Friday, August 26, 2005

Physicians Should Treat All Cardiovascular Risk, Not Just Metabolic Syndrome

Aug. 25, 2005 — A joint statement from the Professional Practice Committee of the American Diabetes Association (ADA) and the European Association for the Study of Diabetes (EASD), published in the September issue of Diabetes Care, advises physicians not to diagnose or treat the metabolic syndrome. Rather, the statement suggests that they should treat all cardiovascular (CV) risk.

"The term 'metabolic syndrome' refers to a clustering of specific cardiovascular disease (CVD) risk factors whose underlying pathophysiology is thought to be related to insulin resistance," write Richard Kahn, PhD, from the ADA in Alexandria, Virginia, and colleagues. "While there is no question that certain CVD risk factors are prone to cluster, we found that the metabolic syndrome has been imprecisely defined, there is a lack of certainty regarding its pathogenesis, and there is considerable doubt regarding its value as a CVD risk marker."

In recent decades, investigators identified clustering of certain CVD risk factors including obesity, type 2 diabetes, hyperlipidemia, and hypertension. Hyperinsulinemia was also linked to hyperlipidemia, obesity, and hypertension; and a cluster of CVD risk factors seemed to underlie type 2 diabetes. In association with insulin resistance, risk factor clustering led to the description of a unique pathophysiologic condition termed the "metabolic" or "insulin resistance" syndrome.

On Jan. 28, 2005, the authors performed a Medline search using the keywords "syndrome X" or "insulin resistance syndrome" or "metabolic syndrome," identifying 4,646 citations, including 3,948 studies performed on human subjects. Definitions for "metabolic syndrome" have been proposed by the World Health Organization (WHO) and the Third Report of the National Cholesterol Education Program's Adult Treatment Panel (ATP III), as well as by other organizations.

This review critically examined the evidence underlying the definition of the metabolic syndrome, as well as its pathogenesis, association with CVD, and impact of treatment. The primary focus was on articles addressing the metabolic syndrome as defined by ATP III, with a view toward answering three main questions: (1) How clear is the existing definition of the metabolic syndrome for diagnostic purposes?; (2) Does the treatment of metabolic syndrome differ from treatment of its individual components?; and (3) What additional research is needed to improve current knowledge of this syndrome?

"Until much needed research is completed, clinicians should evaluate and treat all CVD risk factors without regard to whether a patient meets the criteria for diagnosis of the 'metabolic syndrome,'" the authors write. "Our analysis indicates that too much critically important information is missing to warrant its designation as a 'syndrome.'"

Until additional studies address unanswered questions, the authors recommend that patients with diabetes or clinical CVD should be excluded from the case definition of metabolic syndrome; that adults with any major CVD risk factor should be evaluated for the presence of other CVD risk factors; that patients with CVD risk variables over normal limits should be counseled regarding lifestyle modification; that those with markers indicating overt disease (such as blood pressure higher than 140/90 mmHg or fasting plasma glucose level at 7.0 mmol/L or more) should be treated according to established guidelines; and that all CVD risk factors should be individually and aggressively treated.

"Providers should avoid labeling patients with the term 'metabolic syndrome,' as this might create the impression that the metabolic syndrome denotes a greater risk than its components, or that it is more serious than other CVD risk factors, or that the underlying pathophysiology is clear," the authors conclude. "Until randomized controlled trials have been completed, there is no appropriate pharmacological treatment for the metabolic syndrome, nor should it be assumed that pharmacological therapy to reduce insulin resistance will be beneficial to patients with the metabolic syndrome."

Diabetes Care. 2005;28:000-000