Baseline characteristics of included TBI patients
A total of 520 TBI patients was included in this study. There were 415 survivors and 105 non-survivors with mortality rate of 20.2% (Table 1). The median age of overall patients was 80 years. There was no significant difference about age between survivors and non-survivors (79 vs 81, p = 0.217). The male ratio also did not differ between these two groups (54% vs 52.4%, p = 0.770). The percentage of underlying disease including hypertension, coronary heart disease and diabetes mellitus did not differ between survivors and non-survivors. However, non-survivors were more likely to be complicated with previous acute myocardial infarction than survivors (11.4% vs 4.8%, p = 0.019). Results of vital signs on admission showed no significant difference between survivors and non-survivors. And non-survivors had higher incidence of pupillary no-reaction whether one or both sides (9.5% vs 3.9%, p = 0.028; 6.7% vs 1.7%, p = 0.011). Furthermore, the GCS of non-survivors was lower than survivors with statistical significance (6 vs 14, p < 0.001). The occurrence rate of several injury patterns including concussion, contusion, laceration, epidural hematoma, subdural hematoma and intracerebral hematoma did not differ between survivors and non-survivors. Whereas non-survivors had significantly higher occurrence rate of subarachnoid hemorrhage than survivors (34.3% vs 24.6%, p = 0.048). The incidence of surgical operation and blood transfusion was higher in non-survivors than survivors without statistical significance (28.6% vs 24.8%, p = 0.435; 40.0% vs 38.3%, p = 0.752). During hospitalization, non-survivors were more likely to suffer arrhythmia than survivors (48% vs 22.3%, p < 0.001). A remarkable finding was that non-survivors had significantly higher level of troponin T than survivors (0.02 vs 0, p < 0.001). Compared with survivors, non-survivors had longer length of ICU stay (4 vs 2, p = 0.001). Instead, the length of hospital stay was shorter in non-survivors than survivors (6 vs 8, p < 0.001).
Table 1
Baseline characteristics of overall patients and subgroups divided based on survival outcome
Variables | Total patients (N = 520) | Survivors (n = 415, 79.8%) | Non-survivors (n = 105, 20.2%) | p |
Age (years) | 80 (67–86) | 79 (67–85) | 81 (67–88) | 0.217 |
Male gender | 279 (53.7%) | 224 (54%) | 55 (52.4%) | 0.770 |
History of underlying disease | | | | |
Hypertension | 328 (63.1%) | 260 (62.7%) | 68 (64.8%) | 0.688 |
Coronary heart Disease | 130 (25%) | 96 (23.1%) | 34 (32.4%) | 0.056 |
Acute myocardial infarction | 32 (6.2%) | 20 (4.8%) | 12 (11.4%) | 0.019 |
Diabetes mellitus | 131 (25.2%) | 100 (24.1%) | 31 (29.5%) | 0.259 |
Vital signs on admission | | | | |
Systolic blood pressure (mmHg) | 139 (127–148) | 139 (128–147) | 139 (124–153) | 0.713 |
Diastolic blood pressure (mmHg) | 62 (58–72) | 62 (59–71) | 62 (52–73) | 0.411 |
Heart rate (s − 1) | 81 (70–93) | 81 (71–92) | 81 (70–94) | 0.840 |
Respiratory rate (s − 1) | 18 (15–21) | 18 (15–21) | 18 (15–21) | 0.659 |
Body temperature (℃) | 36.7 (36.2–37.3) | 36.7 (36.2–37.3) | 36.7 (35.9–37.3) | 0.097 |
SpO2 (%) | 98 (97–100) | 98 (96.9–100) | 99 (97.3–100) | 0.003 |
Pupillary reactivity | | | | |
No-reaction (one side) | 26 (5%) | 16 (3.9%) | 10 (9.5%) | 0.028 |
No-reaction (both sides) | 14 (2.7%) | 7 (1.7%) | 7 (6.7%) | 0.011 |
