The association between APOE ε4, age and outcome after head injury: a prospective cohort study

Previous preliminary studies have suggested that possession of the APOE ε4 allele is associated with a poor outcome after head injury. This study was designed to confirm and extend those observations in a larger study with examination of additional variables. We prospectively identified admissions to a Neurosurgical Unit for head injury, collected demographic and clinical data, determined APOE genotypes and obtained follow-up information at 6 months. A total of 1094 subjects were enrolled (age range: 0–93 years, mean 37 years). Outcome was assessed using the Glasgow Outcome Scale. There was no overall association between APOE genotype and outcome, with 36% of APOE ε4 carriers having an unfavourable outcome compared with 33% of non-carriers of APOE ε4. However, there was evidence of an interaction between age and APOE genotype on outcome (P = 0.007) such that possession of APOE ε4 reduced the prospect of a favourable outcome in children and young adults. The influence of APOE genotype in younger patients after head injury can be expressed as, at age