Peter J. Savage

Diagnosis and Management of the Metabolic Syndrome: An American Heart Association/National Heart, Lung, and Blood Institute Scientific Statement

The metabolic syndrome has received increased attention in the past few years. This statement from the American Heart Association (AHA) and the National Heart, Lung, and Blood Institute (NHLBI) is intended to provide up-to-date guidance for professionals on the diagnosis and management of the metabolic syndrome in adults. The metabolic syndrome is a constellation of interrelated risk factors of metabolic origin— metabolic risk factors —that appear to directly promote the development of atherosclerotic cardiovascular disease (ASCVD).1 Patients with the metabolic syndrome also are at increased risk for developing type 2 diabetes mellitus. Another set of conditions, the underlying risk factors , give rise to the metabolic risk factors. In the past few years, several expert groups have attempted to set forth simple diagnostic criteria to be used in clinical practice to identify patients who manifest the multiple components of the metabolic syndrome. These criteria have varied somewhat in specific elements, but in general they include a combination of both underlying and metabolic risk factors. The most widely recognized of the metabolic risk factors are atherogenic dyslipidemia, elevated blood pressure, and elevated plasma glucose. Individuals with these characteristics commonly manifest a prothrombotic state and a pro-inflammatory state as well. Atherogenic dyslipidemia consists of an aggregation of lipoprotein abnormalities including elevated serum triglyceride and apolipoprotein B (apoB), increased small LDL particles, and a reduced level of HDL cholesterol (HDL-C). The metabolic syndrome is often referred to as if it were a discrete entity with a single cause. Available data suggest that it truly is a syndrome, ie, a grouping of ASCVD risk factors, but one that probably has more than one cause. Regardless of cause, the syndrome identifies individuals at an elevated risk for ASCVD. The magnitude of the increased risk can vary according to which components of the syndrome are …

CARDIA: study design, recruitment, and some characteristics of the examined subjects.

In 1984, a prospective cohort study, Coronary Artery Risk Development in Young Adults (CARDIA) was initiated to investigate life-style and other factors that influence, favorably and unfavorably, the evolution of coronary heart disease risk factors during young adulthood. After a year of planning and protocol development, 5,116 black and white women and men, age 18-30 years, were recruited and examined in four urban areas: Birmingham, Alabama; Chicago, Illinois; Minneapolis, Minnesota, and Oakland, California. The initial examination included carefully standardized measurements of major risk factors as well as assessments of psychosocial, dietary, and exercise-related characteristics that might influence them, or that might be independent risk factors. This report presents the recruitment and examination methods as well as the mean levels of blood pressure, total plasma cholesterol, height, weight and body mass index, and the prevalence of cigarette smoking by age, sex, race and educational level. Compared to recent national samples, smoking is less prevalent in CARDIA participants, and weight tends to be greater. Cholesterol levels are representative and somewhat lower blood pressures in CARDIA are probably, at least in part, due to differences in measurement methods. Especially noteworthy among several differences in risk factor levels by demographic subgroup, were a higher body mass index among black than white women and much higher prevalence of cigarette smoking among persons with no more than a high school education than among those with more education.

Markers of inflammation and prediction of diabetes mellitus in adults (Atherosclerosis Risk in Communities study): a cohort study

BACKGROUND Type 2 diabetes mellitus and atherosclerotic cardiovascular disease have common antecedents. Since markers of inflammation predict coronary heart disease and are raised in patients with type 2 diabetes, we investigated whether they predict whether people will develop type 2 diabetes. METHODS 12,330 men and women, aged 45-64 years, were followed up for a mean of 7 years. We analysed the association between different markers of acute inflammation and subsequent diagnosis of diabetes. In a subgroup of 610 individuals selected originally for an unrelated atherosclerosis case-control study, we also investigated diabetes associations with total sialic acid and orosomucoid, haptoglobin, and alpha1-antitrypsin. FINDINGS 1335 individuals had a new diagnosis of diabetes. Adjusted odds ratios for developing diabetes for quartile extremes were 1.9 (95% CI 1.6-2.3) for raised white-cell count, 1.3 (1.0-1.5) for low serum albumin, and 1.2 (1.0-1.5) for raised fibrinogen. In the subgroup analysis, individuals with concentrations of orosomucoid and sialic acid of more than the median had odds ratios of 7.9 (2.6-23.7) and 3.7 (1.4-9.8), respectively. Adjustment for body-mass index and waist-to-hip ratio lessened the associations; those for white-cell count (1.5 [1.3-1.8]), orosomucoid (7.1 [2.1-23.7]), and sialic acid (2.8 [1.0-8.1]) remained significant. INTERPRETATION Markers of inflammation are associated with the development of diabetes in middle-aged adults. Although autoimmunity may partly explain these associations, they probably reflect the pathogenesis of type 2 diabetes.

