Table 2 Subgroup analysis and meta-regression

All

18

−0.352(− 0.538, − 0.166)

0.000^*

85.7%

0.000^*

Diabetes mellitus type

0.008^*

Type1

4

−0.685(−1.390,0.019)

0.057

89.3%

0.000^*

Type2

10

−0.341(− 0.517,-0.165)

0.000^*

73.2%

0.000^*

Type 1 and 2

4

−0.101(− 0.368,0.185)

0.491

79.9%

0.002^*

area

0.823

Europe

7

−0.501(−0.910,-0.092)

0.016^*

92.6%

0.000^*

Asia

8

−0.214(− 0.366,-0.061)

0.006^*

63.0%

0.008^*

American

3

−0.382(− 0.711,-0.053)

0.023^*

0.0%

0.724

Study design

0.717

Cross-sectional study

16

−0.391(−0.579,-0.203)

0.000^*

84.9%

0.000^*

Case-control study

2

−0.027(− 0.946,0.892)

0.95

91.5%

0.001^*

Sample size

0.285

< 200

10

−0.202(−0.379,-0.025)

0.026^*

51.6%

0.029^*

> 200

8

−0.494(− 0.793,-0.195)

0.001^*

92.2%

0.000^*

Publication year

0.842

< 2010

8

−0.191(−0.401, 0.019)

0.075^*

54.4%

0.032^*

> 2010

10

−0.450(− 0.710,-0.191)

0.001^*

90.6%

0.000^*

Measurement tool

0.438

Contact

12

−0.423(−0.642,-0.203)

0.000^*

88.7%

0.000^*

noncontact

6

−0.158(− 0.465,0.149)

0.312

61.5%

0.024^*