Table 2.
Results of multivariate Cox regression analysis for the independent predictors of the composite and separate endpoints (development and/or progression of diabetic retinopathy) measured at different time-intervals during follow-up.
| Blood pressure parameters | Composite endpoint: retinopathy development/progression (n = 544 patients, 156 endpoints) | Separate endpoint: retinopathy progression (n = 144 patients, 79 endpoints) | Separate endpoint: retinopathy development (n = 400 patients, 77 endpoints) | ||||||
|---|---|---|---|---|---|---|---|---|---|
| HR | 95% CI | p-value | HR | 95% CI | p-value | HR | 95% CI | p-value | |
| Model 1: Baseline variables | |||||||||
| Diabetes duration (1 year) | 1.03 | 1.01, 1.05 | 0.012 | 1.01 | 0.98, 1.04 | 0.59 | 1.04 | 1.01, 1.07 | 0.006 |
| HbA1c (1-SD) | 1.33 | 1.13, 1.56 | 0.001 | 1.59 | 1.20, 2.10 | 0.001 | 1.25 | 1.01, 1.56 | 0.045 |
| Ambulatory 24-h DBP (1-SD) | 1.22 | 1.03, 1.46 | 0.024 | 0.98 | 0.74, 1.30 | 0.89 | 1.37 | 1.10, 1.71 | 0.005 |
| LDL-cholesterol (1-SD) | 1.17 | 1.00, 1.37 | 0.049 | 1.31 | 1.04, 1.67 | 0.025 | 1.11 | 0.90, 1.38 | 0.34 |
| Model 2: First-year variables | |||||||||
| Diabetes duration (1 year) | 1.03 | 1.01, 1.05 | 0.010 | 1.02 | 0.99, 1.05 | 0.29 | 1.04 | 1.01, 1.07 | 0.005 |
| HbA1c (1-SD) | 1.26 | 1.07, 1.48 | 0.006 | 1.26 | 1.01, 1.60 | 0.048 | 1.25 | 1.01, 1.58 | 0.046 |
| Clinic DBP (1-SD) | 1.14 | 0.95, 1.37 | 0.15 | 0.96 | 0.70, 1.32 | 0.81 | 1.25 | 1.00, 1.56 | 0.050 |
| Aortic stiffness (cf-PWV 1 m/s) | 1.03 | 0.94, 1.13 | 0.49 | 0.95 | 0.84, 1.09 | 0.48 | 1.11 | 0.99, 1.24 | 0.073 |
| Model 3: Second-year variables | |||||||||
| Diabetes duration (1 year) | 1.03 | 1.01, 1.05 | 0.002 | 1.03 | 0.99, 1.06 | 0.14 | 1.04 | 1.01, 1.07 | 0.006 |
| HbA1c (1-SD) | 1.36 | 1.18, 1.56 | <0.001 | 1.30 | 1.05, 1.60 | 0.016 | 1.40 | 1.16, 1.69 | 0.001 |
| Clinic DBP (1-SD) | 1.27 | 1.06, 1.51 | 0.010 | 1.23 | 0.93, 1.62 | 0.15 | 1.28 | 1.01, 1.63 | 0.039 |
| Model 4: Cumulative variables during the whole follow-up (until censoring or endpoint occurrence) | |||||||||
| Diabetes duration (1 year) | 1.04 | 1.02, 1.06 | <0.001 | 1.03 | 0.99, 1.06 | 0.12 | 1.05 | 1.02, 1.08 | 0.001 |
| Clinic DBP (1-SD) | 1.36 | 1.14, 1.61 | 0.001 | 1.13 | 0.86, 1.50 | 0.38 | 1.53 | 1.24, 1.90 | <0.001 |
| HbA1c (1-SD) | 1.30 | 1.10, 1.54 | 0.003 | 1.28 | 1.01, 1.63 | 0.038 | 1.29 | 1.00, 1.65 | 0.050 |
| LDL-cholesterol (1-SD) | 1.17 | 1.00, 1.39 | 0.057 | 1.29 | 0.98, 1.69 | 0.073 | 1.07 | 0.88, 1.34 | 0.45 |
Candidate variables to enter the models were the following: age, sex, BMI, smoking status, physical activity, presence of any macro- and microvascular complications, diabetes duration and classes and numbers of anti-diabetic and anti-hypertensive medications (in all models); ambulatory 24-hour systolic and diastolic blood pressures (in the baseline model); aortic stiffness (in the first-year model); and baseline, mean first-year, second-year and cumulative HbA1c, LDL- and HDL-cholesterol, and clinic systolic and diastolic blood pressures (in their respective models). Regardless of their significance, all models were further adjusted for age, sex and presence of diabetic retinopathy, nephropathy and peripheral neuropathy at baseline.
Abbreviations: HR, hazard ratio; CI, confidence interval; HbA1c, glycated hemoglobin; SD, standard deviation; DBP, diastolic blood pressure; LDL, low-density lipoprotein.