Yokoyama 1994.

Study characteristics
Methods	Study design: retrospective cohort longitudinal Location: Japan Time period: 1951 to 1984 Outcome: PDR Outcome measurement: incidence
Participants	Number of participants: 373 Diabetes type: T1D Inclusion criteria: all patients who visited the Diabetes Centre, Tokyo Women’s Medical College, in whom IDDM had been diagnosed between 1951 and 1984 and before the age of 30 years Exclusion criteria: incomplete registration; PDR
Notes	Link to data extraction table, risk of bias assessment, and results: osf.io/j5ufs/?view_only=747af7be9845495aa647787470791f85
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	Unclear	See ‘Notes’ above for link to risk of bias assessment