Insulin Sensitivity and Atherosclerosis

Background Reduced insulin sensitivity has been proposed as an important risk factor in the development of atherosclerosis. However, insulin sensitivity is related to many other cardiovascular risk factors, including plasma insulin levels, and it is unclear whether an independent role of insulin sensitivity exists. Large epidemiological studies that measure insulin sensitivity directly have not been conducted. Methods and Results The Insulin Resistance Atherosclerosis Study (IRAS) evaluated insulin sensitivity (SI) by the frequently sampled intravenous glucose tolerance test with analysis by the minimal model of Bergman. IRAS measured intimal-medial thickness (IMT) of the carotid artery as an index of atherosclerosis by use of noninvasive B-mode ultrasonography. These measures, as well as factors that may potentially confound or mediate the relationship between insulin sensitivity and atherosclerosis, were available in relation to 398 black, 457 Hispanic, and 542 non-Hispanic white IRAS participants. Ther...

The association between symptomatic, severe hypoglycaemia and mortality in type 2 diabetes: retrospective epidemiological analysis of the ACCORD study

Objective To determine whether there is a link between hypoglycaemia and mortality among participants in the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial. Design Retrospective epidemiological analysis of data from the ACCORD trial. Setting Diabetes clinics, research clinics, and primary care clinics. Participants Patients were eligible for the ACCORD study if they had type 2 diabetes, a glycated haemoglobin (haemoglobin A1C) concentration of 7.5% or more during screening, and were aged 40-79 years with established cardiovascular disease or 55-79 years with evidence of subclinical disease or two additional cardiovascular risk factors. Intervention Intensive (haemoglobin A1C <6.0%) or standard (haemoglobin A1C 7.0-7.9%) glucose control. Outcome measures Symptomatic, severe hypoglycaemia, manifest as either blood glucose concentration of less than 2.8 mmol/l (<50 mg/dl) or symptoms that resolved with treatment and that required either the assistance of another person or medical assistance, and all cause and cause specific mortality, including a specific assessment for involvement of hypoglycaemia. Results 10 194 of the 10 251 participants enrolled in the ACCORD study who had at least one assessment for hypoglycaemia during regular follow-up for vital status were included in this analysis. Unadjusted annual mortality among patients in the intensive glucose control arm was 2.8% in those who had one or more episodes of hypoglycaemia requiring any assistance compared with 1.2% for those with no episodes (53 deaths per 1924 person years and 201 deaths per 16 315 person years, respectively; adjusted hazard ratio (HR) 1.41, 95% CI 1.03 to 1.93). A similar pattern was seen among participants in the standard glucose control arm (3.7% (21 deaths per 564 person years) v 1.0% (176 deaths per 17 297 person years); adjusted HR 2.30, 95% CI 1.46 to 3.65). On the other hand, among participants with at least one hypoglycaemic episode requiring any assistance, a non-significantly lower risk of death was seen in those in the intensive arm compared with those in the standard arm (adjusted HR 0.74, 95% 0.46 to 1.23). A significantly lower risk was observed in the intensive arm compared with the standard arm in participants who had experienced at least one hypoglycaemic episode requiring medical assistance (adjusted HR 0.55, 95% CI 0.31 to 0.99). Of the 451 deaths that occurred in ACCORD up to the time when the intensive treatment arm was closed, one death was adjudicated as definitely related to hypoglycaemia. Conclusion Symptomatic, severe hypoglycaemia was associated with an increased risk of death within each study arm. However, among participants who experienced at least one episode of hypoglycaemia, the risk of death was lower in such participants in the intensive arm than in the standard arm. Symptomatic, severe hypoglycaemia does not appear to account for the difference in mortality between the two study arms up to the time when the ACCORD intensive glycaemia arm was discontinued. Trial registration NCT00000620.

