Table 3 Detailed outcomes on insulin use and RRs of DR

All subjects

7

2.30

1.35-3.93

< 0.001

89.3

Study design

Prospective study

6

2.38

1.28-4.41

< 0.001

90.9

Retrospective study

1

2.30

1.11-3.43

—

—

Geographic location

Europe

5

1.85

1.12-3.08

< 0.001

80.4

Asia

1

3.43

1.93-6.08

—

—

North America

1

4.90

2.63-5.79

—

—

Data source

Population based

5

2.94

2.19-3.94

0.234

28.1

Hospital based

2

1.34

0.65-2.76

0.024

80.5

Follow-up duration

≥ 5 years

1

3.51

1.59-7.76

—

—

< 5 years

6

2.17

1.22-3.85

< 0.001

90.3

Major confounders adjusted

DM duration

Yes

3

2.18

0.80-5.93

< 0.001

91.7

No

4

2.53

1.74-3.67

0.115

49.4

HbA1c

Yes

3

2.88

2.00-4.14

0.454

0

No

4

2.30

1.35-4.14

< 0.001

92.7