WESDR.

Study characteristics
Methods	Study design: prospective cohort longitudinal Location: USA Time period: baseline: 1980 to 1982; follow‐up 1984 to 1986 Outcome: PDR Outcome measurement: incidence, OR, and RR
Participants	Number of participants: 2366 Diabetes type: T1DM and T2DM Inclusion criteria: younger‐onset group: IDD before 30 years. Older‐onset group: diagnosed with DM at 30 years or older and diagnosis confirmed by a casual or a postprandial serum glucose level of at least 11.1 mmol/L or a fasting serum glucose level of 7.8 mmol/L or greater on at least two occasions. Exclusion criteria: not reported
Notes	Link to data extraction table, risk of bias assessment, and results: osf.io/uh5sx/?view_only=8ed60b81079b4f8dab6a352967b07b4a
Item	Authors' judgement	Support for judgement
Study participation	Yes	See ‘Notes’ above for link to risk of bias assessment
Study attrition	Unclear	See ‘Notes’ above for link to risk of bias assessment
Prognostic factor measurement	Unclear	See ‘Notes’ above for link to risk of bias assessment
Outcome measurement	Yes	See ‘Notes’ above for link to risk of bias assessment
Adjustment for other prognostic factors	Unclear	See ‘Notes’ above for link to risk of bias assessment
Statistical analysis and reporting	Yes	See ‘Notes’ above for link to risk of bias assessment