Elderly people who suffer from metabolic syndrome have an increased risk of diabetes, not cardiovascular disease (CVD), according to a paper published online in The Lancet. Previously, metabolic syndrome (a combination of medical disorders) was thought to increase the risk of both diabetes and (CVD).
Having three of the following five abnormal medical conditions lead to a diagnosis of metabolic syndrome:
- raised blood sugar levels
- high blood pressure
- high waist circumference
- decreased levels of good (HDL) cholesterol
- elevated levels of triglycerides (fats) in the blood
These criteria were designed to enhance our understanding of how heart disease is related to the pre-diabetes state and heart disease. Though the medical community has accepted them as a convenient method of identifying individuals at risk for both conditions at the same time, there is still debate about their clinical role because age, cholesterol, smoking, and other well established risk factors for heart disease are omitted. To add clarity to this discussion, Professor Naveed Sattar (BHF Glasgow Cardiovascular Research Centre, University of Glasgow, UK) and colleagues analyzed how metabolic syndrome and its components were associated with the risk of diabetes and CVD in elderly populations.
Data from the Prospective Study of Pravastatin in the Elderly at Risk (PROSPER) enabled the researchers to assess 4812 non-diabetic people from age 70 to 82, and data from the British Regional Heart Study (BRHS) contained 2737 non-diabetic men from age 60 to 79. The PROSPER study found 772 cases of CVD and 287 of diabetes in a just over 3 years. The researchers found that in PROSPER patients without baseline CVD, metabolic syndrome was not linked to an increase in CVD, but there was over a four-fold increase in diabetes risk for patients with metabolic syndrome. These results were similar for patients with baseline CVD. Patients included in the BRHS study had 440 cases of CVD and 105 of diabetes over seven years. In this study, the researchers found a 27% increase in CVD risk and a seven-fold increase in diabetes risk for those with metabolic syndrome. The two studies demonstrated consensus in that body mass index or waist circumference, triglyceride levels, and glucose cutoff points did not seem to predict risk of CVD. However, the five criteria listed above were all associated risk of new diabetes onset.
“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,” write the authors. They agree that clinicians should focus on determining optimum and separate risk criteria for each disease that rather than having the same criteria used for both.
An accompanying comment written by Dr Richard Khan (American Diabetes Association, Alexandria, VA, USA) questions the usefulness of metabolic syndrome as a test for CVD risk. “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 pathogenises 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,” he concludes.
Can metabolic syndrome usefully predict cardiovascular disease and diabetes? Outcome data from two prospective studies
Naveed Sattar, Alex McConnachie, A Gerald Shaper, Gerard J Blauw, Brendan M Buckley, Anton J de Craen, Ian Ford, Nita G Forouhi, Dilys J Freeman, J Wouter Jukema, Lucy Lennon, Peter W Macfarlane, Michael B Murphy, Chris J Packard, David J Stott, Rudi G Westendorp, Peter H Whincup, James Shepherd, S Goya Wannamethee
The Lancet (2008).
DOI:10.1016/S0140-6736(08)60602-9
Written by: Peter M Crosta