Abstract

Background: The aim of this study was to assess the effect of Vitamins C and E on mortality, intensive care unit (ICU) length of stay, and Glasgow Outcome Scale-Extended (GOS-E) score of traumatic brain injury (TBI) patients.

Methods: Using data from records of patients in a retrospective cohort study, we included 1321 TBI patients, 269 treated and 1052 untreated, aged over 18 years with information on exposure (i.e., Vitamins C and E) and confounders. Age, Glasgow Coma Scale, pupil status, Rotterdam classification, blood sugar, blood pressure, international normalized ratio, and comorbidity of patients were considered as the confounding factors. Endpoints were GOS-E on follow-up, mortality, and ICU length of stay. Propensity score matching was performed to adjust the confounders.

Results: Based on the average treatment effect estimates, the use of Vitamins C and E reduced the risk of mortality (risk difference [RD]: −0.07; 95% confidence interval [CI]: −0.14–−0.003) and reduced the length of ICU stay (RD -1.77 95% CI:-3.71-0.16). Furthermore, our results showed that GOS-E was improved significantly (RD: 0.09, 95% CI : 0.03-0.16).

Conclusion: Our study suggests that using Vitamins C and E could decrease mortality and length of ICU stay and improve the GOS-E score and functions of the patients with severe TBI. As they are safe and inexpensive medications, they can be used in routine practice in ICUs to improve the outcomes of TBI patients.

Keywords: Ascorbic acid, Traumatic brain injury, TBI, Vitamin C, Vitamin E

INTRODUCTION

Traumatic brain injury (TBI) is an acute injury to the skull caused by external sources that can be classified into mild, moderate, and severe according to the patient’s condition.[ 6 , 15 ] Every year, TBI leads to 2.8 million emergency room visits, admissions, and deaths, imposing a cost of approximately 80 billion dollars on society.[ 17 , 34 ] Falling, objects, and vehicle accidents are the most common mechanisms of TBI in the USA between 2007 and 2013 (413.2, 142.1, and 121.7 events of TBI and age adjusted, respectively).[ 46 ] Computed tomography (CT scan) is the main modality used to evaluate the severity of injury.[ 42 ] Severe TBI carries a 30% mortality risk, and roughly half of the patients with moderate or severe TBI regain their independence.[ 27 , 36 ] Based on the severity of the insult, different surgical and medical treatments may be needed to diminish the burden of the damage to the brain.[ 36 ] There have been numerous reports of medical interventions to accelerate the prognostic improvement of patients, including corticosteroids, erythropoietin, and magnesium.[ 3 , 40 , 41 ] Recently, Vitamins C and E have been administered in patients with TBI to investigate the clinical outcomes of patients.[ 37 ] Ascorbic acid (AA) plays a crucial role in reducing oxidative stress besides being a cofactor in many reactions, and its concentration is 80 times higher in brain cells compared to the plasma fluid. This indicates the importance of AA for maintaining the function of the central nervous system.[ 18 , 21 , 25 , 38 ] Vitamin E is a fat-soluble agent and a part of the tocopherols and tocotrienols families which are shown to have significant antioxidative effects, inhibitory effects on lipoprotein oxidation, and anti-inflammatory and platelet anti-aggregation features.[ 2 , 8 , 24 ] Furthermore, evidence shows the neuroprotective effect of this vitamin and its role in nervous system development in addition to the aforementioned effects.[ 10 , 19 ] Given the scarcity of evidence on the effect of Vitamins C and E on the outcomes of patients with TBI and the remarkable primary outcomes of the present studies,[ 25 , 37 ] we aimed to examine the above-mentioned outcomes of severe TBI patients following administration of combined Vitamins C and E in a large-scale cohort.

MATERIALS AND METHODS

This study was a retrospective cohort and was prepared according to the Strengthening the Reporting of Observational Studies in Epidemiology guideline.[ 47 ] We collected records of all patients admitted to the emergency room of the tertiary trauma center, affiliated with Shiraz University of Medical Sciences, who suffered a TBI between 2017 and 2021, and followed until the time of discharge from the hospital. The patients with early death, within 2 days after surgery, were excluded from this study. Then, based on the Abbreviated Injury Scale (AIS)-head, we isolated severe TBI patients from others.[ 16 ] Severe TBI was defined as AIS-head more than and equal to 3 without AIS more than 3 in other regions. As there was no unique protocol for the prescription of these two vitamins, based on the clinical judgment of physicians, some patients received these supplements and others did not. Furthermore, for some periods of time, the medication shortage was considerable. These issues divided the patients into treated and untreated groups. Propensity score matching (PSM) was performed on the entire cohort to include a sample of matched patients from both treated and untreated patients. Baseline characteristics (including demographic features, Glasgow Coma Scale (GCS), pupil status, Rotterdam classification, blood sugar and systolic blood pressure on arrival, international normalized ratio, and comorbidities) along with measures such as duration of hospital and intensive care unit (ICU) stay and Glasgow Outcome Scale-Extended (GOS-E) and prescription of combined Vitamins C and E extracted from documents. The exposure was receiving Vitamins C and E, and the outcomes were follow-up GOS-E on follow-up, mortality, and ICU length of stay in patients who survived.

