1. Gender ‐ Studies undertaking multivariable regression analyses to determine the effect of gender on progression to PDR.
| Study | Study type | Time years | N at baseline | Adjustment factors | Effect estimate | P value | Comments | ||
| Type | Value | 95% CI | |||||||
| Type 1 diabetes | |||||||||
| No multivariable regression analyses | |||||||||
| Type 2 diabetes | |||||||||
| Nelson 1989 | Prospective cohort | 4 | 953 | DM duration, age | RR | 1.5 | 0.7 to 3.4 | Male vs female | |
| Gange 2021 | Retrospective cohort (electronic database) | 5 | 718 | Maximum HbA1c, gender, smoking, comorbidities, obesity, insulin use, education, hypertension, dyslipidaemia, diabetic ketoacidosis | Gender reported narratively in text as being non‐significant. | ||||
| Lee 2021 | Retrospective cohort | 6 | 2623 | HbA1c, DR severity at baseline, age, BMI | Male vs female | ||||
| Type 1 and type 2 diabetes | |||||||||
| Lee 2017 | Retrospective cohort (electronic database) | 5 | 32,553 | DR severity at baseline, age, ethnicity, features of DR | HR | 0.92a | 0.71 to 1.19 | 0.53 | |
| Harris 2013 | Retrospective cohort (electronic database) | 5 | 4617 | HbA1c, age, ethnicity, comorbidities, medications | HR | 1.08 | 0.94 to 1.22 | ||
| Jeng 2016 | Retrospective cohort (electronic database) | 5 | 53,453 | Age, comorbidities, medications | HR | 0.99 | 0.85 to 1.15 | Female vs male | |
BMI: body mass index; CI: confidence interval; 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; vs: versus
a Reference gender not reported: authors contacted but unable to confirm