Metabolic syndrome, which is also known as insulin resistance syndrome, is characterized by insulin resistance and elevated blood sugar levels, obesity marked by a pot belly, abnormal blood lipids, and high blood pressure. According to the study authors, metabolic syndrome is likely caused by some combination of obesity, a sedentary lifestyle, diet and genetic factors.
Given the worldwide epidemic of obesity, the syndrome represents a serious public health issue.
The report appears in tomorrow's issue of the Journal of the American Medical Association.
One problem in assessing the prevalence and severity of metabolic syndrome is that there has been no consistent definition as to what exactly it is. To help ameliorate this, the National Cholesterol Education Program (NCEP) and the World Health Organization (WHO) recently published definitions that are for the most part similar but vary in their particulars.
Four of these definitions were used in this study, which looked at men involved in the Kuopio Ischaemic Heart Disease Risk Factor Study in Finland. The 1,209 men, all Finnish, were 42 to 60 years old at the beginning of the study and were followed for about 11 years. None of the men with metabolic syndrome had cardiovascular disease or diabetes when the study commenced.
Depending on the definition used, the prevalence of metabolic syndrome in the sample population was 8.8 percent to 14.3 percent.
Men with metabolic syndrome as defined by the NCEP were 2.9 to 4.2 times more likely to die of coronary heart disease than healthy men. Those with metabolic syndrome as defined by the WHO were 2.9 to 3.3 times more likely to die of coronary heart disease, after adjusting for other factors.
Mortality from cardiovascular disease was 2.6 to 3 times higher among men with metabolic syndrome as defined by the WHO. Death from any cause was 1.9 to 2.1 times higher in this group. The NCEP definition was less helpful in predicting death from cardiovascular disease and other causes.
This is grim news for the United States, in particular, where, according to the NCEP definition, about one-third of middle-aged men and women have the syndrome. The CDC has estimated that up to 47 million Americans may suffer from metabolic syndrome.
Certain characteristics of metabolic syndrome, including high blood pressure and elevated cholesterol, are known to be risk factors for heart disease, says Dr. Daniel Fisher, a cardiologist with New York University Medical Center in New York City. Abdominal obesity and insulin resistance may be risk factors, but are less clear-cut.
"Doctors treat individual risk factors and don't necessarily put a label on it," Fisher says. "Putting the label may help to raise awareness that risk of heart disease is raised in these people."
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