Nonlinear Relationship between Systolic Blood Pressure and Diabetic Retinopathy in Type 2 Diabetic Patients in Southern China: A Single-Center Observational Study

Abstract

Systolic blood pressure (SBP) has been shown to have a positive correlation with diabetic retinopathy (DR). However, the SBP thresholds have not been standardized for DR prevention. We analyzed data from a cross-sectional study (December 2017-November 2018, n = 426, mean age 59.15±13.68) from the Department of Endocrinology, Guangdong Provincial People's Hospital in patients with type 2 diabetes mellitus. DR severity was assessed by retinal photographs. The International Clinical Diabetic Retinopathy and Diabetic Macular Edema Disease Severity Scale was used to classify DR severity and divide it into two groups: with DR and without DR. SBP was analyzed as a continuous variable. Multivariate logistic regression models, smoothed curve fitting, threshold analysis, and interaction tests were used to assess the relationship between BP and DR. Prevalence of DR in the study population was 39.20%. After adjusting for age, sex, DM duration, HbA1c, BUN, HDL, LDL, TRIG, CHOL, TP, DBP, PP, eGFR, and CKD stage, the association between SBP and DR appears as a threshold effect, with a inflection point of 132mmHg. The risk of DR did not change significantly when SBP ≤132mmHg (OR: 0.86; 95% CI: 0.63 to 1.17, p=0.3400). When SBP ≥132mmHg, each 10 mmHg increase in SBP raise the risk of developing DR by 28% (OR:1.28; 95% CI:1.07 to 1.54, P=0.0081). In addition, a stronger association of SBP with DR in patients with TP≤60g/L (OR=1.58, 95% CI: 1.19- 2.08, P=0.001) compared to those with TP>60g/L (OR=1.15, 95% CI: 1.03, 1.27, P=0.012) was discovered, with a P value for interaction=0.023.