NEW YORK -- May 22, 2008 -- Metabolic syndrome, a combination of medical disorders thought to increase risk of both diabetes and cardiovascular disease (CVD), in fact is only associated with increased risk of diabetes in the elderly. This is the conclusion of authors of an article published early online and in an upcoming edition of The Lancet.
The metabolic syndrome criteria require individuals to have 3 of the 5 following abnormalities: raised blood sugar levels, high blood pressure, high waist circumference, decreased levels of high-density lipoprotein (HDL) cholesterol, and elevated levels of triglycerides. Criteria for metabolic syndrome were developed to improve understanding of links between the prediabetes state and heart disease and were touted to be a simpler way to simultaneously identify individuals at risk of either condition. However, their clinical role has remained very contentious since the criteria do not include other well-established risk factors for heart disease such as age, cholesterol, and smoking. Professor Naveed Sattar, BHF Glasgow Cardiovascular Research Centre, University of Glasgow, Glasgow, Scotland, and colleagues investigated to what extent metabolic syndrome and its individual components were related to risk of these 2 diseases in elderly populations.
Professor Sattar and colleagues addressed these issues in 2 prospective studies in elderly populations -- the Prospective Study of Pravastatin in the Elderly at Risk (PROSPER) and the British Regional Heart Study (BRHS). BRHS helped to corroborate and generalise results in PROSPER.
Investigators set out to determine to what extent metabolic syndrome and its individual components were related to risk for cardiovascular events and for incident type 2 diabetes in elderly people. Although many risk variables lessen in their association with vascular events in elderly populations, a large number of new-onset diabetes and increasingly more vascular events occur in this population, and so the results have both clinical and scientific value.
Data were analysed from 4,812 patients with diabetes aged 70 to 82 years from PROSPER and corroborated with the data in the second study (BRHS) in 2,737 male patients aged 60 to 79 years without diabetes. In PROSPER, 772 cases of CVD and 287 of diabetes occurred in just over 3 years. Metabolic syndrome was not associated with increased risk of CVD in those without baseline disease but was associated with a greater than 4-fold increased risk of diabetes.
Results were similar in participants with existing CVD. In BRHS, 440 cases of CVD and 105 of diabetes occurred over 7 years. Metabolic syndrome was associated with a 27% increased risk of CVD, but a more than 7-fold increased risk of diabetes. In both studies, body mass index or waist circumference, triglyceride levels, and glucose cut-off points were not associated with risk of CVD, but all 5 components were associated with risk of new-onset diabetes.
The investigators report, "Metabolic syndrome and its components are associated with type 2 diabetes but have weak or no association with vascular risk in elderly populations, suggesting that attempts to define criteria that simultaneously predict risk for both cardiovascular disease and diabetes are unhelpful." They concluded that rather than having combined criteria, clinical focus should remain on establishing optimum risk algorithms for each disease. In fact, PROSPER and BRHS demonstrated that a fasting plasma glucose test is as good as or potentially better than a diagnosis of the metabolic syndrome for predicting diabetes.
In an accompanying Comment, Dr. Richard Khan, American Diabetes Association, Alexandria, Virginia, remarked, "What seems to make most sense is for clinicians to focus on global risk assessment that takes into account all the well-established cardiometabolic risk factors and then to treat each abnormality appropriately. Also, more research is needed to understand the cause of risk-factor clustering and the pathogenesis of insulin resistance. Both actions would better serve the health of those at risk of diabetes and cardiovascular disease than seeking a diagnosis of the metabolic syndrome."
SOURCE: The Lancet
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