Abstract
Purpose: :
C-reactive protein (CRP) is an inflammatory biomarker that may be associated with diabetic retinopathy (DR) risk, but body mass index (BMI) is an important confounder of this relationship. The aim of this study is to determine the relationship between BMI, CRP, and the presence and severity of DR, in adult persons with diabetes mellitus.
Methods: :
This population-based, cross-sectional study included persons with diabetes from the Singapore Malay Eye Study (SiMES). The SiMES examined 3,280 (78.7% response) persons aged 40-80 years of Malay ethnicity in Singapore. Diabetes mellitus was defined as random glucose≥11.1mmol/l, on diabetic medication or having a history of physician diagnosed diabetes. Serum CRP was measured in frozen plasma using an immunoturbidimetric assay. DR was graded from retinal photographs. Any DR was defined by characteristic lesions defined by the Early Treatment Diabetic Retinopathy Study (ETDRS), moderate DR was defined as ETDRS retinopathy severity scores 43 or higher, and vision-threatening retinopathy was defined as severe non-proliferative retinopathy (NPDR), proliferative DR, or clinically significant macular edema (CSME).
Results: :
Of 3,280 participants, 718 persons with diabetes were included in this report. After adjusting for age, gender, HbA1c level, hypertension, smoking, total cholesterol level, and cholesterol lowering medication use, subjects in the highest quartiles of BMI were less likely to have any DR (p for trend = 0.001), moderate DR (p for trend = 0.001), vision threatening DR (p for trend = 0.005) or any CSME (p for trend =0.04). After further adjusting for insulin use, subjects with the highest quartiles of CRP were less likely to have any DR (per log unit increase in CRP levels, OR 0.8), vision threatening DR (OR 0.7) and CSME (OR 0.5). In subgroup analyses, these inverse associations were evident only in persons (mainly women) who were both overweight and had the highest quartiles of CRP. No significant interactions between BMI and CRP were found.
Conclusions: :
We found in this Malay study sample that persons with diabetes who had both high BMI and high levels of CRP were less likely to have DR. Further research is needed to understand the role of body weight and inflammation on the risk of DR.
Keywords: diabetic retinopathy • clinical (human) or epidemiologic studies: risk factor assessment • inflammation