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The impact of metabolic syndrome on cardiovascular disease (CVD) risk can be lessened with cardiovascular fitness, researchers reported at the recent Scientific Sessions of the American Heart Association (AHA).
The study was one of several examining the effects of metabolic syndrome on the heart that were presented at the AHA meeting, held November 13–16 in Dallas.
Using the National Cholesterol Education Program (NCEP) Adult Treatment Panel III (ATP III) definition, metabolic syndrome typically is diagnosed when a person has at least three of this cluster of conditions: large waist circumference, elevated triglycerides, reduced HDL cholesterol, elevated blood pressure, and elevated fasting glucose.
The American Diabetes Association (ADA) and the European Association for the Study of Diabetes (EASD) issued a joint statement in September articulating concerns over whether the conditions actually comprise a syndrome, as they may have disparate pathologies1 (DOC News, October 2005). Syndromes, in the view of many, consist of a cluster of conditions with a common underlying pathology, ADA and EASD assert.
AHA has loosely adopted the ATP III definition (see sidebar, "AHA Metabolic Syndrome Recommendations"). At this year's meeting, the AHA communications office noted, "even as the precise definition of metabolic syndrome continues to be debated, evidence continues to mount that its presence signals an increased risk of cardiovascular disease and diabetes." Thus, several studies of metabolic syndrome were highlighted in a press briefing at the meeting.
PHYSICAL FITNESS SOFTENS CV EFFECT OF SYNDROME
Raul D. Santos, MD, of Albert Einstein Hospital of the University of Sao Paolo Medical School in Brazil, announced results of his fitness study, in which 23% of 449 men with no symptoms of heart disease had metabolic syndrome. Subjects underwent exercise stress testing and submitted blood samples.
The more markers of metabolic syndrome the patients had, the higher their white cell counts, indicating a greater presence of inflammation, Santos says.
However, when subjects were divided into three groups according to level of cardiorespiratory fitness, investigators found those who were fittest had no increase in white cells in the presence of metabolic risk factors. Patients with the lowest fitness level had a mean white cell count of 6.47 x 109 cells/l, while mean white cell count was 5.7 x 109 cells/l for those with the highest level of fitness.
In other words, the fittest subjects had a white cell count 8.5% lower than subjects with metabolic syndrome who were least fit.
"An increased level of physical fitness might exert its beneficial effect via attenuating inflammation in subjects with metabolic syndrome," Santos suggests.
Brisk walking for 30–40 minutes 5 days a week can achieve a moderate level of cardiorespiratory fitness, notes AHA President Robert H. Eckel, MD, of the University of Colorado Health Sciences Center in Denver.
PERIPHERAL VESSELS ALSO AT RISK
Jamal S. Rana, MD, PhD, of the University of Pittsburgh, reports that metabolic syndrome has adverse effects on the vasculature outside the heart. In a study of 1,698 subjects with familial hypercholesterolemia, 657 individuals, or 39%, met the ATP III definition of metabolic syndrome.
After adjusting for other cardiovascular risk factors, such as age and smoking, patients with familial hypercholesterolemia who met the definition of metabolic syndrome were twice as likely to have peripheral vascular disease as their counterparts who did not meet the definition.
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Rana notes that those with metabolic syndrome were 50% more likely to have CVD and 54% more likely to have coronary disease. Numbers linking metabolic syndrome to stroke were too small in this study to have statistical significance.
"Future studies need to be done to confirm our findings," Rana says. "There has been a paucity of data for the effect of metabolic syndrome specifically on cerebrovascular disease and peripheral vascular disease," compared with the data available linking metabolic syndrome with coronary heart disease.
METABOLIC SYNDROME IN AFRICAN AMERICANS, ELDERLY
Results from the Jackson Heart Study show that 37.2% of the 5,302 men and women in the population-based study of African Americans met the criteria for metabolic syndrome. By comparison, the overall prevalence of metabolic syndrome is around 25% for adults.
Of the five components comprising the syndrome, large waistline and high blood pressure were most prevalent, at 65.3% and 63.7%, respectively, says study director Herman Taylor Jr., MD, of the University of Mississippi at Jackson.
Taylor laid out four implications of his study: the need for education on the risk of the syndrome; the need for aggressive preventive efforts in African Americans, targeting obesity, hypertension, and LDL cholesterol; the need for increased exercise "as a mainstay of clinician counseling"; and the need for diets that lower blood pressure and limit calories.
Finally, a study of the elderly shows that those with metabolic syndrome have more adverse cardiovascular events than their counterparts without the syndrome. Lead investigator of this phase of the Health ABC study, Javed Butler, MD, assistant professor of medicine at Vanderbilt University Medical Center in Nashville, Tenn., points out that adverse events associated with the metabolic syndrome are well documented in younger subjects, but that there has been a lack of data on its effects in the elderly.
The study consisted of 3,035 subjects aged 
70 years. Of these, 38% met
the criteria for metabolic syndrome, a somewhat higher prevalence than in the
population as a whole.
The number of all-cause hospitalizations was significantly higher in the group with metabolic syndrome, and there was a "strong trend" toward higher coronary mortality in the group with the syndrome. These findings show that metabolic syndrome continues to pose a risk with advancing age, Butler says.
Eckel acknowledges that the definition of metabolic syndrome "may need refining."
"It is an evolving concept at this point," he tells DOC
News. "Our purpose is to draw attention to risk beyond high LDL.
The ADA position that the separate parts [of the syndrome] should be
considered is well received." 
AHA Metabolic Syndrome Recommendations
The American Heart Association (AHA) and the National Heart, Lung, and Blood Institute recommend that metabolic syndrome be identified as the presence of three or more of these risk factors:
40 in (102 cm) for men; 35 in (88 cm)
for women. 150 mg/dl. 130/85 mmHg. 100 mg/dl. AHA recommends reducing the risk for cardiovascular disease (CVD) and type 2 diabetes as the primary goal of clinical management of metabolic syndrome. The first-line therapy is to address the major risk factors for CVD: stop smoking and reduce LDL cholesterol, blood pressure, and glucose levels to the recommended levels.
The following lifestyle therapies also are recommended as first-line interventions to reduce metabolic syndrome risk factors:
Source: AHA, www.americanheart.org/presenter.jhtml?identifier=4756
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