Increasing cardiovascular disease burden due to diabetes mellitus: the Framingham Heart Study.

Background— Marked reductions in cardiovascular disease (CVD) morbidity and mortality have occurred in the United States over the last 50 years. We tested the hypothesis that the relative burden of CVD attributable to diabetes mellitus (DM) has increased over the past 5 decades. Methods and Results— Participants aged 45 to 64 years from the Framingham Heart Study, who attended examinations in an “early” time period (1952 to 1974), were compared with those who attended examinations in a later time period (1975 to 1998). The risk of CVD events (n=133 among those with and 1093 among those without DM) attributable to DM in the 2 time periods was assessed with Cox proportional hazards models; population attributable risk of DM as a CVD risk factor was calculated for each time period. The age- and sex-adjusted hazard ratio for DM as a CVD risk factor was 3.0 (95% CI, 2.3 to 3.9) in the earlier time period and 2.5 (95% CI, 1.9 to 3.2) in the later time period. The population attributable risk for DM as a CVD risk factor increased from 5.4% (95% CI, 3.8% to 6.9%) in the earlier time period to 8.7% (95% CI, 5.9% to 11.4%) in the later time period (P for attributable risk ratio=0.04), although multivariable adjustment resulted in attenuation of these findings (P=0.12); most of these observations were found among men. Conclusions— The proportion of CVD attributable to DM has increased over the past 50 years in Framingham. These findings emphasize the need for increased efforts to prevent DM and to aggressively treat and control CVD risk factors among those with DM.

The Insulin Resistance Atherosclerosis Study (IRAS). Objectives, design, and recruitment results

The Insulin Resistance Atherosclerosis Study (IRAS) is the first epidemiologic study designed to assess the relationships between insulin resistance, insulinemia, glycemia, other components of the insulin resistance syndrome, and prevalent cardiovascular disease (CVD) in a large multiethnic cohort. Over 1600 men and women were recruited from four geographic areas to represent a range of glucose tolerance (normal, impaired, and diabetic) and ethnicity (hispanic, non-Hispanic white, and African-American). Insulin resistance was assessed directly using the frequently sampled intravenous glucose tolerance test with minimal model analysis. Intimal-medial carotid artery wall thickness, an indicator of atherosclerosis, was measured using B-mode ultrasonography. Prevalent CVD was assessed by questionnaire and resting electrocardiography. This report describes the design of the study and provides the recruitment results. Forthcoming cross-sectional analyses will help to disentangle the association between insulin resistance and CVD, apart from the concomitant hyperinsulinemia and related CVD risk factors.

Increased Insulin Resistance and Insulin Secretion in Nondiabetic African-Americans and Hispanics Compared With Non-Hispanic Whites: The Insulin Resistance Atherosclerosis Study

The etiology of NIDDM is still controversial, with both insulin resistance and decreased insulin secretion postulated as potential important factors. African-Americans and Hispanics have a two- to threefold excess risk of developing NIDDM compared with non-Hispanic whites. Yet little is known concerning the prevalence of insulin resistance and secretion defects in minorities, especially in African-Americans in population-based studies. Fasting and 2-h post–glucose load glucose and insulin levels, insulin-mediated glucose disposal (insulin sensitivity index) (SI), glucose effectiveness (SG), and first-phase insulin response (acute insulin response [AIR]) were determined in nondiabetic African-Americans (n = 288), Hispanics (n = 363), and non-Hispanic whites (n = 435) as part of the Insulin Resistance Atherosclerosis Study. Subjects received a standard 2-h oral glucose tolerance test on the first day and an insulin-modified frequently sampled intravenous glucose tolerance test on the second day. African-Americans and Hispanics were more obese than non-Hispanic whites. Both African-Americans and Hispanics had higher fasting and 2-h insulin concentrations and AIR but lower SI than non-Hispanic whites. No ethnic difference was observed in SG. After further adjustments for obesity, body fat distribution, and behavioral factors, African-Americans continued to have higher fasting and 2-h insulin levels and AIR, but lower SI, than non-Hispanic whites. In contrast, after adjustment for these covariates, no significant ethnic differences in SI or fasting insulin levels were observed between Hispanics and non-Hispanic whites. Hispanics continued to havehigher 2-h insulin levels and AIRs than those in non-Hispanic whites. In this report, the association between SI and upper body adiposity (waist-to-hip ratio) was similar in each ethnic group. Both nondiabetic African-Americans and Hispanics have increased insulin resistance and higher AIR than nondiabetic non-Hispanic whites, suggesting that greater insulin resistance may be in large part responsible for the higher prevalence of NIDDM in these minority groups. However, in Hispanics, the greater insulin resistance may be due to greater adiposity and other behavioral factors.

