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Background: Existing evidence suggests that some patients who sustain a head injury suffer cognitive decline many years later, and that head injury and possession of the APOE ε4 allele are each risk factors for Alzheimer's disease.
Objective: To determine whether late cognitive decline after head injury is more prevalent among carriers of APOE ε4.
Methods: A database of head injured patients was used. Initial assessment was at the time of their injury, between 1968 and 1985, and outcome data at six months were available. Their ages at the time of injury ranged between 2 and 70 years. A cohort of 396 subjects was reassessed at a mean of 18 years later, with determination of APOE genotype and detailed neuropyschological testing.
Results: Judging by the Glasgow outcome scale, twice as many patients had deteriorated as improved between six months after injury and the late assessment; 22.2% of APOE ε4 carriers had a good late outcome compared with 30.5% of non-carriers (95% confidence interval for the difference, -0.7% to 17.2%; p = 0.084). There were no clear differences between ε4 carriers and non-carriers in detailed neuropsychological assessments.
Conclusions: Although this study provides additional evidence that a late decline may occur after head injury, there was no clear relation to APOE genotype. Despite the follow up interval of 15 to 25 years, the cohort is still too young (mean age 42.1 years) to assess the risk of Alzheimer's disease.