Risk factor analysis for further retinopathy progression from DCCT closeout through EDIC year 10 Weibull model with interval censoring

Covariateχ2PHR (95% CI)*
At DCCT entry
    Type 1 diabetes duration (year)3.20.07620.97 (0.94–0.02)
    Primary vs. secondary cohort0.00.94941.01 (0.77–1.32)
    A1C level at DCCT eligibility (%)38.0<0.00011.19 (1.12–1.25)
At EDIC entry
    Retinopathy level
        Microaneurysms only vs. no retinopathy24.3<0.00010.53 (0.41–0.68)
        Mild nonproliferative vs. no retinopathy13.20.00030.58 (0.43–0.78)
        Moderate or severe vs. no retinopathy3.90.04961.41 (1.33–2.24)
    Mean blood pressure (mmHg)§18.6<0.00011.12 (1.06–1.17)
    Elevated lipid (yes vs. no)16.6<0.00011.72 (1.33–2.24)
Age (adolescent vs. adult) at DCCT enrollment7.10.0079
DCCT treatment group (CT vs. INT)1.70.1928
DCCT treatment group by age (adolescent vs. adult)4.30.0381
Treatment effect (CON vs. INT)
    In adult cohort: CON vs. INT (df = 1)64.3<0.00012.3 (1.9–2.9)
    In adolescent cohort: CON vs. INT (df = 1)1.70.19271.4 (0.9–2.2)
    Overall treatment effect: CON vs. INT (df = 2)7.10.0290
Age effect (adolescent vs. adult)
    In INT group: adolescent vs. adult (df = 1)7.10.00781.7 (1.1–2.5)
    In CT group: adolescent vs. adult (df = 1)0.00.97371.0 (0.7–1.4)
    Overall age effect (adolescent vs. adult) (df = 2)65.3<0.0001
Model log likelihood−1,445.2
  • *HR is the ratio of hazard of retinopathy progression for a 1-unit increase in quantitative variables or change in status for dichotomous variables if without notation.

  • †HR is based on a 5-unit increase in type 1 diabetes duration (year)/mean blood pressure (mmHg).

  • ‡The EDIC entry data are the same as DCCT closeout data.

  • §Mean blood pressure = 2/3 diastolic blood pressure + 1/3 systolic blood pressure.

  • ‖Elevated lipid is defined as two consecutive reports of hypercholesterolemia (LDL cholesterol >160 mg/dl) and/or hypertriglyceridemia (triglycerides >500 mg/dl) within 1 month during DCCT. Data in bold face are statistically significant.