Nelson 1989.

Study characteristics
Methods	Study design: registry data Location: USA Time period: recruitment: 13 October 1983 to 30 November 1987 Outcome: PDR Outcome measurement: incidence, RR, and incidence rate ratio
Participants	Number of participants: 953 Diabetes type: T2D Inclusion criteria: all diabetic people who lived in the Gila River Indian Community at any time between 13 October 1983 and 30 November 1987; whose heritage was at least 50% Pima, Papago, or a mixture of these closely related tribes; and who had undergone biennial research examinations Exclusion criteria: not reported
Notes	Link to data extraction table, risk of bias assessment, and results: osf.io/dc2bf/?view_only=e50fc6f6134c4f26b635768d365a4ef1
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	Unclear	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