Published online before print September 18, 2008, doi: 10.1161/STROKEAHA.108.523837
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(Stroke. 2008;39:e163.)
© 2008 American Heart Association, Inc.
Letters to the Editor |
Metabolic Syndrome and Stroke
U.S. Department of Health and Human Services, Kansas City, Mo
To the Editor:
In an interesting study of 991 members of a Finnish cohort,1 Wang et al found that 5 definitions of metabolic syndrome (MS) were associated with the risk of all types of stroke combined, and 3 components of MS—glucose intolerance, insulin resistance and central obesity—were independently associated with stroke. The sixth definition (American College of Endocrinology [ACE] definition) of MS did not include obesity as a component of MS but raised body mass index was regarded as a risk factor for MS.2 If Wang et al had restricted their study to ischemic stroke, they might have found MS by ACE definition also to be associated with stroke. Their findings are not surprising because the components of MS (obesity, hypertension, fasting glucose, triglycerides, and HDL-cholesterol) are known risk factors for type 2 diabetes or coronary artery disease and ischemic stroke. However, why is it necessary to combine these risk factors into a syndrome and determine its association with stroke?
The components of MS are pathophysiological parameters, not symptoms, disease states, or disabilities that could be grouped as a syndrome. The underlying pathophysiology of MS and its value as a diagnosis are unclear, and its usefulness as a marker of cardiovascular disease risk above and beyond the risk associated with individual components is uncertain.3 MS is not included in the international classification of diseases (ICD) by any of the 6 definitions. The ICD-9-CM code 277.7 is for dysmetabolic syndrome X defined as a "group of metabolic disorders that are related to insulin resistance without elevated blood sugars." By definition, the diagnosis of MS requires any 3 of its 5 components.4 Accordingly, 2 patients with MS can share only 1 of its 5 components. In others, additional risk factors, outside the definition of MS, may be prevalent. The 6 definitions of MS differ from each other with respect to the cutoffs of the parameters. Consequently, a patient with 3 to 5 components may be diagnosed as a case of MS by one definition, not by other definitions.4 Why not just treat individual risk factors for cardiovascular diseases, stroke, and other complications of diabetes whether they fit into a definition of MS or not?
Defendants of MS contend that identification of one risk factor in a patient would prompt a search for other factors,3 but the search can be initiated without the label of MS and impaired glucose tolerance alone is better than MS in predicting diabetes.3–5 Labeling patients with MS can be counterproductive because it could create the impression that its underlying pathophysiology is clear and that it denotes greater risk than that from its components.3 Some argue that the label of MS should be retained because it helps to identify people in a risk state similar to that of dislipidemia, so that physicians can focus on them.6 In practice, patients at risk of cardiovascular diseases are being identified without the diagnosis of MS. Why confuse the situation with a new, unnecessary syndrome that has multiple definitions, each with different cutoff points for the parameters? To compound the confusion, the definition of MS proposed by the International Diabetes Federation5 detects overt diabetes and cardiovascular disease, yet it also predicts these outcomes.7 The diagnosis of MS is redundant in those who already have diabetes and adds nothing to the management of those who do not.7 Raven, who introduced the concept of MS,8 acknowledges that MS occurs only in insulin resistant persons and a diagnosis of MS has neither pedagogical nor clinical use.9
Future research should be directed toward the prevention, control and treatment of individual components of MS, not the syndrome.
Acknowledgments
Disclosures
None.
References
1. Wang J, Ruotsalainen S, Moilanen L, Lepisto P, Laakso M, Kuusisto J. The metabolic syndrome predicts incident stroke: a 14-year follow-up study in elderly people in Finland. Stroke. 2008; 39: 1078–1083.
2. American College of Endocrinology. Insulin resistance syndrome. Available at: http://www.euchromatin.org/IRS02.htm. Accessed April 15, 2008.
3. Kahn R, Buse J, Ferrannini E, Stern M. The metabolic syndrome: time for a critical appraisal. Diabetes Care. 2005; 28: 2289–2304.
4. Reaven GM. The metabolic syndrome: requiescat in pace. Clin Chem. 2005; 51: 931–938.
5. Alberti KG, Zimmet PZ, Shaw J. Metabolic syndrome: a new world-wide definition. A consensus statement from the International Diabetes Federation. Diabetes Med. 2006; 23: 469–480.[CrossRef][Medline] [Order article via Infotrieve]
6. Alberti KG, Zimmet PZ. Should we dump the metabolic syndrome? No. BMJ. 2008; 336: 641.
7. Gale EAM. Should we dump the metabolic syndrome? Yes. BMJ. 2008; 336: 640.
8. Reaven GM. Role of insulin resistance in human disease. Diabetes. 1988; 37: 1595–1607.[Abstract]
9. Reaven GM. The metabolic syndrome: is this diagnosis necessary? Am J Clin Nutr. 2006; 83: 1237–1247.
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