REGARDS has been described previously.31
The cohort, by design, is 42% African American, and 55% female. Because the primary goals of REGARDS are to elucidate regional and racial differences in stroke, the Stroke Belt, located in the southeastern US, was over-sampled such that 20% of the overall cohort was selected from the “buckle” of the Stroke Belt (the coastal plain region of North Carolina, South Carolina, and Georgia); 30% from the rest of the Stroke Belt (the remaining parts of North Carolina, South Carolina, and Georgia plus Alabama, Mississippi, Louisiana, Arkansas, and Tennessee); and 50% from the remaining 40 contiguous states. Individuals identified by commercially available lists were contacted by mail and telephone. Upon enrollment, individuals underwent a computer assisted telephone interview followed by an in-home examination. During the telephone interview, demographic and self-reported medical information was obtained. During the in-home examination, the participant's blood pressure was measured, an electrocardiogram was performed, and blood and urine samples were obtained.
As of June 2007, REGARDS had recruited 28,224 participants. Of these, we included the 22,719 participants (80%) with complete data for MetSyn components. Of the 5,505 individuals excluded from this analysis, 4,118 were excluded for not fasting at the time of phlebotomy or because their fasting status was unknown; 1,378 for missing data on a component of the MetSyn; and 9 for missing data on race or gender. Individuals excluded were of similar age (66 vs. 65 years) and gender (55% vs. 55% female) as those included. Individuals excluded were less likely to be from the stroke buckle (16%) than the stroke belt (21%) or non-belt (20%) and were more likely to be African American (23%) than white (17%).
Individuals meeting any 3 of the following criteria were classified as having ATP-III MetSyn: elevated waist circumference (>40 inches in men or >35 inches in women), hypertriglyceridemia (≥150 mg/dL), decreased high density lipoprotein-cholesterol (HDL-C) (<40 mg/dL in men or <50 mg/dL in women), elevated blood pressure (systolic blood pressure ≥130 mmHg, diastolic blood pressure ≥85 mmHg, history of hypertension, or use of medications for elevated blood pressure), or hyperglycemia (fasting glucose ≥100 mg/dL, history of diabetes, or use of medications for diabetes). To meet IDF criteria, individuals had to have an elevated waist circumference (≥37 inches in men or ≥31.5 inches in women) and 2 of the other 4 ATP-III criteria. Using these criteria, we classified participants into 1 of the following 4 groups: (1) no MetSyn, (2) MetSyn by both ATP-III and IDF criteria, (3) MetSyn by only ATP-III criteria, or (4) MetSyn by only IDF criteria.
We assessed the association between MetSyn classification and prevalent CVD among all 22,719 participants. CVD was defined as a self-reported history of any of the following: myocardial infarction, percutaneous coronary intervention, coronary artery bypass graft surgery, stroke, transient ischemic attack, carotid endarterectomy, carotid stenting, or surgery for peripheral arterial disease or abdominal aortic aneurysm. We performed multivariable logistic regression to determine the odds of self-reported CVD for each of the MetSyn classifications, incrementally controlling for demographic variables (age, race, gender, and geographic region), education and income, and behavioral risk factors (smoking status, alcohol use, and physical activity). Because the MetSyn includes individuals with and without diabetes, we performed these analyses in all participants (including those with and without diabetes) and separately in those without diabetes.
In order to compare the estimated future CHD risk of participants in each of the 4 MetSyn classifications, we calculated 10-year FRS for CHD death or myocardial infarction.32
This risk calculator considers diabetes a risk factor for coronary artery disease, but not a risk equivalent as defined by ATP-III.4
Therefore, we also calculated these FRS assuming that all diabetic participants had a FRS >20%. We then performed multivariable logistic regression to determine the odds of having a FRS >20% for each of the MetSyn classifications, controlling for demographic variables (age, race, gender, and geographic region), education and income, and behavioral risk factors (smoking status, alcohol use, and physical activity). We chose to perform separate models with and without adjustment for age and smoking as they are part of the FRS but not part of the MetSyn definition. This allowed us to assess the impact that MetSyn components have on the FRS. For this portion of the analysis, we excluded the 3,102 participants with a self-reported history of CHD (myocardial infarction, percutaneous coronary intervention, or coronary artery bypass graft surgery) and an additional 1,884 participants with evidence of myocardial infarction on their enrollment electrocardiogram who did not report a history of CHD. An additional 63 participants were missing data on other components of the FRS. Therefore, of the 22,719 participants, a total of 17,670 (78%) were included in these models.
REGARDS is supported by a cooperative agreement U01 NS041588 from the National Institute of Neurological Disorders and Stroke, NIH, Department of Health and Human Service. During a portion of this work, Dr. Brown was supported in part by grant 5 T32 HS013852 from the Agency for Healthcare Research and Quality. Dr. Brown is currently supported by grant number KL2 RR025776 from the NIH National Center for Research Resources. Drs. Safford and Bittner were supported by NHLBI R01 HL80477-01A1. The authors are solely responsible for the design and conduct of this study, all study analyses, the drafting and editing of the paper, and its final contents.