4. Duration of diabetes ‐ Studies undertaking multivariable regression analyses to determine the effect of duration of diabetes on progression to PDR.
| Study | Study type | Time years | N at baseline | Adjustment factors | Effect estimate | P value | Comments | ||
| Type | Value | 95% CI | Per increase in one year | ||||||
| Type 1 diabetes | |||||||||
| Lloyd 1995 | Prospective cohort | 2 | 496 | HbA1c, DR severity at baseline, follow‐up period | RR | 1.03 | 0.94 to 1.12 | ||
| Janghorbani 2000 | Retrospective cohort | 5 | 1349 | HbA1c, SBP | RR | 1.00a 0.78b 1.95c 3.05d |
0.43 to 1.41 1.23 to 3.09 2.09 to 4.45 |
Nonsignificant < 0.01 < 0.001 |
|
| Porta 2001 | Prospective cohort | 7 | 2013 | HbA1c, age, DM diagnosis < 12 years, DBP, albumin excretion rate, waist‐to‐height ratio | Regression estimate | 1.71 1.12e |
1.42 to 2.06 0.89 to 1.42 |
0.0001 0.3 |
Increasing duration of diabetes |
| Kalter‐Leibovici 1991 | Prospective cohort | 10 | 330 | HbA1c, age, sex, race, socioeconomic status | OR | 1.20 | 1.1 to 1.3 | Increasing duration of diabetes | |
| Grauslund 2009 | Prospective cohort | 25 | 573 | HbA1c, DR severity at baseline, age, sex, SBP, DBP, proteinuria, BMI, smoking status, maculopathy | OR | 0.69 | 0.35 to 1.36 | Per 10 years | |
| Type 2 diabetes | |||||||||
| Gui 2013 | Retrospective cohort | 2 | 205 | Age, hypertension, smoking status, C‐peptide | OR | 1.18 | 1.13 to 1.25 | < 0.05 | Mean |
| Janghorbani 2000 | Retrospective cohort | 5 | 2133 | Unclear | RR | 1.77f 1.37g |
1.15 to 2.72 0.83 to 2.26 |
< 0.05 > 0.05 |
Insulin Non‐insulin |
| Kim 1998 | Prospective cohort | 5 | 228 | HbA1c, age, albumin excretion rate, change in BMI | RR | 1.15 | 0.99 to 1.32 | ||
| Kim 2014 | Retrospective cohort | 5 | 452 | HbA1c | HR | 1.21 | 1.10 to 1.79 | 0.17 | Per unit increase |
| Lee 1992 | Prospective cohort | 12 | 354 | Fasting plasma glucose, age, SBP, cholesterol, DM treatment |
Regression estimate | 0.09 | Standard error: 0.03 | < 0.001 | Per unit increase |
| Type 1 and type 2 diabetes | |||||||||
| Janghorbani 2000 | Retrospective cohort | 5 | 3482 | HbA1c, SBP, proteinuria, type of DM | RR | 1.42c 1.95d |
1.10‐1.83 1.58‐2.39 |
< 0.01 < 0.001 |
8 to 11 years ≥ 12 years |
| Keen 2001 | Prospective cohort | 8 | 4483 | Age, sex, SBP, DBP, cholesterol, BMI, smoking status, insulin, type of DM, comorbidities | OR | 1.16 | < 0.01 | Per 5 years | |
BMI: body mass index; CI: confidence interval; DBP: diastolic blood pressure; DM: diabetes mellitus; DR: diabetic retinopathy; HbA1c: glycated haemoglobin/haemoglobin A1c; HR: hazard ratio; NPDR: non‐proliferative diabetic retinopathy; OR: odds ratio; PDR: proliferative diabetic retinopathy; RR: risk ratio; SBP: systolic blood pressure; vs: versus
a< 4 years b4 to 7 years vs. < 4 years c8 to 11 years vs. < 4 years d≥ 12 years vs. < 4 years eModel also included DR severity at baseline f≥ 12 years vs. < 4 years, taking insulin g≥ 12 years vs. < 4 years, not taking insulin