C-reactive protein, body mass index, and diabetic retinopathy

C-reactive protein (CRP) is an inflammatory biomarker that may be associated with diabetic retinopathy (DR), but body mass index (BMI) is an important confounder of this relationship. The purpose of this study was to determine the relationship between CRP, BMI, and existing DR.

This was a population-based, cross-sectional study on 718 persons with diabetes in the Singapore Malay Eye Study (SiMES). Diabetes was defined as random glucose>or=11.1 mmol/L, on diabetic medication or a history of physician-diagnosed diabetes. CRP was measured in frozen plasma. DR was graded from retinal photographs.

Higher CRP and BMI were associated with lower prevalence of DR. After adjustment for age, sex, HbA1c level, hypertension, smoking, total cholesterol level, cholesterol-lowering medication, and insulin use, persons with the highest quartiles of CRP were less likely to have any DR (odds ratio [OR] 0.5; 95% CI, 0.3-0.9, comparing the fourth with the first quartile of CRP), vision-threatening DR (OR 0.3; 95% CI, 0.1-0.7), or CSME (OR 0.2; 95% CI, 0.1-0.6). Similarly, persons with the highest quartiles of BMI were less likely to have any DR (OR 0.5; 95% CI, 0.3-0.7), moderate DR (OR 0.4; 95% CI, 0.2-0.7), vision-threatening DR (OR 0.4; 95% CI, 0.1-0.8) or CSME (OR 0.2; 95% CI, 0.0-1.0). No significant interactions between CRP and BMI on DR were seen.

Persons with diabetes who had higher levels of CRP and BMI were less likely to have DR. Further research is needed to understand the interrelationship role of inflammation, body weight, and microvascular complications.