Middle-aged men with metabolic syndrome, which is characterized by insulin resistance and elevated blood glucose levels, obesity with increased abdominal fat, blood lipid abnormalities, and hypertension, are at increased risk for cardiovascular disease and death, according to an article in the December 4th issue of The Journal of the American Medical Association.

According to the National Cholesterol Education Program definition, roughly one third of middle-aged men and women in the United States have metabolic syndrome. Knowledge of the syndrome’s impact on cardiovascular and overall mortality in the general population is crucial for developing public health policy and clinical guidelines for its prevention and treatment. Despite its high prevalence, little is known of the prospective association of metabolic syndrome with cardiovascular and overall mortality.

Hanna-Maaria Lakka, M.D., Ph.D., and her American colleagues conducted a study to assess the association of metabolic syndrome with cardiovascular and overall mortality with use of recently proposed definitions. The Kuopio Ischaemic Heart Disease Risk Factory Study included 1,209 Finnish men aged 42 to 60 years at baseline (1984-1989) who were initially without cardiovascular disease, cancer, or diabetes. Follow-up continued through December 1998.

The researchers used four definitions of metabolic syndrome from the national Cholesterol Program and the World Health Organization, which consisted of measurements of various characteristics of the syndrome.

In this study population, the prevalence of the metabolic syndrome ranged from 8.8 percent to 14.3 percent depending on definition. There were 109 deaths during the approximately 11.4-year follow-up, with 46 due to cardiovascular disease and 27 due to coronary heart disease.

"Men with the metabolic syndrome as defined by the National Cholesterol Education Program were 2.9 to 4.2 times more likely and, as defined by the World Health Organization, 2.9 to 3.3 times more likely to die of coronary heart disease after adjustment for conventional cardiovascular risk factors. The metabolic syndrome as defined by the World Health Organization was associated with 2.6 to 3.0 times higher cardiovascular disease mortality and 1.9 to 2.1 times higher all-cause mortality," the researchers wrote. "Men with [measurements] on the metabolic factor in the highest quarter were 3.6, 3.2, and 2.3 times more likely to die of coronary heart disease, cardiovascular disease, and any cause, respectively."

"To our knowledge, this is the first prospective population-based cohort study reporting the association of the metabolic syndrome using recently proposed definitions with cardiovascular and overall mortality," the authors write. "The threat to public health posed by the metabolic syndrome will continue to grow as the metabolic syndrome becomes more common. Early identification, treatment, and prevention of the metabolic syndrome present a major challenge for physicians and public health policy makers facing an epidemic of overweight and sedentary lifestyle."

The metabolic syndrome as defined by the Education Program was the presence of three or more of the following: fasting plasma glucose of at least 110 mg/dL (6.1 mmol/L), serum triglycerides of at least 150 mg/dL (1.7 mmol/L), serum high-density lipoprotein cholesterol less than 40 mg/dL (1.04 mmol/L), blood pressure of at least 130/85 mm Hg, or waist girth of more than 102 cm (40 inches).

The metabolic syndrome for men according to the World Health Organization was defined as hyperinsulinemia or elevated fasting glycemia and at least two of the following: abdominal obesity, dyslipidemia, or hypertension. Insulin resistance was estimated as hyperinsulinemia based on fasting insulin levels in the upper fourth. Impaired fasting glycemia was defined as fasting blood glucose of 101-109 mg/dL (5.6-6.0 mmol/L). Diabetes was defined as blood glucose of at least 110 mg/dL (6.1 mmol/L) or a clinical diagnosis of diabetes with dietary, oral, or insulin treatment. Abdominal obesity was defined according to the original definition (waist-hip ratio greater than 0.90 or Body Mass Index equal or greater than 30) and the European Group for the Study of Insulin Resistance recommendation (waist girth equal or greater than 94 cm [37 inches]).