Association Between Elevated C-Reactive Protein Levels and Prediabetes in Adults, Particularly Impaired Glucose Tolerance.

Objectives: Prediabetes is a precursor of diabetes and increases the risk for cardiovascular disease. A high C-reactive protein (CRP) level is a risk factor for diabetes, and individuals with prediabetes have higher CRP levels than those with normal glucose tolerance. In addition, systemic inflammation may play a role in the early-phase deterioration of glucose metabolism. We examined the association between serum CRP levels and prediabetes.

Methods: Overall, 4,101 subjects without diabetes underwent oral glucose tolerance tests. Levels of serum CRP were divided into quartiles; the lowest quartile was used as the reference when calculating odds ratios (ORs) and confidence intervals. Isolated fasting glucose, isolated glucose tolerance and elevated glycated hemoglobin levels (i.e. between 42 and 47 mmol/mol [6.0% to 6.4%]) were indicative of prediabetes.

Results: In the multiple logistic regression analysis, the ORs (95% confidence intervals) for impaired glucose tolerance, impaired fasting glucose and elevated glycated hemoglobin levels corresponding to the highest quartile of CRP levels were 1.67 (1.31 to 2.14); 1.62 (1.15 to 2.28); and 1.47 (1.14 to 1.90), respectively. In the stratified analysis, the ORs for impaired glucose tolerance were consistently higher in the uppermost quartile than in the reference quartile in both the presence and absence of hypertension or dyslipidemia. In contrast, the ORs for impaired fasting glucose in the uppermost quartile were higher only in the presence of hypertension and dyslipidemia, and the OR for elevated glycated hemoglobin levels in the uppermost quartile was higher only in the presence of hypertension.

Conclusions: Elevated serum CRP levels are associated with prediabetes, particularly impaired glucose tolerance.