Table 8 Subgroup analysis of risk factors

Diabetes mellitus

China

13

2.3676 (1.5612–3.5905)

< 0.001

57.3%

0.0053

Japan

5

0.9459 (0.3934–2.2742)

0.9011

71.8%

0.0068

Open surgery

6

1.8982 (0.7942–4.5368)

0.1494

77.9%

< 0.001

Laparoscopic surgery

10

2.1436 (1.1005–4.1752)

0.0250

73.9%

< 0.001

≥ 60

16

1.9006 (1.1831–3.0534)

0.0079

68.1%

< 0.001

< 60

15

1.9275 (1.1616–3.1984)

0.0111

70.1%

< 0.001

Nutritious status

China

10

2.1919 (1.1518–4.1711)

0.0168

74.4%

< 0.001

Japan

4

1.1607 (0.2380–5.6612)

0.8538

85.3%

< 0.001

Open surgery

7

1.5359 (0.5400–4.3682)

0.4210

80.9%

< 0.001

Laparoscopic surgery

9

1.6927 (0.7531–3.8044)

0.2027

77.8%

< 0.001

≥ 60

12

1.4677 (0.8036–2.6807)

0.2118

72.7%

< 0.001

< 60

10

1.4149 (0.6966–2.8739)

0.3371

76.6%

< 0.001

History of pulmonary disease

China

9

1.3351 (0.3931–4.5339)

0.6432

89.2%

< 0.001

Japan

4

2.0478 (1.2583–3.3326)

0.0039

0.0%

0.6369

Open surgery

5

1.6270 (1.1546–2.2927)

0.0054

0.0%

0.5305

Laparoscopic surgery

8

2.6105 (1.5242–4.4710)

< 0.001

61.5%

0.0111

≥ 60

12

1.5534 (0.6214–3.8836)

0.3461

85.6%

< 0.001

< 60

10

1.4216 (0.4718–4.2835)

0.5320

87.8%

< 0.001

Perioperative blood transfusion

China

7

3.2074 (2.3789–4.3245)

< 0.001

0.0%

0.5205

Japan

3

3.6842 (1.9768–6.8661)

< 0.001

0.0%

0.3844

Open surgery

6

3.1215 (2.2283–4.3727)

< 0.001

0.0%

0.5196

Laparoscopic surgery

7

2.9034 (2.1228–3.9710)

< 0.001

0.0%

0.5565

≥ 60

8

3.6480 (2.7172–4.8976)

< 0.001

0.0%

0.6117

< 60

6

4.1390 (2.9861–5.7371)

< 0.001

0.0%

0.8062

Prolonged postoperative nasogastric tube retention

China

9

2.4757 (1.6358–3.7469)

< 0.001

58.7%

0.0130

Japan

0

Open surgery

4

1.8991 (1.2259–2.9420)

0.0041

25.1%

0.2606

Laparoscopic surgery

5

1.7034 (1.2672–2.2896)

0.0004

5.9%

0.3732

≥ 60

8

2.3913 (1.5498–3.6895)

< 0.001

62.0%

0.0102

< 60

8

2.3913 (1.5498–3.6895)

< 0.001

62.0%

0.0102