GCS on admission | 13 (7–15) | 14 (9–15) | 6 (4–10) | < 0.001 |
Injury types | | | | |
Concussion | 11 (2.1%) | 11 (2.7%) | 0 (0) | 0.132 |
Contusion | 15 (2.9%) | 13 (3.1%) | 2 (1.9%) | 0.746 |
Laceration | 75 (14.4%) | 64 (15.4%) | 11 (10.5%) | 0.183 |
Epidural hematoma | 14 (2.7%) | 11 (2.7%) | 3 (2.9%) | 1.000 |
Subdural hematoma | 273 (52.5%) | 223 (53.7%) | 50 (47.6%) | 0.263 |
Subarachnoid hemorrhage | 138 (26.5%) | 102 (24.6%) | 36 (34.3%) | 0.048 |
Intracerebral hematoma | 68 (13.1%) | 48 (11.6%) | 20 (19%) | 0.051 |
Operation | 133 (25.6%) | 103 (24.8%) | 30 (28.6%) | 0.435 |
Blood transfusion | 201 (38.7%) | 159 (38.3%) | 42 (40.0%) | 0.752 |
Arrhythmia during hospitalization | 221 (42.5%) | 169 (40.7%) | 52 (49.5%) | 0.105 |
Troponin T (µg/L) | 0.01 (0−0.03) | 0 (0−0.03) | 0.02 (0−0.07) | < 0.001 |
Length of ICU stay (days) | 2 (1–5) | 2 (1–4) | 4 (12−7) | 0.001 |
Length of hospital stay (days) | 7 (4–13) | 8 (5–14) | 6 (3–11) | < 0.001 |
SpO2 Oxygen saturation, GCS Glasgow Coma Scale |
Compared with non-elderly TBI patients, elderly TBI patients were more commonly complicated with underlying diseases including hypertension (p < 0.001), coronary heart disease (p < 0.001) and diabetes mellitus (p = 0.038) (Table 2). The systolic blood pressure (139 vs 135, p = 0.023) was higher in elderly patients whereas diastolic blood pressure (62 vs 71, p < 0.001), heart rate (80 vs 89, p < 0.001) and body temperature (36.7 vs 36.9, p = 0.002) were all lower in elderly patients. Elderly patients had significantly higher GCS than non-elderly patients (14 vs 10, p = 0.016). And elderly patients were more likely to receive blood transfusion ((41.9% vs 26.8%, p = 0.003) and suffer arrhythmia (48% vs 22.3%, p < 0.001) during hospitalization. Moreover, the serum level of TnT was higher in elderly patients than non-elderly (0.01 vs 0, p = 0.014). While the in-hospital mortality did not significantly differ between elderly and non-elderly patients (20.3% vs 19.6%, p = 0.870).
Table 2
Baseline characteristics of non-elderly and elderly patients
Variables | Non-elderly (n = 112, 21.5%) | Elderly (n = 408, 78.5%) | p |
Age | 56 (47–61) | 82 (77–88) | < 0.001 |
Male gender | 85 (75.9%) | 194 (47.5%) | < 0.001 |
History of underlying disease | | | |
Hypertension | 49 (43.8%) | 279 (68.4%) | < 0.001 |
Coronary heart Disease | 8 (7.1%) | 122 (29.9%) | < 0.001 |
Acute myocardial infarction | 3 (2.7%) | 29 (7.1%) | 0.060 |
Diabetes mellitus | 20 (17.9%) | 111 (27.2%) | 0.038 |
Vital signs on admission | | | |
Systolic blood pressure | 135 (123–146) | 139 (129–149) | 0.023 |
Diastolic blood pressure | 71 (62–79) | 62 (56–69) | < 0.001 |
Heart rate | 89 (77–103) | 80 (68–90) | < 0.001 |
Respiratory rate | 18 (14–21) | 18 (15–21) | 0.918 |
Body temperature | 36.9 (36.3–37.7) | 36.7 (36.1–37.2) | 0.002 |
SpO2 (%) | 98.5 (97–100) | 98 (96.9–100) | 0.012 |
Pupillary reactivity | | | |
No-reaction (one side) | 4 (3.6%) | 22 (5.4%) | 0.416 |
No-reaction (both sides) | 3 (2.7%) | 11 (2.7%) | 1.000 |
GCS on admission | 10 (6–15) | 14 (8–15) | 0.016 |
Injury types | | | |
Concussion | 8 (7.1%) | 3 (0.7%) | < 0.001 |
Contusion | 4 (3.6%) | 11 (2.7%) | 0.541 |
Laceration | 24 (21.4%) | 51 (12.5%) | 0.022 |
Epidural hematoma | 4 (3.6%) | 10 (2.5%) | 0.513 |
Subdural hematoma | 46 (41.1%) | 227 (55.6%) | 0.006 |
