Table 2 Meta-analysis of risk factors for postoperative delirium in older spinal surgical patients

 Age > 65 years

2

IV, fixed

6.13 (5.75, 6.54)

0.0

0.000

 Age > 70 years

3

IV, random

18.23 (3.13, 107.34)

48.4

0.001

 Sex (% female)

8

IV, fixed

1.21 (1.15, 1.28)

0.001

0.000

 Mean age

6

IV, fixed

1.34 (0.34, 2.33)

6.0

0.009

 Number of medication

3

IV, random

0.92 (− 0.05, 1.88)

77.5

0.063

 Surgical history

6

IV, fixed

2.22 (1.47, 3.34)

0.0

0.000

 Diabetes mellitus

7

IV, random

2.80 (1.15, 6.79)

70.6

0.023

 Cerebral vascular diseases

3

IV, fixed

3.18 (1.27, 7.79)

15.7

0.014

 Low hematocrit (%)

3

IV, fixed

− 1.66 (− 2.94, − 0.38)

0.0

0.011

 Low hemoglobin (g/L)

4

IV, fixed

− 0.41 (− 0.75, − 0.07)

0.0

0.017

 Low albumin (g/dL)

2

IV, fixed

− 0.30 (− 0.50, − 0.11)

18.7

0.003

 Low sodium

4

IV, random

− 1.81 (− 3.33, − 0.30)

77.8

0.019

 Low potassium

2

IV, random

0.00 (− 0.28, 0.28)

45.4

0.996

 Blood sugar

2

IV, random

0.13 (− 0.52, 0.78)

33.4

0.698

 Hypertension

7

IV, random

2.01 (1.04, 3.88)

58.3

0.038

 Depression

2

IV, fixed

2.02 (1.00, 4.06)

0.0

0.049

 Operating time

9

IV, random

29.42 (1.12, 57.72)

87.9

0.042

 Total blood loss

8

IV, fixed

116.77 (93.66, 139.88)

14.9

0.000

 Fusion level

2

IV, random

0.35 (− 0.72, 1.42)

52.3

0.524

 Intravenous fluids

4

IV, random

231.24 (− 137.99, 600.47)

68.9

0.220

 Low sodium (mEq/L)

4

IV, random

− 3.05 (− 5.47, − 0.63)

89.7

0.014

 Low hemoglobin (g/L)

6

IV, random

− 0.76 (− 1.24, − 0.29)

82.5

0.002

 Low hematocrit (%)

3

IV, fixed

− 2.53 (− 3.59, − 1.47)

0.0

0.000

 Low albumin (g/dL)

2

IV, fixed

− 0.10 (− 0.27, 0.07)

0.0

0.245

 Fever

2

IV, fixed

4.52 (2.94, 6.95)

0.0

0.000

 Low potassium

4

IV, random

− 3.05 (− 5.47, − 0.63)

89.7

0.014

 Blood sugar

1

IV, fixed

1.00 (1.00, 1.96)

0.0

0.041

 VAS

2

IV, random

0.98 (0.11, 1.85)

55.4

0.027