Comparison 2. Subgroup analysis: severe TBI subgroup (GCS ≤ 8).

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Mortality at the end of the follow‐up period	5	2369	Risk Ratio (M‐H, Random, 95% CI)	0.95 [0.70, 1.29]
1.1 severe TBI subgroup (GCS ≤ 8）	5	2090	Risk Ratio (M‐H, Random, 95% CI)	0.87 [0.60, 1.27]
1.2 moderate TBI subgroup (GCS 9 to 12)	2	279	Risk Ratio (M‐H, Random, 95% CI)	1.30 [0.70, 2.41]
2 Death or severe disability (GOS1 to 3) at the end of the follow‐up period	4	2260	Risk Ratio (M‐H, Random, 95% CI)	0.92 [0.78, 1.08]
2.1 severe TBI subgroup (GCS ≤ 8）	4	2002	Risk Ratio (M‐H, Random, 95% CI)	0.99 [0.87, 1.11]
2.2 moderate TBI subgroup	2	258	Risk Ratio (M‐H, Random, 95% CI)	0.68 [0.34, 1.37]