Subarachnoid hemorrhage | 30 (26.8%) | 108 (26.5%) | 0.947 |
Intracerebral hematoma | 16 (14.3%) | 52 (12.7%) | 0.671 |
Operation | 23 (20.5%) | 110 (27%) | 0.160 |
Blood transfusion | 30 (26.8%) | 171 (41.9%) | 0.003 |
Arrhythmia during hospitalization | 25 (22.3%) | 196 (48%) | < 0.001 |
Troponin T | 0 (0−0.01) | 0.01 (0−0.04) | 0.014 |
Mortality | 22 (19.6%) | 83 (20.3%) | 0.870 |
Length of ICU stay (days) | 3 (2–6) | 2 (1–5) | 0.113 |
Length of hospital stay (days) | 7 (3–14) | 7 (5–13) | 0.155 |
SpO2 Oxygen saturation, GCS Glasgow Coma Scale |
Univariate Logistic Regression Analysis Of Risk Factors For Mortality
In overall included patients, history of acute myocardial infarction (OR = 2.548, p = 0.015), pupil no-reaction (OR = 2.805, p < 0.001), subarachnoid hemorrhage (OR = 1.601, p = 0.045), intracerebral hematoma (OR = 1.799, p = 0.044) and troponin T (OR = 2.541, p = 0.025) were positively associated poor outcome (Table 3). While body temperature (OR = 0.735, p = 0.011) and GCS (OR = 0.770, p < 0.001) were inversely correlated with poor outcome. In non-elderly patients, only pupil no-reaction (OR = 4.839. p < 0.001) and GCS (OR = 0.723. p < 0.001) were found related with in-hospital mortality (Table 4). And in elderly patients, coronary heart disease (OR = 1.869, p = 0.014), body temperature (OR = 0.692, p = 0.012), pupil no-reaction (OR = 2.398, p < 0.001), GCS (OR = 0.772, p < 0.001) and intracerebral hematoma (OR = 1.917, p = 0.048) and arrhythmia (OR = 1.640, p = 0.047) were significantly correlated with in-hospital mortality (Table 5).
Table 3
Univariate analysis of risk factors for mortality in overall patients
Variables | OR | 95%Cl | p |
age | 1.004 | 0.989–1.019 | 0.576 |
Male gender | 0.938 | 0.611–1.440 | 0.770 |
Hypertension | 1.096 | 0.701–1.713 | 0.689 |
Coronary heart Disease | 1.591 | 0.996–2.541 | 0.052 |
Acute myocardial infarction | 2.548 | 1.203–5.398 | 0.015 |
Diabetes mellitus | 1.320 | 0.820–2.124 | 0.253 |
Systolic blood pressure | 1.000 | 0.993–1.006 | 0.912 |
Diastolic blood pressure | 0.996 | 0.984–1.008 | 0.491 |
Heart rate | 0.998 | 0.986–1.010 | 0.769 |
Respiratory rate | 0.992 | 0.950–1.035 | 0.703 |
Body temperature | 0.735 | 0.581–0.931 | 0.011 |
SpO2 (%) | 0.987 | 0.935–1.041 | 0.623 |
Pupil no-reaction | 2.805 | 2.052–3.836 | < 0.001 |
GCS | 0.770 | 0.728–0.815 | < 0.001 |
Concussion | < 0.001 | - | 0.999 |
Contusion | 0.600 | 0.133–2.703 | 0.506 |
Laceration | 0.642 | 0.325–1.266 | 0.200 |
Epidural hematoma | 1.080 | 0.296–3.944 | 0.907 |
Subdural hematoma | 0.783 | 0.510–1.202 | 0.263 |
Subarachnoid hemorrhage | 1.601 | 1.010–2.538 | 0.045 |
Intracerebral hematoma | 1.799 | 1.015–3.189 | 0.044 |
Operation | 1.212 | 0.751–1.955 | 0.432 |
Blood transfusion | 1.073 | 0.693–1.663 | 0.751 |
Arrhythmia | 1.428 | 0.929–2.195 | 0.104 |
Troponin T | 2.541 | 1.123–5.752 | 0.025 |
OR Odds ratio, CI confidence interval, SpO2 Oxygen saturation, GCS Glasgow Coma Scale |
Table 4
Univariate analysis of risk factors for mortality in non-elderly patients
Variables | OR | 95%Cl | p |
age | 0.986 | 0.949–1.025 | 0.487 |
Male gender | 2.303 | 0.625–8.486 | 0.210 |
Hypertension | 0.865 | 0.336–2.229 | 0.765 |
Coronary heart Disease | < 0.001 | - | 0.999 |
Acute myocardial infarction | 8.9 | 0.769−103.029 | 0.080 |
Diabetes mellitus | 1.471 | 0.470–4.602 | 0.508 |
