Respected healthcare experts are struggling to understand the importance of a set of troubling health conditions known as “metabolic syndrome,” a term used to identify the presence of multiple risk factors for heart disease, stroke, and other types of cardiovascular disease (CVD). In September 2005, the American Heart Association (AHA) and the American Diabetes Association (ADA) issued conflicting statements. The ADA said that more research is needed before treatment of metabolic syndrome may make a difference in patient care while the AHA forged ahead with guidelines to define, diagnose, and treat the syndrome as a distinct condition.

Risk factors for “metabolic syndrome” include high blood pressure, high risk lipid profile (high LDL, low HDL, high triglycerides), obesity (especially fat around the waist), and high blood glucose (either prediabetes, diabetes, or insulin resistance) along with some markers of inflammation. While all of these conditions are known risk factors, there is debate over what the presence of multiple conditions in one person means. Does the presence of several risk factors increase the risk disproportionately? Is standard treatment of each risk factor alone appropriate or should a different approach be used when several risk factors are present together?

In September 2005, the ADA said in a statement issued jointly with the European Association for the Study of Diabetes that metabolic syndrome is an inadequately defined concept and that (1) does not meet the medical definition of a syndrome and (2) does not change how each individual aspect is medically managed. The AHA along with the National Heart, Lung, and Blood Institute (NHLBI), on the other hand, published guidance on classifying, diagnosing, and medically managing an individual with metabolic syndrome. They also called for more research in this area.

This difference in opinion among well-respected health organizations exemplifies the need for an evidence-based approach. Evidence-based medicine (EBM) is a relatively new term that describes a formalized system for helping the medical community to cope with the vast amount of medical data that exists and to develop formal protocols based on the best data supporting the best health outcomes. By sifting through large volumes of information, doctors can identify the best diagnostic tests and treatments. But this requires that clear evidence exists from well-performed clinical trials that have patient outcomes as endpoints.

The disagreement on metabolic syndrome seems to stem from dissenting opinions on the existing data and the need for more research to continue to address the key clinical questions. The ADA explained that “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.” Their extensive review of published research led them to conclude that “too much critically important information is missing to warrant its designation as a ‘syndrome.’” Their recommendation: 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.

While the ADA was dismissing the concept as clinically useful, at least for now, the AHA, in collaboration with the NHLBI, has been trying to advance it. They admit that the conditions that make up metabolic syndrome have more than one cause, but are confident that these conditions in combination contribute to type 2 diabetes and atherosclerotic CVD. The AHA report’s authors noted differences between the diagnostic criteria given by various groups, but were not put off by them. The World Health Organization, for example, has its list of diagnostic criteria and the European Group for Study of Insulin Resistance has proposed a modification of it. The National Cholesterol Education Program’s Adult Treatment Panel III (ATP III), meanwhile, has outlined its own criteria, and both the American Association of Clinical Endocrinologists and International Diabetes Foundation think modifications of that are useful. Like these last three groups, the AHA and NHLBI generally accept the ATP III diagnostic criteria; they say they are easy to use and have modified them only slightly. In essence, the AHA and NHLBI say that an individual with certain abnormal measurements in just three of the following areas—abdominal obesity, lipids, blood pressure, and fasting plasma glucose—should be diagnosed and treated for metabolic syndrome. Markers of inflammation and the tendency to develop blood clots are also important to watch, they say.

For a patient, conflicting pronouncements such as those of the ADA and the AHA can be confusing and frustrating. However, the bottom line remains the same: you should work with your doctor to determine the appropriate course of action based on your medical history and what the two of you are comfortable with as a treatment approach. Research will continue to be conducted that may eventually help us define metabolic syndrome and how it should be managed so that a consensus can be reached among health care providers and organizations.

Sources
S1
Kahn R, Buse J, Ferrannini E and Stern M, for the American Diabetes Association and the European Association for the Study of Diabetes. The metabolic syndrome: time for a critical appraisal (ADA statement). Diabetes Care. 2005;28:2289-2304.

S2
Grundy S, Cleeman JI, Daniels SR, et al, for the American Heart Association and the National Heart, Lung, and Blood Institute. Diagnosis and management of the metabolic syndrome (scientific statement). Circulation. 2005;112:2735-52.

S3
American Heart Association and National Heart, Lung, and Blood Institute. Metabolic syndrome: new guidance for prevention and treatment (scientific statement). Journal Report. 13 Sep 2005.