Apolipoprotein E polymorphism and gender difference in outcome after severe traumatic brain injury

Background: Traumatic brain injury (TBI) is one of the most common causes of death and dismal outcome among children and young adults. The morbidity and mortality differ but more aggressive monitoring and more designated neuro intensive care units have improved the results. Studies have demonstrated a connection between apolipoprotein E (APOE) genotype and outcome after TBI, but few are prospective and none is from northern Europe. APOE has three alleles: epsilon 2, epsilon 3 and epsilon 4. Methods: A total of 96 patients with Glasgow coma score (GCS) <= 8 were prospectively and consecutively included. APOE genotypes were all analyzed at the same laboratory from blood samples by polymerase chain reaction-restriction fragment length polymorphism. Results: All patients were assessed at 1 year with Glasgow outcome scale extended (GOSE), National Institute of Health Stroke Scale (NIHSS) and the Barthel daily living index. The genotype was available in all patients. Twenty-six patients expressed APOE epsilon 4 while 70 patients did not. Outcome demonstrated that patients with APOE epsilon 4 had worse outcome vs. those lacking this allele. When subdividing patients into gender, males with APOE epsilon 4 did worse, a difference not detected among female patients. Conclusions: APOE epsilon 4 correlated to worse outcome in TBI patients. We also found that males with APOE epsilon 4 had poor outcome while females did not. Thus, the results indicate that genetic polymorphism may influence outcome after TBI.