Metabolic syndrome — a combination of medical disorders thought to increase risk of both diabetes and cardiovascular disease (CVD) — in fact only increases the 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 three of the five following abnormalities: raised blood sugar levels, high blood pressure, high waist circumference, decreased levels of the healthy cholesterol (called HDL cholesterol), and elevated levels of triglycerides (fats) in the blood. Criteria for metabolic syndrome were developed to improve understanding of links between the pre-diabetes 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 remains 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, UK, and colleagues investigated to what extent metabolic syndrome and its individual components were related to risk of these two diseases in elderly populations.
They analysed data from 4812 non-diabetic people aged 70-82 years from the Prospective Study of Pravastatin in the Elderly at Risk (PROSPER), and corroborated this data in a second prospective study (the British Regional Heart Study [BRHS]) of 2737 non-diabetic men aged 60-79 years. In PROPSER, 772 cases of CVD and 287 of diabetes occurred in just over three years. Metabolic syndrome was not associated with increased risk of CVD in those without baseline disease, but was associated with a more-than-four-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 seven years. Metabolic syndrome was associated with a modest (27%) increased risk of CVD, but a more than seven-fold increased risk of diabetes. In both studies, body mass index or waist circumference, triglyceride levels, and glucose cutoff points were not associated with risk of cardiovascular disease, but all five components were associated with risk of new-onset diabetes.
The authors say: “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 conclude that rather than having a combined criteria, clinical focus should remain on establishing optimum and separate risk criteria for each disease.
In an accompanying Comment, Dr Richard Khan, American Diabetes Association, Alexandria, VA, USA, discusses the concept of metabolic syndrome and poses some questions as to its usefulness compared with other cardiovascular risk-factor tests. He concludes: “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.”
Note to editors: *please see figure in full comment for list of risk factors
Professor Naveed Sattar, BHF Glasgow Cardiovascular Research Centre, University of Glasgow, UK T) +44 (0) 7971 189415 E) nsattar@clinmed.gla.ac.uk
Dr Richard Kahn, American Diabetes Association, Alexandria, VA, USA T) +1 703-299-2065 E) rkahn@diabetes.org
http://www.eurekalert.org/jrnls/lance/pdfs/Metaboliccommentfinal.pdf
http://www.eurekalert.org/jrnls/lance/pdfs/metabolicfinal.pdf.pdf
Journal
The Lancet