Association between serum C-reactive protein levels and microalbuminuria: a population-based cross-sectional study in northern Iwate, Japan.

OBJECTIVE

The presence of microalbuminuria is a renal marker of vascular endothelial damage, and is an independent and strong predictor of increased risk for cardiovascular mortality and morbidity. Elevated circulating C-reactive protein (CRP) levels have recently been reported to be a novel cardiovascular risk factor, and it has been suggested that this acute-phase protein impairs vascular endothelial function. The aim of the present study was to determine whether serum CRP level is a dependent or an independent risk factor of microalbuminuria in the general population.

METHODS

Subjects of this cross-sectional study were apparently healthy individuals drawn from the general Japanese population (mean age, 62; men, 2,236; women, 4,217). Serum CRP levels were determined using a highly sensitive kit and urine albumin-creatinine ratio (UACR) was calculated using a single urine sample. Multivariate logistic regression analysis was used to determine which risk factors (ie, age, hypertension, diabetes, obesity, hypercholesterolemia, smoking, and CRP) might predict the presence of microalbuminuria.

RESULTS

In addition to classical cardiovascular risk factors such as age, hypertension, diabetes and obesity, serum CRP levels are also significantly correlated with microalbuminuria in men (odds ratio = 1.42, 95% CI = 1.13-1.79; p < 0.01) and women (odds ratio = 1.25, 95% CI = 1.05-1.49; p < 0.01). When subjects with diabetes were excluded from the analysis, serum CRP levels continued to be a significant predictor for microalbuminuria (odds ratio = 1.35, 95% CI = 1.06-1.73; p < 0.05 for men: odds ratio = 1.23, 95% CI = 1.03-1.47; p < 0.05 for women).

CONCLUSIONS

The present study has shown that low-grade inflammation as represented by high sensitivity CRP levels may be significantly related to the presence of microalbuminuria. This suggests that microalbuminuria may be a useful marker representing systemic low-grade inflammation as well as being an established cardiovascular risk factor in apparently healthy individuals.