We considered the follow-up time for the GOS-E score to be 6 months after discharge from the hospital. Given the availability of these drugs in our hospital and the expert opinion of attending physicians regarding the patients’ conditions, Vitamins C and E were prescribed. The prescribed dosage of Vitamins C and E in the ICU setting was 3 days of intravenous administration of both vitamin C (500 mg) and vitamin E (100 units) started within 5 days after TBI.

Statistical analysis

We performed PSM using a logistic regression model to balance the potential confounders, including the admission age, GCS on arrival (motor part), pupil condition, Rotterdam CT classification, blood sugar, systolic blood pressure, international normalized ratio, and preexisting comorbidities condition (i.e., diabetes, hypertension, and other cardiovascular diseases), between treated and untreated patients. We assessed PS matching (one to many matching) between treated and untreated patients using a caliper of 0.05, meaning that the PS could have varied by 5% for the two members of a matched set.[ 5 , 14 ] Furthermore, we used the standardized mean difference (SMD) to evaluate the adequacy of no major imbalance for the measured potential confounders; an SMD of 10% or less, as a general rule, has been indicated as a sufficient balance on the confounders.[ 20 , 26 ]

After PS matching, we estimated the average treatment effect (ATE) using the risk difference (RD) for the outcome of interest, and the 95% confidence intervals (CIs) were derived using robust standard error.

Ethics

The ethics committee of Shiraz University of Medical Sciences approved this study to be conducted with registry number IR sums.med.rec.1400.600.

RESULTS

Among the total of 1321 patients included in the study, we identified 269 (20.36%) patients treated with Vitamins C and E. The baseline characteristics of patients treated and untreated with Vitamins C and E are presented in Table 1 .

Table 1:

Baseline characteristics of patients treated and untreated with Vitamins C and E.

The median (interquartile range [IQR]) age of the patients untreated and treated with C and E at the entry into the study was 31 (IQR: 23–50) and 34 years (IQR: 24–50). Patients who were untreated with Vitamins C and E were more likely to be dead, with a lower rate of cardiovascular diseases (except hypertension such as heart failure and ischemic heart disease) and hypertension, but they had a higher international normalized ratio score [ Table 1 ].

Figure 1 shows the distribution of the estimated propensity score in the patients untreated and treated with Vitamins C and E. Those who were treated with Vitamins C and E had, on average, a greater estimated probability of receiving Vitamins C and E (0.18) than those who did not receive them (0.21). After matching, SMD indicates no major imbalance on confounders in the propensity-matched cohort ( Table 2 ; SMD all ≤0.1, a sufficient balance on the confounders).

Figure 1:

Distribution of the estimated propensity score in patients untreated and treated with Vitamins C and E.

Table 2:

Standardized mean difference for the confounders in matched data.

Based on ATE estimates, the use of Vitamins C and E reduced the risk of mortality (RD: −0.07; 95% CI: −0.14–−0.003) and reduced the ICU length of stay (RD: −1.77; 95% CI: −3.71–0.16). Furthermore, our results showed that GOS-E was improved significantly (RD: 0.09, 95% CI : 0.03-0.16).

DISCUSSION

To the best of our knowledge, this is the first study with a large number of patients and PSM that investigates the effect of Vitamins C and E on clinical outcomes of TBI patients.

Our results showed that Vitamins C and E could remarkably reduce the risk of mortality and ICU length of stay and help improve the GOS-E score of patients as a clinical outcome index.

Corticosteroid Randomization after Significant Head Injury and the International Mission for Prognosis and Analysis of Clinical Trials in TBI are two models that were developed in 2008 for the prediction of TBI patients’ prognosis.[ 32 , 44 ] These models suggested the country, age, GCS, the status of pupils, extracranial injury, CT findings, hypoxia, hypotension, Marshall CT grade, glucose, and hemoglobin concentration as prognostic factors. Among the mentioned prognostic factors, GCS on admission is regarded as the most important one, in a way that patients with GCS <8 have a 30% risk of mortality.

