Two major health organizations in Europe and the United States are calling for closer examination of a syndrome that has been widely believed to predict the risk of developing heart disease, questioning whether it has been appropriately defined and whether it is in fact a syndrome at all.
In a joint paper published in the September issue of Diabetes Care and Diabetologia, the American Diabetes Association and European Association for the Study of Diabetes argue that the metabolic syndrome -- which has come to be regarded as a predictor of cardiovascular disease -- is poorly defined, inconsistently used and in need of further research to help understand whether and how it should be treated. Doctors, the authors warn, should not be diagnosing people with this "syndrome" or attempting to treat it as a separate malady until the science behind it is clear.
"We shouldn't be diagnosing people with the 'metabolic syndrome.' Doing so misleads the patient into believing he or she has a unique disease. What they really have are well-known cardiovascular risk factors. The combination of risk factors does not add up to a more significant or higher cardiovascular risk than the individual components," according to Richard Kahn, PhD, Chief Scientific and Medical Officer of the American Diabetes Association.
The metabolic syndrome is often defined as having any three or more of the following: a large waist circumference; high triglyceride levels; high blood pressure; low HDL ("good") cholesterol; and high blood glucose levels. The World Health Organization offers a different definition, including anyone who has diabetes or insulin resistance and two of the following: high waist-to-hip ratio; high triglycerides or low HDL cholesterol; high blood pressure; and a high urinary albumin excretion rate. Other organizations have put forth yet other definitions.
Consequently, studies showing a correlation between a combination of these factors and the risk of developing heart disease are highly inconsistent. The fact that these are conflicting definitions implies that there is no clear evidence base for what should or should not be included, the authors note.
Taken individually, each of the above conditions is considered a risk factor for cardiovascular disease and should be treated as such, the authors state. "But there is no combination of risk factors that boosts a person's cardiovascular risk beyond the sum of the parts, or constitutes a separate disease," said Ele Ferrannini, MD, President of the European Association for the Study of Diabetes.
In patients with diabetes or known vascular disease, inordinate attention to the 'metabolic syndrome' can impede appropriate care. Similarly, treatment of each and every metabolic risk factor is indicated without requiring some arbitrary combination to drive clinical decision-making.
"The metabolic syndrome requires much more study before its designation as a "syndrome" is truly warranted and before its clinical utility is adequately defined," the authors wrote in their conclusion.
In the meantime, the paper recommends that doctors continue to evaluate patients for the presence of other cardiovascular risk factors when one is discovered; aggressively treat individual cardiovascular risk factors; avoid labeling patients with the term "metabolic syndrome;" and not attempt to prescribe a treatment for this "syndrome" until new, solid evidence is obtained.