C-Reactive Protein and Glycemic Control in Adults With Diabetes

Abstract

OBJECTIVE—Recent evidence suggests that poor glycemic control is significantly associated with the development of macrovascular complications of diabetes. Studies have indicated that C-reactive protein (CRP) is an important risk factor for cardiovascular disease. The purpose of this study was to determine the relation between CRP and HbA1c in a large national sample of individuals with diabetes. RESEARCH DESIGN AND METHODS—A nationally representative sample of noninstitutionalized U.S. adults aged 17 years and over with nongestational diabetes was derived from the National Health and Nutrition Examination Survey III (1988–1994) (n = 1,018). Respondents with diabetes were stratified by HbA1c level. The main outcome measure was elevated (>0.30 mg/dl) CRP. RESULTS—In unadjusted analyses, respondents with diabetes who had elevated HbA1c levels (≥9.0%) had a significantly higher percent of elevated CRP than people with low (<7%) HbA1c levels (P < 0.001). In adjusted regression analysis, after controlling for age, race, sex, smoking, length of time with diabetes, insulin, and BMI, HbA1c was significantly associated with an increased likelihood of elevated CRP for HbA1c >9.0% (OR 2.15, 95% CI 1.07–4.32) and for HbA1c >11.0% (4.40, 1.87–10.38). Higher HbA1c also predicted elevated CRP in the regression model when HbA1c was analyzed as a continuous variable (1.20, 1.07–1.34). CONCLUSIONS—In this study, the likelihood of elevated CRP concentrations increased with increasing HbA1c levels. These findings suggest an association between glycemic control and systemic inflammation in people with established diabetes.