Trends in All-Cause and Cardiovascular Disease Mortality Among Women and Men With and Without Diabetes Mellitus in the Framingham Heart Study, 1950 to 2005

Background— Despite population declines in all-cause mortality, women with diabetes mellitus may have experienced an increase in mortality rates compared with men. Methods and Results— We examined change in all-cause, cardiovascular, and non–cardiovascular disease mortality rates among Framingham Heart Study participants who attended examinations during an “earlier” (1950 to 1975; n=930 deaths) and a “later” (1976 to 2001; n=773 deaths) time period. Diabetes mellitus was defined as casual glucose ≥200 mg/dL, fasting plasma glucose ≥126 mg/dL, or treatment. Among women, the hazard ratios (HRs) for all-cause mortality in the later versus the earlier time period were 0.59 (95% confidence interval, 0.50 to 0.70; P<0.0001) for those without diabetes mellitus and 0.48 (95% confidence interval, 0.32 to 0.71; P=0.002) for those with diabetes mellitus. Similar results were observed in men. Among women and men, the HR of cardiovascular disease mortality declined among those with and without diabetes mellitus. Non–cardiovascular disease mortality declined among women without diabetes mellitus (HR, 0.76; P=0.01), whereas no change was observed among women with diabetes mellitus or among men with or without diabetes mellitus. Individuals with versus those without diabetes mellitus were at increased risk of all-cause mortality in the earlier (HR, 2.44; P<0.0001) and later (HR, 1.95; P<0.0001) time periods. Conclusions— Reductions in all-cause mortality among women and men with diabetes mellitus have occurred over time. However, mortality rates among individuals with diabetes mellitus remain ≈2-fold higher compared with individuals without diabetes mellitus.

Thickening of the Carotid Wall: A Marker for Atherosclerosis in the Elderly?

BACKGROUND AND PURPOSE We investigated the relationships between prevalent coronary heart disease (CHD), clinically manifest atherosclerotic disease (ASD), and major established risk factors for atherosclerosis and intima-media thickness (IMT) in the common carotid arteries (CCA) and internal carotid arteries (ICA) separately and in combination in older adults. We wished to determine whether a noninvasive measurement can serve as an indicator of clinically manifest atherosclerotic disease and to determine which of the two variables, CCA IMT or ICA IMT, is a better correlate. METHODS IMT of the CCA and ICA was measured with duplex ultrasound in 5117 of 5201 individuals enrolled in the Cardiovascular Health Study, a study of the risk factors and the natural history of cardiovascular disease in adults aged 65 years or more. Histories of CHD, peripheral arterial disease, and cerebrovascular disease were obtained during baseline examination. Risk factors included cholesterol levels, cigarette smoking, elevated blood pressure, diabetes, age, and sex. Relationships between risk factors and IMT were studied by multiple regression analysis and canonical variate analysis. Prediction of prevalent CHD and ASD by IMT measurements in CCAs and ICAs were made by logistic regression, adjusting for age and sex. RESULTS IMT measurements of the CCAs and ICAs were greater in persons with CHD and ASD than those without, even after controlling for sex (P < .001). IMT measurements in the ICA were greater than those in the CCA. Risk factors for ASD accounted for 17% and 18% of the variability in IMT in the CCA and ICA, respectively. These same risk factors accounted for 25% of the variability of a composite measurement consisting of the sum of the ICA IMT and CCA IMT. The ability to predict CHD and ASD was greater for ICA IMT (odds ratio [confidence interval]: 1.36 [1.31 to 1.41] and 1.35 [1.25 to 1.44], respectively) than for CCA IMT (1.09 [1.05 to 1.13] and 1.17 [1.09 to 1.25]). CONCLUSIONS Whereas CCA IMT is associated with major risk factors for atherosclerosis and existing CHD and ASD in older adults, this association is not as strong as that for ICA IMT. The combination of these measures relates more strongly to existing CHD and ASD and cerebrovascular disease risk factors than either taken alone.