Previous preliminary studies have suggested that possession of the
APOE epsilon4 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 epsilon4 carriers having an unfavourable outcome compared with 33% of non-carriers of
APOE epsilon4. However, there was evidence of an interaction between age and
APOE genotype on outcome (P = 0.007) such that possession of
APOE epsilon4 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 <15 years, carriage of
APOE epsilon4 being equivalent to ageing by 25 years. This finding is consistent with experimental data suggesting that the effect of
APOE genotype on outcome after
head injury may be expressed through the processes of repair and recovery.