APOE and Cognitive impairment: The APOE ε4 allele is a well-established risk factor for cognitive impairment progression and Alzheimer disease51; however, after TBI, it is also implicated in slower recovery,52 greater cognitive impairment in memory and attention,53 and greater inflammatory response.54 The results adjusting for APOE ε4 still showed TBI and seizures as being associated with a risk of progression to cognitive impairment.