Nielsen 1984.

Study characteristics
Methods	Study design: prospective cohort longitudinal Location: Denmark Time period: recruitment: 1980 to 1982 Outcome: PDR Outcome measurement: incidence
Participants	Number of participants: 227 Diabetes type: T1D Inclusion criteria: insulin‐treated diabetes, identified from prescription registrations for insulin; 1 year follow‐up Exclusion criteria: not reported
Notes	Link to data extraction table, risk of bias assessment, and results: osf.io/dw5hu/?view_only=95205550ab53454c903a2e3b4178aa49
Item	Authors' judgement	Support for judgement
Study participation	Unclear	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	Unclear	See ‘Notes’ above for link to risk of bias assessment
Adjustment for other prognostic factors	No	See ‘Notes’ above for link to risk of bias assessment
Statistical analysis and reporting	Unclear	See ‘Notes’ above for link to risk of bias assessment