Our results suggest that substantial proportions of phenotypic variance in CCA IMT and ICA IMT are attributable to shared genetic factors.

Objective-We examined whether B-mode ultrasound-detected carotid artery intima-media thickness (IMT) was elevated before the onset of clinical diabetes. Methods and Results-The study population for these analyses included 1127 nondiabetic participants, 66 prediabetic participants, and 303 diabetic participants with a mean age of 49.8 years who participated in the Mexico City Diabetes Study, a prospective cohort study. A lthough previous studies have established that coronary heart disease (CHD) risk factors are elevated before the clinical onset of diabetes 1-5 and a recent study has reported increased cardiovascular disease risk before the clinical onset of diabetes, 6 direct evidence of increased atherosclerosis before a clinical diagnosis of diabetes has not been documented. Documenting not only increased cardiovascular risk factors but increased atherosclerosis as well provides direct evidence that the atherosclerotic process is accelerated before the onset of clinical diabetes. Moreover, although type 2 diabetes is commonly considered a risk factor for CHD, treatment and control of hyperglycemia in type 2 diabetes have, at best, only a modest effect on reducing the risk of CHD associated with diabetes. 7 If the atherosclerotic process is accelerated before the onset of clinical diabetes, then preventing diabetes itself, either by altering lifestyle or pharmacologically, might be the optimum way to reduce the CHD risk associated with diabetes. See page 1715Recently, the Diabetes Prevention Program was one of several clinical trials to indicate that either through diet and exercise or with the aid of a pharmacologic agent it is possible to lower the incidence of diabetes among individuals at high risk for the disease. 8 -10 In short, there are lifestyle and pharmacologic interventions available that prevent diabetes. Hence, evidence suggesting that prediabetic individuals have not only elevated CHD risk factors but also elevated levels of subclinical atherosclerosis would indicate the importance of a lifestyle or pharmacologic intervention before the onset of clinical diabetes.Therefore, we examined (1) whether B-mode ultrasounddetected carotid artery intima-media thickness (IMT) was elevated in prediabetic individuals when compared with individuals who remained free of diabetes and (2) whether increased carotid artery IMT predicted incident diabetes. Methods The Mexico City Diabetes StudyThe Mexico City Diabetes Study is a population-based cohort of 2282 men and women first examined between 1990 and 1992 who were invited to return for 2 follow-up exams, the first conducted between 1993 and 1995 and the second from 1997 to 1999. 11 Participants were randomly selected from 6 low-income "colonias"

OBJECTIVE -Efficient detection of impaired glucose tolerance (IGT) is needed to implement type 2 diabetes prevention interventions. RESULTS -Among FOS, SAHS, and MCDS subjects, 24 -43% had MetS and 15-23% had IGT (including 2-5% with 2hPG Ն11.1 mmol/l). Among those with MetS, OR for IGT were 3-4, PPV were 0.24 -0.41, NPV were 0.84 -0.91, and PAR% were 30 -40%. Among subjects with MetS defined by impaired fasting glucose (IFG) and any two other traits, OR for IGT were 9 -24, PPV were 0.62-0.89, NPV were 0.78 -0.87, and PAR% were 3-12%. Among IRAS subjects, 24 -34% had MetS and 37-41% had IGT. Among those with MetS, ORs for IGT were 3-6, PPVs were 0.57-0.73, and NPVs were 0.67-0.72. In logistic regression models, IFG, large waist, and high triglycerides were independently associated with IGT (AROC 0.71-0.83) in all study populations. RESEARCH DESIGN AND METHODSCONCLUSIONS -The MetS, especially defined by IFG, large waist, and high triglycerides, efficiently identifies subjects likely to have IGT on OGTT and thus be eligible for diabetes prevention interventions. Diabetes Care 27:1417-1426, 2004T he prevalence of type 2 diabetes is rapidly growing worldwide, with rates expected to increase Ͼ165% by 2050 in the U.S. alone (1). Diabetes and its complications cause substantial loss in length and quality of life and incur Ͼ$132 billion annually in U.S. health care expenditures (2). There are few conditions with a more pernicious effect than diabetes on patient health and health care budgets.Fortunately, there is good experimental evidence that type 2 diabetes can be prevented or delayed. Lifestyle modification with diet and exercise, or use of metformin or acarbose, can reduce risk of type 2 diabetes in individuals with impaired glucose tolerance (IGT) by 30 -70% with ϳ7-14 affected people needing treatment for ϳ3 years to prevent one case of diabetes (3-6). Given that ϳ12 million U.S. adults may be eligible for these proven diabetes prevention interventions (7) and that they are effective, relatively safe, and feasible clinical and public health strategies, their broad implementation is now an urgent priority.An important impediment to wider translation of evidence-based diabetes prevention is the apparent need to identify people with IGT. IGT is defined using an oral glucose tolerance test (OGTT) as a plasma glucose level of 7.8 -11.0 mmol/l level 2 h after oral glucose challenge (2hPG) in individuals with nondiabetic fasting plasma glucose levels (Ͻ7.0 mmol/l) (8). Although fasting plasma glucose (FPG) in the "impaired" (IFG) range (6.1-6.9 mmol/l) is also a risk factor for type 2 diabetes, in many studies, IGT has been a stronger risk factor for diabetes than IFG (9 -12). Approximately 30 -

The causes for these differences in hypertension prevalence are not known but may reflect a less modernized lifestyle in Mexico City, including greater physical activity, less obesity, and the consumption of a high-carbohydrate, low-fat diet.

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