Metabolic Syndrome and Early Death
To the Editor:
The editorial by Franks and Olsson1 highlights the heterogeneous nature of definitions of the metabolic syndrome, which results from the number of different combinations of risk factors that equate with a diagnosis of the syndrome.
However, the situation is even more complex than indicated in Figure 2 of their editorial. There are, in fact, 16 permutations of components of the metabolic syndrome as defined by the Adult Treatment Panel III definition2: 10 for combinations of 3 metabolic syndrome components, 5 for combinations of 4 metabolic syndrome components, and 1 for the combination of all 5 metabolic syndrome components (Table). The situation is similar for the International Diabetes Federation definition of the metabolic syndrome in which there are 11 possible combinations in people who meet the abdominal obesity criteria.3
Studies that we are currently undertaking show that the prevalence of each of these individual combinations varies considerably within and between populations. In addition, as shown in the Pressioni Arteriose Monitorate e Loro Associazioni Study, outcomes may also differ according to particular combinations of risk factors used to diagnose the metabolic syndrome.4
The limitations of approaches that count metabolic risk factors using artificial thresholds were highlighted recently by our group in an analysis of >300 000 subjects.5 Statistical models using the “3 or more positive” rule performed much poorer than models that scored the number (of 5) risk factors positive (on a 0 to 5 scale), whereas each was dominated significantly by a model that took all 5 of the metabolic risk factors as continuous variables.
Although the metabolic syndrome may be useful for epidemiological studies and as a public health message, the above observations highlight the limitations of the clinical implications of a diagnosis of the metabolic syndrome in individual patient care.
Franks PW, Olsson T. Metabolic syndrome and early death. getting to the heart of the problem. Hypertension. 2007; 49: 10–12.
Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. Executive summary of the third report of the National Cholesterol Education Program (NCEP) expert panel on detection, evaluation and treatment of high blood cholesterol in adults (Adult Treatment Panel III). JAMA. 2001; 285: 2486–2497.
International Diabetes Federation. The IDF consensus worldwide definition of the metabolic syndrome; 2005. Available at: http://www.idf.org/webdata/docs/MetSyndrome_FINAL.pdf. Accessed March 2, 2007.
Mancia G, Bombelli M, Corrao G, Facchetti R, Madotto F, Giannattasio C, Trevano FQ, Grassi G, Zanchetti A, Sega R. Metabolic syndrome in the Pressioni Arteriose Monitorate e Loro Associazioni (PAMELA) Study. Daily life blood pressure, cardiac damage, and prognosis. Hypertension. 2007; 49: 40–47.