Role of Apolipoprotein E Gene Variants in Cognitive Outcome of Patients after Moderate Degree Diffuse Brain Injuries

Introduction: Diffuse Brain Injury (DBI) has been shown to be the major form of the primary brain traumatic injury. Apolipoprotein E (APOE) is considered to be associated in the prognosis of DBI. Aim: To analyse change in cognitive outcome of moderate degree DBI patients and its association with APOE gene polymorphism. Materials and Methods: This prospective cohort study was conducted at the Department of Genetics and Molecular Medicine, Kamineni Hospitals, LB Nagar, Hyderabad, Telangana, India, from March 2018 to May 2019, in which 23 patients who had moderate DBI were included. Patients were genotyped for APOE polymorphism and intellectual function was assessed when the patient was being discharged using Mini Mental State Examination (MMSE) score and was repeated after three months. Wilcoxon Signed Rank Test was used to determine the change in MMSE score taken at the time of discharge and after three months in follow-up. Results: Of the total 23 patients, 19 (82.60) were males and 4 (17.40%) were females where the average age of subjects included was 41.59±17.64 years. E2/E3 APOE genotype was present in 16 (69.56%) subjects. The improvement of MMSE score at the end of three months following discharge showed that best recovery was in subjects with E2/E3, genotype with mean of 4.9±2.1, followed by E2/E2 i.e., 3.5±2.6. In order to evaluate the changes in MMSE score at the time of discharge and after three months due to the presence of APOE genotype E2/E3 a Wilcoxon Signed Rank Test was performed which revealed statistically significant positive change in MMSE score after three months, z=-3.512, p=0.00044, with a large effect size (r=0.620). Conclusion: This preliminary study indicated that APOE E2/ E3 individuals showed a better recovery after traumatic brain injuries based on MMSE scores. However, extended studies are needed to establish this which may also give more weightage for genotyping APOE as a prognostic marker.