July 2003 - Men who have at least three metabolic abnormalities are at high risk of developing type 2 diabetes and heart disease, researchers report in a July 14th rapid access issue of Circulation: Journal of the American Heart Association.
Using a new, simplified definition of the "metabolic syndrome"� the clustering of certain metabolic-related heart disease risk factors � researchers predicted diabetes and coronary heart disease (CHD) at an early stage of disease development. This is noteworthy because early prediction might identify people who may benefit from aggressive lifestyle changes such as diet and exercise to delay or derail the disease process, says lead author Naveed Sattar, M.D., an honorary consultant in clinical biochemistry at the Glasgow Royal Infirmary in Scotland.
The new definition of the metabolic syndrome, also known as syndrome X, was developed by the U.S. National Cholesterol Education Panel (NCEP). It incorporates thresholds for five easily measured variables: abdominal obesity, elevated fasting blood triglycerides, low levels of HDL or "good" cholesterol, high fasting blood sugar (glucose) and high blood pressure. A person having any three of the five conditions would be classified as having the syndrome.
A previous definition by the World Health Organization required evidence of insulin resistance � the body's inability to use insulin efficiently � in people with normal glucose tolerance.
"This is a weakness because problems with glucose metabolism usually develop rather late in the syndrome. Glucose intolerance is usually the fourth or fifth condition to appear," Sattar says.
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Researchers knew that the metabolic syndrome predisposes people to CHD and diabetes, but little data existed on whether this simpler definition would be as predictive as the older, more stringent criteria.
"This is the first prospective study to show that the new criteria predict excess risk for both CHD and diabetes," he says. Researchers used data from 6,447 men in the West of Scotland Coronary Prevention Study (WOSCOPS) to test the NCEP's recently proposed definition. WOSCOPS is a primary prevention trial that proved the effectiveness of the cholesterol-lowering drug pravastatin for reducing heart disease death and disability. All the men participating in the trial had moderately elevated cholesterol levels. Sattar's group substituted body mass index figures collected in WOSCOPS for abdominal obesity.
Using the new definition, 26 percent of the men had the metabolic syndrome. They had 1.7 times the risk of a CHD event and 3.5 times the risk of developing diabetes during 4.9 years of follow-up, Sattar says. This level of risk was similar to an increase in age of 10 years, or to the risk in smokers.
The risk increased as the number of metabolic abnormalities rose. Men with four or five features of metabolic syndrome had 3.7 times the risk of coronary heart disease and 24.5 times the risk of diabetes compared to those with no abnormalities.
The diabetes finding is particularly striking because currently there are fewer predictive screening charts to identify people at high risk of becoming diabetic than there are for CHD, he says.
Interestingly, the cholesterol-lowering drug seemed equally beneficial for men with and without the metabolic syndrome. It reduced the risk of CHD by 27 percent in those with metabolic syndrome and 31 percent in those without it, he says.
Sattar's group also looked at another variable, the inflammatory marker C-reactive protein (CRP) that other studies have linked to the development of heart disease and diabetes. They found that CRP levels were higher in the men with the metabolic syndrome than in those without it.
Co-authors are Allan Gaw, M.D.; Olga Scherbakova; Ian Ford, Ph.D.; Denis St. J. O'Reilly, M.D.; Steven M. Haffner, M.D.; Chris Isles, M.D.; Peter W. Macfarlane, D.Sc.; Chris J. Packard, D.Sc.; Stuart M. Cobbe, M.D.; and James Shepherd, M.D.
Source: American Heart Association
