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Watch out, "metabolic syndrome," there's a new term on thescene to describe a certain group of cardiovascular disease (CVD) dangers. Atleast that's the aim of the American Diabetes Association (ADA) as it beginspromoting the concept of "cardiometabolic risk."
ADA's Cardiometabolic Risk Initiative (CMRI) is a national effort similarto its Make the Link! educational program that stresses the associationbetween diabetes, heart disease, and stroke. CMRI encourages physicians andthe public to adopt cardiometabolic risk (CMR) as an umbrella term that willhelp them better understand and manage all cardiovascular and diabetes riskfactors.
ADA hopes to replace the term metabolic syndrome, which is controversialyet becoming a more common part of medical parlance, with CMR, which theassociation deems a "more useful and evidence-based paradigm to helppatients achieve better health outcomes."
"The idea of metabolic syndrome as a cluster of variables—suchas obesity, hypertension, low HDL, high triglycerides, and impaired fastingplasma glucose—whose presence increases a person's risk ofcardiovascular disease has attracted great interest but also raised manyquestions and controversy," says David Eddy, MD, PhD, medical directorof Archimedes, Inc.
ADA partnered with Archimedes last summer to build Diabetes PHD, a riskcalculator that simulates the biology underlying diabetes as well as factorssuch as comorbidity risks, medications, and treatments (DOC News,July 2005).
ADA now has asked Eddy and his team to use the Archimedes model to developthe CMR Calculator, a new, interactive tool that by the end of the year willbe available to help physicians evaluate the potential impact of variablesrelated to CVD risk. Archimedes already includes factors such as body massindex (BMI), waist circumference ratio, fasting plasma glucose, bloodpressure, HDL, and triglycerides, as well as age, sex, race/ethnicity, familyhistory, tobacco use, LDL, apolipoprotein B, and C-reactive protein.Simulations of new clinical trials and epidemiological and cohort studies areused to validate the model and compare predictions withresults.
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INSULIN RESISTANCE THE UNDERLYING CAUSE
The ADA initiative is supported in part by recent fi ndings from theCenters for Disease Control and Prevention (CDC) that link obesity anddiabetes prevalence and show the association of pre-diabetes, or impairedfasting glucose (IFG), where blood glucose levels are 100–125 mg/dl,with a higher prevalence of CVD risk factors such as obesity, hypertension,and dyslipidemias. The studies were presented at ADA's 66th Annual Scientifi cSessions held June 9–13 in Washington, D.C.
K.M. Venkat Narayan, MD, chief of epidemiology and statistics in CDC'sDivision of Diabetes Translation, discussed a study that used data from theNational Health Interview Survey and a statistical model to track the effectof BMI on diabetes risk. The study found the lifetime risk for developingdiabetes for normal-weight 18-year-old males is 20%, compared with 30% foroverweight males, 57% for obese males, and 70% for very obese males. The risksfor 18-year-old females are 17%, 35%, 55%, and 74%, respectively, for the fourBMI categories.
Desmond E. Williams, MD, PhD, a CDC medical epidemiologist, used1999–2002 National Health and Nutrition Examination Survey data for agroup of 3,030 adults aged 20–75 years without diagnosed diabetes. Hefound 28% of the group had pre-diabetes or IFG as well as a signifi cantlyhigher prevalence of CVD risk factors, including obesity, hypertension, anddyslipidemias.
Insulin resistance is the core problem with all of these risks, accordingto Eddy. "Our analysis indicates that the cluster of variablesassociated with the metabolic syndrome, as it has been defi ned by variousorganizations, is well explained by insulin resistance as an underlyingcause," Eddy says. Insulin resistance is responsible for more than 40%of heart attacks, according to Archimedes calculations.
Indeed, the role of insulin resistance in metabolic syndrome (also called"syndrome X" and "insulin-resistance syndrome"), hasbeen recognized since the syndrome was described in 1988 by Gerald M. Reaven,MD.1 Just lastDecember, at the annual meeting of the American Public Health Association inPhiladelphia, Reaven gave a talk entitled, "Insulin Resistance VersusMetabolic Syndrome: Different Names, Different Concepts, DifferentGoals," in which he emphasized his conclusion that "insulinresistance explains the clustering of the components that make up themetabolic syndrome."
The ability of insulin to transport glucose varies more than 600% in thepopulation at large, Reaven says. The one-third of people with the mostinsulin resistance are sufficiently insulin resistant as to be at greatlyincreased risk to develop a number of abnormalities and clinicalsyndromes.
"Is there a utility in making a diagnosis of metabolic syndrome? It'sobvious from my tone, I don't think so," Reaven says. "We shouldunderstand the pathophysiological process and appearance of any risk factorand should check for others. All factors should be identifi ed andtreated."
Eddy says it makes sense to redefine what's been called the metabolicsyndrome as the insulin-resistance syndrome.
"With more than half of the U.S. population destined to developinsulin resistance at least to some degree, the search for better ways toidentify people who have it is gaining importance," Eddy says.
Footnotes
More information about cardiometabolic risk is available from ADA atwww.diabetes.org/weightloss-and-exercise/diabetes-metabolic-health.jsp.
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