Systolic blood pressure | 0.995 | 0.982–1.008 | 0.459 |
Diastolic blood pressure | 0.993 | 0.970–1.015 | 0.519 |
Heart rate | 0.999 | 0.976–1.023 | 0.948 |
Respiratory rate | 1.005 | 0.923–1.094 | 0.909 |
Body temperature | 0.834 | 0.547–1.272 | 0.400 |
SpO2 (%) | 1.108 | 0.860–1.427 | 0.428 |
Pupil no-reaction | 4.839 | 2.429–9.641 | < 0.001 |
GCS | 0.723 | 0.621–0.842 | < 0.001 |
Concussion | < 0.001 | - | 0.999 |
Contusion | < 0.001 | - | 0.999 |
Laceration | 1.099 | 0.359–3.363 | 0.868 |
Epidural hematoma | 4.400 | 0.584–33.142 | 0.150 |
Subdural hematoma | 1.250 | 0.489–3.197 | 0.641 |
Subarachnoid hemorrhage | 1.359 | 0.493–3.749 | 0.553 |
Intracerebral hematoma | 1.444 | 0.417–5.003 | 0.562 |
Operation | 2.158 | 0.757–6.151 | 0.150 |
Blood transfusion | 1.359 | 0.493–3.749 | 0.553 |
Arrhythmia | 0.730 | 0.222–2.396 | 0.604 |
Troponin T | 2.228 | 0.791–6.278 | 0.130 |
OR Odds ratio, CI confidence interval, SpO2 Oxygen saturation, GCS Glasgow Coma Scale |
Table 5
Univariate analysis of risk factors for mortality in elderly patients
Variables | OR | 95%Cl | p |
age | 1.027 | 0.992–1.062 | 0.128 |
Male gender | 0.81 | 0.498–1.316 | 0.394 |
Hypertension | 1.173 | 0.692–1.990 | 0.553 |
Coronary heart Disease | 1.869 | 1.132–3.085 | 0.014 |
Acute myocardial infarction | 2.206 | 0.984–4.945 | 0.055 |
Diabetes mellitus | 1.288 | 0.761–2.179 | 0.345 |
Systolic blood pressure | 1.001 | 0.993–1.009 | 0.777 |
Diastolic blood pressure | 0.997 | 0.983–1.011 | 0.708 |
Heart rate | 0.998 | 0.984–1.012 | 0.787 |
Respiratory rate | 0.987 | 0.939–1.038 | 0.619 |
Body temperature | 0.692 | 0.519–0.922 | 0.012 |
SpO2 (%) | 0.981 | 0.929–1.036 | 0.488 |
Pupil no-reaction | 2.398 | 1.673–3.437 | < 0.001 |
GCS | 0.772 | 0.725–0.823 | < 0.001 |
Concussion | < 0.001 | - | 0.999 |
Contusion | 0.867 | 0.184–4.091 | 0.857 |
Laceration | 0.485 | 0.199–1.179 | 0.110 |
Epidural hematoma | 0.428 | 0.053–3.428 | 0.424 |
Subdural hematoma | 0.686 | 0.423–1.113 | 0.127 |
Subarachnoid hemorrhage | 1.672 | 0.997–2.806 | 0.051 |
Intracerebral hematoma | 1.917 | 1.005–3.658 | 0.048 |
Operation | 1.049 | 0.611–1.799 | 0.863 |
Blood transfusion | 1.013 | 0.622–1.651 | 0.958 |
Arrhythmia | 1.640 | 1.008–2.670 | 0.047 |
Troponin T | 3.168 | 0.902–11.124 | 0.072 |
OR Odds ratio, CI confidence interval, SpO2 Oxygen saturation, GCS Glasgow Coma Scale |
Association Between Troponin T And Outcome After Adjusting Confounders
To verify the independent association between troponin T and outcome, multivariate logistic regression analyses were performed in overall patients and two subgroups (age < 65, age ≥ 65). After adjusting the confounding effects of acute myocardial infarction, body temperature, pupil no-reaction, GCS, subarachnoid hemorrhage, intracerebral hematoma, the OR of troponin T was 1.909 without statistical significance (p = 0.143) in overall included patients (Table 6). While in patients < 65 years old, the OR of troponin T was 3.178 with statistical significance (p = 0.040) after adjusting the confounding effects of pupil no-reaction, GCS. However, level of troponin T was not significantly associated with outcome in patients whose age ≥ 65 (OR = 1.839, p = 0.456), after considering the effects of confounders including coronary heart disease, body temperature, pupil no-reaction, GCS, intracerebral hematoma and arrhythmia.