By taking these factors into account, as we wanted to divide the patients into cases and controls, we considered the abovementioned baseline characteristic as a cofounder of our study and performed a PSM to eliminate systematic differences. Originally introduced by Rosenbaum and Rubin in 1983, PSM is a technique for ensuring that in observational studies, the distributions of baseline covariates are approximately the same for both treatment and control groups. Based on the similar characteristics of these two groups, a setting that mimics randomized clinical trials is simulated.[ 4 ]

Preclinical studies on animal models demonstrated that Vitamin C could decrease the mortality rate in rats with hypoxic brain damage and vasospasm following subarachnoid hemorrhage. Three out of four studies that evaluated the effect of Vitamin C on TBI in rats[ 25 ] concluded that AA could significantly improve the functions of rats;[ 29 , 30 , 48 ] another study showed that survival of rats was increased after a supplementary dose of Vitamin C.[ 23 ] Furthermore, Lin et al. observed that disruption of the blood–brain barrier (BBB) was decreased following the administration of Vitamin C.[ 29 ]

The only clinical study was carried out by Razmkon et al. During this double-blinded controlled trial, they administrated low (500 mg/day for 7 days intravenously) and high (10 g/day for the 1^st and 4^th days and 4 g/day for other 3 days) doses of Vitamin C. Patients with a head injury, GCS under 8, and radiology imaging in favor of diffuse axonal injury were included and significant renal or liver failure, glucose-6-phosphate dehydrogenase deficiency (G6PDD), and previous central nervous system lesions were the exclusion criteria. Duration of hospital stay (29.7% vs. 26.9% and 30.4% in low dose and high dose of Vitamin C, respectively) and mortality rate (29.7% vs. 34.6% and 30.4% in low dose and high dose of Vitamin C, respectively) were not significantly different between the control group and the patients who were administrated Vitamin C. Interestingly, perilesional edema was stable or reduced in 68% of patients receiving a high dose of Vitamin C.[ 37 ] These results were in contrast with ours in that we observed decreased mortality of patients receiving combined Vitamins E and C and significantly shorter hospital stay in the treatment group.

There was some difference, regardless of design, between our study and Razmkon’s study that is worth mentioning. To begin with, our study had a sample size 13-fold greater than this study. Second, although this study included a control group of patients, the controls were not matched to the treatment arm in terms of confounding factors. Third, the severe patients have been defined by Razmkon et al. as patients with a GCS score of less than 8 while our study considered patients with AIS-head more than and equal to 3 without AIS more than 3 in other regions. Last but not least, there was a difference in vitamin dosage. The dose of Vitamins C and E in our study was similar to the low dose of Vitamin C and Vitamin E in the Razmkon et al. study, but they prescribed these two drugs separately for 7 days, and we administered them simultaneously for 3 days.

The role of Vitamin E has been described as a booster of cognitive disturbance improvement following TBI.[ 11 , 13 ] Animal studies showed promising outcomes following the administration of Vitamin E. In a study on pigs, Vitamin E led to attenuation of brain tissue damage.[ 22 ] Studies on rats revealed more interesting outcomes. Vitamin E improved the survival and neurocognitive and motor functions and decreased brain edema, inflammation, necrosis, and histological damage following induction of TBI.[ 2 , 9 , 49 ] The study carried out by Razmkon et al. was the only clinical study that administrated 400 IU/day for 7 days in previously discussed patients. Their results revealed a lower mortality rate (16.7% vs. 29.7%) and significantly better GOS score at discharge time compared to the control group.[ 37 ] These outcomes were congruent with what we observed (P = 0.04). As our center is the focal referral point of TBI in the south of Iran, we have included a large scale of patients with diverse baseline characteristics. This diversity would be helpful in the generalization of the results of this study.

Mechanism and rationale for administration of Vitamins C and E

In traumatic brain injuries and the following secondary insults, oxidative stress and release of free radicals are significantly increased.[ 28 ] In such situations, the antioxidative nature of AA and Vitamin E encounters the cascades. The proof for this has been illustrated in Polidori et al. and Brau et al.’s studies. These two studies showed that after the brain insult, the concentration of AA decreased in both plasma and cerebrospinal fluid.[ 7 , 35 ] Furthermore, after trauma, the integrity of the BBB will be disturbed, leading to the migration of the leukocytes, the release of cytotoxic agents, free radicals, and the expansion of the inflammation to intact areas. Thus, it is important to maintain the integrity of BBB.[ 43 ] Vitamin C has been proven to stabilize the integrity of BBB in TBI.[ 28 ] Vitamin E is a critical cell membrane unit that acts as an antioxidative agent and peroxidative of lipids. Vitamin C restores the function of oxidized Vitamin E;[ 12 , 33 , 45 ] this justifies the administration of Vitamin C and coadministration of Vitamin E.

