Table 3.

Subgroup analysis for included studies

Subgroups	Studies (n)	Participant (n)	Mean difference			Effect size
			Mean difference (95% CI)	Q test	I²(%)	Effect size (95% CI)	Q test	I²(%)
Eight-hour pain score age group
< 70	3	268	1.238 (0.175, 2.301) *	25.271	92.086 ***	1.009 (0.461, 1.558) ***	8.729	77.089 **
70 and more	3	243	0.546 (-0.210, 1.302)	18.279	89.059 ***	1.266 (-0.209, 2.741)	49.998	96.000 ***
Twenty-four-hour pain score age group
< 70	4	316	0.809 (0.445, 1.173) ***	5.252	42.883	0.802 (0.380, 1.224) ***	9.427	68.177 *
70 and more	4	303	0.402 (-0.523, 1.326)	35.166	91.469 ***	1.131 (-0.086, 2.347)	66.888	95.515 ***
Forty-eight-hour pain score age group
< 70	3	231	0.635 (0.099, 1.172) *	5.446	63.278	0.538 (0.157, 0.919) **	3.836	47.856
70 and more	4	303	1.083 (0.473, 1.692) ***	24.334	87.672 ***	1.549 (0.465, 2.632) **	50.873	94.103 ***
Twenty-four-hour pain score BMI group
< 30	6	467	0.690 (0.203, 1.177) ***	56.129	91.092 ***	1.156 (0.325, 1.986) ***	78.148	93.602 ***
30 and more	2	152	0.492 (-1.265, 2.248) **	7.945	87.414**	0.266 (-0.647, 1.179) **	8.554	88.310 **
Forty-eight-hour pain score BMI group
< 30	5	382	0.760 (0.169, 1.351) ***	39.337	89.831 ***	1.158 (0.284, 2.033) *	54.959	92.722 ***
30 and more	2	152	1.251 (0.402, 2.100) ***	2.652	62.297	0.821 (0.519, 1.123) **	0.214	0.000

CI confidence interval

P < 0.05, *; P < 0.01, **; P < 0.001, ***