The Impact of Systolic Blood Pressure, Pulse Pressure, and Their Variability on Diabetes Retinopathy among Patients with Type 2 Diabetes

OBJECTIVES: To evaluate the effects of variations in systolic blood pressure (SBP) and pulse pressure (PP) on diabetic retinopathy (DR) in patients with type 2 diabetes. METHODS: A total of 3275 type 2 diabetes patients without DR at Taiwan Lee's United Clinic from 2002 to 2014 were enrolled in the study. The average age of the patients was 65.5 (±12.2) years, and the follow-up period ranged from 3 to 10 years. Blood pressure variability was defined as the standard deviation (SD) of the average blood pressure values over the entire study period and was calculated for each patient. The mean SD for SBP was 11.16, and a SBP ≥ 130 mmHg (1 mmHg = 0.133 kPa) was defined as high SBP. Based on these data, patients were divided into four groups as follows: group 1 (G1, mean SBP < 130 mmHg, SD of SBP < 11.16 mmHg), group 2 (G2, mean SBP < 130 mmHg, SD ≥ 11.16 mmHg), group 3 (G3, mean SBP ≥ 130 mmHg, SD of SBP < 11.16 mmHg), and group 4 (G4, mean SBP ≥ 130 mmHg, SD ≥ 11.16 mmHg). Based on a mean PP of 80 mmHg with a pulse pressure SD of 6.53 mmHg, the patients were regrouped into four groups designated G1′-G4′. RESULTS: After adjusting for patient age, sex, and disease course, Cox regression showed that the mean and SD of SBP, pulse pressure, and their SDs were risk factors for DR. After stratifying the patients based on the mean and SD of the SBP, we found that the patients in the G4 group had the highest risk of DR (hazard ratio (HR) = 1.980, 95% CI: 1.716~2.285, P < 0.01) and patients in the G1 group had the lowest risk. Patients in the G3 group (HR = 1.409, 95% CI: 1.284~1.546, P < 0.01) had a higher risk of DR compared to those in the G2 group (HR = 1.353, 95% CI: 1.116~1.640, P < 0.01). After the restratification of patients based on the mean and SD of the pulse pressures, it was found that patients in the G2′ group had the highest risk of DR (HR = 2.086, 95% CI: 1.641~2.652, P < 0.01), whilst patients in the G1′ group had the lowest risk. Also, the risk of DR in the G4′ group (HR = 1.507, 95% CI: 1.135~2.000, P < 0.01) was higher than that in the G3′ group (HR = 1.289, 95% CI: 1.181~1.408, P < 0.01). CONCLUSIONS: Variability in SBP and PP are risk factors for DR in patients with type 2 diabetes. The variability of PP was better able to predict the occurrence of DR than mean pulse pressure.