Costs and adverse effects

To speak economically, it has been reported that supplementary administration of AA during pregnancy will cost about 20$, and monthly administration of Vitamin E costs 5$.[ 39 , 50 ] Although the route of administration in our study differed from these two reported studies, it reflects how low the costs are. The most serious adverse effects of Vitamin C are nausea, vomiting, headache, and flushing and it is contraindicated in G6PDD, thalassemia, and hemochromatosis.[ 1 ] Except for allergy, no contraindication was reported for Vitamin E, and nausea, vomiting, gastrointestinal upset, increase in serum creatinine, and inhibition of platelet aggregation are the common side effect.[ 31 ] Overall, both these vitamins are safe and inexpensive.

Limitation

Our study was limited by the unavailability of these two vitamins in our center. The retrospective nature of our study and being conducted in a single center are the other limitations. Since we estimated the effect of Vitamins C and E from an observational study, instead of a well-defined randomized clinical trial, some unknown confounders might have also distorted our results.

CONCLUSION

Our study suggests that administering Vitamins C and E may decrease the mortality and length of ICU stay and improve the GOS-E score and functions of the patients with severe TBI. This study suggests that these two vitamins may have neuroprotective effects. Besides the fact that they are safe and inexpensive, they can be used in routine practice to decrease the burden of TBI on the patients. For consolidation of our results, further randomized clinical trials with different doses and both separate and combined administration of Vitamins C and E are needed.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship

Publication of this article was made possible by the James I. and Carolyn R. Ausman Educational Foundation.

Conflicts of interest

There are no conflicts of interest.

Disclaimer

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.

References

1. Abdullah M, Attia FN, editors. Vitamin C (Ascorbic Acid). StatPearls. Treasure Island: StatPearls Publishing; 2022. p. Available from: https://www.ncbi.nlm.nih.gov/books/NBK499877 [Last accessed on 2021 Jun 15]

2. Aiguo W, Zhe Y, Gomez-Pinilla F. Vitamin E protects against oxidative damage and learning disability after mild traumatic brain injury in rats. Neurorehabil Neural Repair. 2010. 24: 290-8

3. Arango MF, Bainbridge D, editors. Magnesium for acute traumatic brain injury. Cochrane Database Syst Rev. 2008. p. Cd005400

4. Austin PC. An introduction to propensity score methods for reducing the effects of confounding in observational studies. Multivariate Behav Res. 2011. 46: 399-424

5. Austin PC. Optimal caliper widths for propensity-score matching when estimating differences in means and differences in proportions in observational studies. Pharm Stat. 2011. 10: 150-61

6. Balestreri M, Czosnyka M, Chatfield DA, Steiner LA, Schmidt EA, Smielewski P. Predictive value of Glasgow Coma Scale after brain trauma: Change in trend over the past ten years. J Neurol Neurosurg Psychiatry. 2004. 75: 161-2

7. Brau RH, García-Castiñeiras S, Rifkinson N. Cerebrospinal fluid ascorbic acid levels in neurological disorders. Neurosurgery. 1984. 14: 142-6

8. Clarke MW, Burnett JR, Croft KD. Vitamin E in human health and disease. Crit Rev Clin Lab Sci. 2008. 45: 417-50

9. Clifton GL, Lyeth BG, Jenkins LW, Taft WC, DeLorenzo RJ, Hayes RL. Effect of D, alpha-tocopheryl succinate and polyethylene glycol on performance tests after fluid percussion brain injury. J Neurotrauma. 1989. 6: 71-81

10. Comitato R, Ambra R, Virgili F. Tocotrienols: A family of molecules with specific biological activities. Antioxidants (Basel). 2017. 6: 93

11. Conte V, Uryu K, Fujimoto S, Yao Y, Rokach J, Longhi L. Vitamin E reduces amyloidosis and improves cognitive function in Tg2576 mice following repetitive concussive brain injury. J Neurochem. 2004. 90: 758-64

