Association of A1C With Cardiovascular Disease and Metabolic Syndrome in Asian Indians With Normal Glucose Tolerance

Abstract

OBJECTIVE -This study examines the association of A1C with cardiovascular disease (CVD) risk factors, coronary artery disease (CAD), and metabolic syndrome in Asian Indians with normal glucose tolerance (NGT). RESEARCH DESIGN AND METHODS-This cross-sectional study recruited subjects from phase III of the Chennai Urban Rural Epidemiology Study (CURES), an epidemiological study in a representative population of Chennai (formerly Madras) in South India, conducted between January 2003 and June 2004. Included were 1,644 subjects with NGT, i.e., fasting plasma glucose Ͻ100 mg/dl (5.6 mmol/l) and 2-h postload plasma glucose Ͻ140 mg/dl (7.8 mmol/l). A1C was measured using the Biorad Variant machine. Metabolic syndrome was defined based on modified Adult Treatment Panel III guidelines.RESULTS -The mean Ϯ SD A1C value in the study cohort was 5.5 Ϯ 0.4%. A1C showed a significant association with BMI (␤ ϭ 0.017, P Ͻ 0.001), systolic (␤ ϭ 0.002, P ϭ 0.028) and diastolic (␤ ϭ 0.202, P ϭ 0.017) blood pressure, waist circumference (␤ ϭ 0.007, P Ͻ 0.001), serum cholesterol (␤ ϭ 0.002, P Ͻ 0.001), triglycerides (␤ ϭ 0.001, P Ͻ 0.001), LDL cholesterol (␤ ϭ 0.002, P Ͻ 0.001), fasting insulin (␤ ϭ 0.009, P Ͻ 0.001), and homeostasis model assessment of insulin resistance (␤ ϭ 0.047, P Ͻ 0.001) after adjusting for age and sex. Regression analysis showed that A1C had a strong association with metabolic syndrome that persisted after adjusting for age and sex (odds ratio [OR] 2.9 [95% CI 2.08 -4.00]; P Ͻ 0.001). A1C also had a strong association with CAD (2.6 [1.23-5.63]; P ϭ 0.01), but the significance was lost when adjusted for age and sex.CONCLUSIONS -There is a strong association of A1C with prevalent CVD risk factors in Asian-Indian subjects with NGT. Diabetes Care 30:1527-1532, 2007T he DCCT (Diabetes Control and Complications Trial) and UKPDS (UK Prospective Diabetes Study) demonstrated the importance of A1C in the development of long-term diabetes microvascular complications (1,2). Further, both studies elegantly demonstrated significant reductions in the risk of developing microvascular complications for every percentage of reduction in A1C levels (1,2). However, the association of A1C with cardiovascular disease (CVD) is less clear (3)(4)(5)(6)(7)(8).CVD is the principal cause of mortality globally, particularly in type 2 diabetic subjects, as their CVD mortality risk is equal to that of subjects without diabetes who had a previous episode of myocardial infarction (9). Recent prospective studies have shown that A1C is associated with CVD and mortality (10). This association has also recently been extended to nondiabetic subjects, as the relationship of CVD with glycemia is believed to be a continuum without a threshold effect (5-8).However, there is uncertainty as to the nature of the relationship, as some studies report no statistically significant association (3) between A1C and CVD in nondiabetic males while others do (4 -8).Asian Indians are known to have very high rates of premature coronary artery disease (CAD) and diab...

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