Ballard 1986.

Study characteristics
Methods	Study design: retrospective cohort longtitudinal Location: USA Time period: DM diagnosed between 1945 and 1969 and followed through complete medical records to 31 Dec 1981 Outcome: PDR Outcome measurement: incidence density, cumulative incidence
Participants	Number of participants: 1031 Diabetes type: NIDDM Inclusion criteria: NIDDM Exclusion criteria: IDDM; secondary diabetes
Notes	Link to data extraction table, risk of bias assessment, and results: osf.io/8f5zr/?view_only=1f191b99e38a4e55be1916411610f508
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