12. Di Pietro V, Yakoub KM, Caruso G, Lazzarino G, Signoretti S, Barbey AK. Antioxidant therapies in traumatic brain injury. Antioxidants (Basel). 2020. 9: 260

13. Dobrovolny J, Smrcka M, Bienertova-Vasku J. Therapeutic potential of Vitamin E and its derivatives in traumatic brain injury-associated dementia. Neurol Sci. 2018. 39: 989-98

14. Etminan M, Nazemipour M, Mansournia MA, Candidate MS. Potential biases in studies of acid-suppressing drugs and COVID-19 infection. Gastroenterology. 2021. 160: 1443-6

15. Gardner AJ, Zafonte R, Aminoff MJ, Boller F, Swaab DF, editors. Neuroepidemiology of traumatic brain injury. Handbook of Clinical Neurology. Ch. 12. Netherlands: Elsevier; 2016. p. 207-23

16. Gennarelli TA, Wodzin E. AIS 2005: A contemporary injury scale. Injury. 2006. 37: 1083-91

17. Gooch CL, Pracht E, Borenstein AR. The burden of neurological disease in the United States: A summary report and call to action. Ann Neurol. 2017. 81: 479-84

18. Harrison FE, May JM. Vitamin C function in the brain: Vital role of the ascorbate transporter SVCT2. Free Radic Biol Med. 2009. 46: 719-30

19. Head B, Du JL, Tanguay R, Kioussi C, Traber M. Vitamin E is necessary to protect neural crest cells in developing zebrafish embryos. Curr Dev Nutr. 2020. 4: 1209

20. Hernán MA, Robins JM, editors. Causal Inference: What if, Boca Raton: Chapman and Hall/CRC. 2020. p.

21. Hill A, Wendt S, Benstoem C, Neubauer C, Meybohm P, Langlois P. Vitamin C to improve organ dysfunction in cardiac surgery patients-review and pragmatic approach. Nutrients. 2018. 10: 974

22. Inci S, Ozcan OE, Kilinç K. Time-level relationship for lipid peroxidation and the protective effect of alpha-tocopherol in experimental mild and severe brain injury. Neurosurgery. 1998. 43: 330-5 discussion 335-6

23. Ishaq GM, Saidu Y, Bilbis LS, Muhammad SA, Jinjir N, Shehu BB. Effects of α-tocopherol and ascorbic acid in the severity and management of traumatic brain injury in albino rats. J Neurosci Rural Pract. 2013. 4: 292-7

24. Jiang Q. Natural forms of Vitamin E: Metabolism, antioxidant, and anti-inflammatory activities and their role in disease prevention and therapy. Free Radic Biol Med. 2014. 72: 76-90

25. Kangisser L, Tan E, Bellomo R, Deane AM, Plummer MP. Neuroprotective properties of Vitamin C: A scoping review of pre-clinical and clinical studies. J Neurotrauma. 2021. 38: 2194-205

26. Khodamoradi F, Nazemipour M, Mansournia N, Yazdani K, Khalili D, Mansournia MA. The effects of smoking on metabolic syndrome and its components using causal methods in the Iranian population. Int J Prev Med. 2021. 12: 118

27. Kowalski RG, Hammond FM, Weintraub AH, Nakase-Richardson R, Zafonte RD, Whyte J. Recovery of consciousness and functional outcome in moderate and severe traumatic brain injury. JAMA Neurol. 2021. 78: 548-57

28. Leichtle SW, Sarma AK, Strein M, Yajnik V, Rivet D, Sima A. High-dose intravenous ascorbic acid: Ready for prime time in traumatic brain injury?. Neurocrit Care. 2020. 32: 333-9

29. Lin JL, Huang YH, Shen YC, Huang HC, Liu PH. Ascorbic acid prevents blood-brain barrier disruption and sensory deficit caused by sustained compression of primary somatosensory cortex. J Cereb Blood Flow Metab. 2010. 30: 1121-36

30. Maekawa T, Uchida T, Nakata-Horiuchi Y, Kobayashi H, Kawauchi S, Kinoshita M. Oral ascorbic acid 2-glucoside prevents coordination disorder induced via laser-induced shock waves in rat brain. PLoS One. 2020. 15: e0230774

31. Medina JG. Vitamin E. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557737 [Last accessed on 2022 Jan ???].

32. Perel P, Arango M, Clayton T, Edwards P, Komolafe E. Predicting outcome after traumatic brain injury: Practical prognostic models based on large cohort of international patients. BMJ. 2008. 336: 425-9

33. Pérez-Rodríguez L, Redondo T, Ruiz-Mata R, Camacho C, Moreno-Rueda G, Potti J. Vitamin E supplementation-but not induced oxidative stress-influences telomere dynamics during early development in wild passerines. Front Ecol Evol. 2019. 7:

34. Peterson ABXu LDaugherty JBreiding MJ. Surveillance Report of Traumatic Brain Injury-Related Emergency Department Visits, Hospitalizations, and Deaths, United States, 2014. Available from: https://www.cdc.gov/traumaticbraininjury/pdf/TBI-Surveillance-Report-FINAL_508.pdf [Last accessed on 2022 Oct 09].

