and MI risk suggest that a standard definition of metabolic syndrome loses information when continuous variables are converted to categorical variables and provide support for calls to replace the categorical definition of metabolic syndrome with a scoring system that may involve each risk factor being assigned a weight based on its level and a regression formula developed to estimate risk."

Yes, in my opinion this should be the end of the metabolic syndrome. To heartwire, Mente added: "This is another knock against the diagnosis of metabolic syndrome. It is not a case of 'Yes, you are at increased risk' or "No, you are not at increased risk.' Risk increases incrementally, and if we use the definition of metabolic syndrome, we would not catch any of the patients with these subthreshold increases in risk factors."

Asked whether there is now enough evidence to do away with the concept of metabolic syndrome, Mente replied: "We are seeing a little more evidence with each study. It gets to a point where the evidence becomes overwhelming. It is hard to say if we are there yet. Our findings are consistent with at least a couple of other studies, and, yes, in my opinion this should be the end of the metabolic syndrome. But there might be some who disagree."

This study was supported by the Canadian Institutes of Health Research, the Heart and Stroke Foundation of Ontario, the International Clinical Epidemiology Network, and unrestricted grants from several pharmaceutical companies (with major contributions from AstraZeneca, Novartis, Hoechst Marion Roussel [now Sanofi-Aventis], Knoll Pharmaceuticals [now Abbott], Bristol-Myers Squibb, and Sanofi-Synthélabo). The authors do not report any other disclosures.


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Source
1.Mente A, Yusuf S, Islam S, et al. Metabolic syndrome and risk of acute myocardial infarction. A case-control study of 26 903 subjects from 52 countries. J Am Coll Cardiol 2010; 55:2390-2398.


Artículo completo: http://www.theheart.org/article/1080363.do