Association between apolipoprotein E genotype and outcome of traumatic brain injury

Abstract

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 after 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.