Simonsen 1980.

Study characteristics
Methods	Study design: prospective cohort longitudinal Location: Denmark Time period: initial examination: 1964 to 1966; final re‐examination: 1972 to 1979 Outcome: PDR Outcome measurement: incidence
Participants	Number of participants: 141 Diabetes type: T1D Inclusion criteria: T1D; age 17 to 50 years; controlled at regular intervals at the Steno Memorial Hospital; DM diagnosed prior to 40 years Exclusion criteria: refractive errors exceeding 3D; eye diseases other than DR; consumption of drugs known to influence electroretinogram; pregnant
Notes	Link to data extraction table, risk of bias assessment, and results: osf.io/ryvfc/?view_only=25209546db9e497a9008cd7e44de5ac6
Item	Authors' judgement	Support for judgement
Study participation	Unclear	See ‘Notes’ above for link to risk of bias assessment
Study attrition	No	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	No	See ‘Notes’ above for link to risk of bias assessment