Klein 1984.

Study characteristics
Methods	Study design: prospective cohort longitudinal Location: USA Time period: baseline: 1970 to 1971; follow‐up: 1976 to 1977 Outcome: PDR Outcome measurement: incidence
Participants	Number of participants: 191 Diabetes type: T1D Inclusion criteria: on insulin since DM diagnosis, if asymptomatic and diagnosed through routine examination must have become symptomatic and taken insulin within one year of diagnosis; ≥ 5 years duration; under care of cooperating GPs for at least 2/3 of the duration of DM Exclusion criteria: overweight; ≥ 50 years
Notes	Link to data extraction table, risk of bias assessment, and results: osf.io/cz5vn/?view_only=940908b18a9c4a14873f1cf4ab26c03a
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	Yes	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