Guomiao Zhang

Background The prevalence and incidence rates of type 2 diabetes mellitus (T2DM) have risen steadily globally since 1990. Previous studies reported that 529 million people of all ages worldwide have diabetes, the prevalence of diabetes has increased from 3·2% (3·0–3·5) to 6·1% in 2021, and the prevalence of diabetes has increased by 59.7% (95% CI: 54·7–66·0) from 6.1% (5·8–6·5) to 9·8% (9·4–10·2), resulting in 1.31 billion (1·22–1·39) people living with diabetes in 2050 (1).

This investigation adopted a two-center case–control study in China. Detailed information about the study design and participant recruitment can be found in our previous publications [17,18,19]. In brief, the present study comprised 195 patients diagnosed with type 2 diabetes mellitus (T2DM), of which 83 exhibited DR and 112 did not.