Association between apolipoprotein E genotype and outcome of traumatic brain injury

Background. The prognosis of traumatic brain injury is quite variable and not fully explained by the known factors. This study is to examine if the polymorphism of apolipoprotein E (apoE) influences the outcome of traumatic brain injury. Methods. Over a period of twelve months, we prospectively studied 100 patients who sustained traumatic brain injuries and were admitted to our neurosurgical unit. Findings. Nineteen patients were apoE4(+) and 81 patients were apoE4(-). There was no significant difference between apoE4(+) and apoE4(-) groups in the cause of injury (p=0.288), type of brain injury (p=0.983) and choice of treatment (p=0.88). The proportion of patients with a lower GCS (<13), indicating a poor prognosis, was higher in the apoE4(+) group (73.7%) than that in apoE4(-) group (61.7%), although the difference was not significant (p=0.654). Six patients (7.4%) in the apoE4(-) group and 5(26.3%) in the apoE4(+) group had been drinking alcohol at the time of injury (p=0.018). The mean duration of hospital stay for apoE4(+) patients was significantly longer than for apoE4(-) patients (p<0.001). Six months after injury, 10 of 19 patients (52.6%) with apoE4 had an unfavorable outcome (dead, vegetative state, or severe disability) compared with 20 of the 81 (24.1%) patients without apoE4 (p=0.017). The apoE4(+) patients had a significantly longer hospital stay and unfavorable outcomes a er brain injury. Interpretation. This study discloses a significant genetic association between the apoE genotypes and outcomes of traumatic brain injury. Patients with apoE4 allele are more likely to have an unfavorable clinical outcome after brain injury.