35. Polidori MC, Mecocci P, Frei B. Plasma Vitamin C levels are decreased and correlated with brain damage in patients with intracranial hemorrhage or head trauma. Stroke. 2001. 32: 898-902

36. Rajajee V, Moreira ME, Rabinstein AA, editors. Management of Acute Moderate and Severe Traumatic Brain Injury. Waltham: Up to Date. 2019. p.

37. Razmkon A, Sadidi A, Sherafat-Kazemzadeh E, Mehrafshan A, Jamali M, Malekpour B. Administration of Vitamin C and Vitamin E in severe head injury: A randomized double-blind controlled trial. Clin Neurosurg. 2011. 58: 133-7

38. Rice ME, Lee EJ, Choy Y. High levels of ascorbic acid, not glutathione, in the CNS of anoxia-tolerant reptiles contrasted with levels in anoxia-intolerant species. J Neurochem. 1995. 64: 1790-9

39. Richard B. ALSUntangled 55: Vitamin E (α-tocopherol). Amyotroph Lateral Scler Frontotemporal Degener. 2021. 22: 154-60

40. Roberts I, Yates D, Sandercock P, Farrell B, Wasserberg J, Lomas G. Effect of intravenous corticosteroids on death within 14 days in 10008 adults with clinically significant head injury (MRC CRASH trial): Randomised placebo-controlled trial. Lancet. 2004. 364: 1321-8

41. Robertson CS, Hannay HJ, Yamal JM, Gopinath S, Goodman JC, Tilley BC. Effect of erythropoietin and transfusion threshold on neurological recovery after traumatic brain injury: A randomized clinical trial. JAMA. 2014. 312: 36-47

42. Servadei F, Murray GD, Penny K, Teasdale GM, Dearden M, Iannotti F. The value of the “worst” computed tomographic scan in clinical studies of moderate and severe head injury. European brain injury consortium. Neurosurgery. 2000. 46: 70-5 discussion 75-77

43. Sivandzade F, Alqahtani F, Cucullo L. Traumatic brain injury and blood-brain barrier (BBB): Underlying pathophysiological mechanisms and the influence of cigarette smoking as a premorbid condition. Int J Mol Sci. 2020. 21: 2721

44. Steyerberg EW, Mushkudiani N, Perel P, Butcher I, Lu J, McHugh GS. Predicting outcome after traumatic brain injury: Development and international validation of prognostic scores based on admission characteristics. PLoS Med. 2008. 5: e165 discussion e165

45. Surai PF, editors. Natural Antioxidants in Avian Nutrition and Reproduction: Nottingham: Nottingham University Press. 2002. p.

46. Taylor CA, Bell JM, Breiding MJ, Xu L. Traumatic brain injury-related emergency department visits, hospitalizations, and deaths-United States, 2007 and 2013. MMWR Surveill Summ. 2017. 66: 1-16

47. Vandenbroucke JP, von Elm E, Altman DG, Gøtzsche PC, Mulrow CD, Pocock SJ. Strengthening the reporting of observational studies in epidemiology (STROBE): Explanation and elaboration. PLoS Med. 2007. 4: e297

48. Wang KW, Wang HK, Chen HJ, Liliang PC, Liang CL, Tsai YD. Simvastatin combined with antioxidant attenuates the cerebral vascular endothelial inflammatory response in a rat traumatic brain injury. BioMed Res Int. 2014. 2014: 910260

49. Yang J, Han Y, Ye W, Liu F, Zhuang K, Wu G. Alpha tocopherol treatment reduces the expression of Nogo-A and NgR in rat brain after traumatic brain injury. J Surg Res. 2013. 182: e69-77

50. Yieh L, McEvoy CT, Hoffman SW, Caughey AB, MacDonald KD, Dukhovny D. Cost effectiveness of vitamin c supplementation for pregnant smokers to improve offspring lung function at birth and reduce childhood wheeze/asthma. J Perinatol. 2018. 38: 820-7