Table 6
Association between troponin T and mortality after adjusting confounders in overall patients and subgroups
| OR | 95%Cl | p |
Overall patients* | 1.909 | 0.803–4.536 | 0.143 |
< 65 years old** | 3.178 | 1.057–9.562 | 0.040 |
≥ 65 years old# | 1.839 | 0.371–9.113 | 0.456 |
* adjusted for acute myocardial infarction, body temperature, pupil no-reaction, GCS, subarachnoid hemorrhage, intracerebral hematoma. ** adjusted for pupil no-reaction, GCS. # adjusted for coronary heart disease, body temperature, pupil no-reaction, GCS, intracerebral hematoma, arrhythmia. OR Odds ratio, CI confidence interval |
Prognostic value of troponin T in overall patients and subgroups
The AUC value of troponin T and GCS for predicting mortality of overall patients was 0.644 and 0.794, respectively (Table 7) (Fig. 2A). GCS had significantly higher AUC value than troponin T (Z = 3.6939, p < 0.05). Combining troponin T could not improve the predictive value of single assessment of GCS (0.814 vs 0.794, Z = 0.6006, p > 0.05). For those age < 65, the AUC value of troponin T and GCS was 0.693 and 0.829, respectively (Fig. 2B). Troponin had comparable AUC value with GCS (Z = 1.5804, p > 0.05). The AUC value of combining troponin T with GCS was 0.862, which was higher than single GCS, though without statistical significance (Z = 0.4568, p > 0.05). However, the AUC value of combining troponin T with GCS was significantly higher than single evaluation of troponin T (Z = 2.0505, p < 0.05). For those age ≥ 65, the AUC value of troponin T was 0.632 (Fig. 2C), which was significantly lower than 0.793 of GCS (Z = 3.5778, p < 0.05). Combining troponin T with GCS could not improve the predictive value of single GCS (Z = 0.5260, p > 0.05). A remarkable discovery was that combining troponin T could distinctly improve the sensitivity of predicting mortality.
Table 7
Prognostic value of troponin T and GCS in overall patients and subgroups
| AUC | 95%Cl | Sensitivity | Specificity |
Overall patients | | | | |
TnT | 0.644 | 0.582–0.706 | 0.590 | 0.687 |
GCS | 0.794 | 0.746–0.842 | 0.747 | 0.733 |
GCS + TnT | 0.814 | 0.770–0.858 | 0.867 | 0.617 |
Patients < 65 years old | | | | |
TnT | 0.693 | 0.562–0.824 | 0.500 | 0.833 |
GCS | 0.829 | 0.723–0.934 | 0.833 | 0.818 |
GCS + TnT | 0.862 | 0.768–0.955 | 0.864 | 0.822 |
Patients ≥ 65 years old | | | | |
TnT | 0.632 | 0.562–0.703 | 0.614 | 0.646 |
GCS | 0.793 | 0.739–0.847 | 0.778 | 0.699 |
GCS + TnT | 0.812 | 0.764–0.860 | 0.855 | 0.652 |
AUC area under the receiver operating characteristics curve, CI confidence interval, TnT troponin T, GCS Glasgow Coma Scale |