APOE-ε4 Is Associated With Reduced Verbal Memory Performance and Higher Emotional, Cognitive, and Everyday Executive Function Symptoms Two Months After Mild Traumatic Brain Injury

More than just risk for Alzheimer's disease: APOE ε4's impact on the aging brain

The apolipoprotein ε4 (APOE ε4) allele is most commonly associated with increased risk for late-onset Alzheimer's disease (AD). However, recent longitudinal studies suggest that these risks are overestimated; most ε4 carriers will not develop dementia in their lifetime. In this article, we review new evidence regarding the impact of APOE ε4 on cognition among healthy older adults. We discuss emerging work from animal models suggesting that ε4 impacts brain structure and function in multiple ways that may lead to age-related cognitive impairment, independent from AD pathology. We discuss the importance of taking an individualized approach in future studies by incorporating biomarkers and neuroimaging methods that may better disentangle the phenotypic influences of APOE ε4 on the aging brain from prodromal AD pathology.

Utilization of clinical and radiological parameters to predict cognitive prognosis in patients with mild-to-moderate traumatic brain injury

Background

Cognitive impairment is a common sequela following traumatic brain injury (TBI). This study aimed to identify risk factors for cognitive impairment after 3 and 12 months of TBI and to create nomograms to predict them.

Methods

A total of 305 mild-to-moderate TBI patients admitted to the First Affiliated Hospital with Nanjing Medical University from January 2018 to January 2022 were retrospectively recruited. Risk factors for cognitive impairment after 3 and 12 months of TBI were identified by univariable and multivariable logistic regression analyses. Based on these factors, we created two nomograms to predict cognitive impairment after 3 and 12 months of TBI, the discrimination and calibration of which were validated by plotting the receiver operating characteristic (ROC) curve and calibration curve, respectively.

Results

Cognitive impairment was detected in 125/305 and 52/305 mild-to-moderate TBI patients after 3 and 12 months of injury, respectively. Age, the Glasgow Coma Scale (GCS) score, >12 years of education, hyperlipidemia, temporal lobe contusion, traumatic subarachnoid hemorrhage (tSAH), very early rehabilitation (VER), and intensive care unit (ICU) admission were independent risk factors for cognitive impairment after 3 months of mild-to-moderate TBI. Meanwhile, age, GCS score, diabetes mellitus, tSAH, and surgical treatment were independent risk factors for cognitive impairment after 12 months of mild-to-moderate TBI. Two nomograms were created based on the risk factors identified using logistic regression analyses. The areas under the curve (AUCs) of the two nomograms to predict cognitive impairment after 3 and 12 months of mild-to-moderate TBI were 0.852 (95% CI [0.810, 0.895]) and 0.817 (95% CI [0.762, 0.873]), respectively.

Conclusion

Two nomograms are created to predict cognitive impairment after 3 and 12 months of TBI. Age, GCS score, >12 years of education, hyperlipidemia, temporal lobe contusion, tSAH, VER, and ICU admission are independent risk factors for cognitive impairment after 3 months of TBI; meanwhile, age, the GCS scores, diabetes mellitus, tSAH, and surgical treatment are independent risk factors of cognitive impairment after 12 months of TBI. Two nomograms, based on both groups of factors, respectively, show strong discriminative abilities.

Interaction between APOE ɛ4 and Age Is Associated with Emotional Distress One Year after Moderate-Severe Traumatic Brain Injury

Emotional distress is common following moderate-severe traumatic brain injury (TBI) and is associated with poorer post-injury outcomes. Previously investigated sociodemographic, psychological, and injury-related factors account for only a small proportion of variance in post-TBI emotional distress, highlighting a need to consider other factors such as genetic factors. The apolipoprotein E gene (APOE) has been commonly studied in the TBI literature, with the ɛ4 allele linked to worse neuronal repair and recovery. Few studies have investigated the potential relationship between APOE ɛ4 and emotional distress after moderate-severe TBI, and results have been varied. We examined whether APOE ɛ4 was associated with emotional distress 1 year following moderate-severe TBI, and whether this relationship was moderated by age, sex, and TBI severity (as indexed by the duration of post-traumatic amnesia [PTA]). Moderate-severe TBI survivors provided saliva samples following inpatient admission to a TBI rehabilitation hospital. They completed a self-report measure of emotional distress, the Hospital Anxiety and Depression Scale (HADS), at a follow-up interview ∼1 year post-injury. Complete genetic and follow-up data were available for 441 moderate-severe TBI survivors (mean age = 39.42 years; 75% male). We constructed a linear regression model that included APOE ɛ4 carriage status (carrier vs. non-carrier) and interactions with age, sex, and TBI severity (APOE × age, APOE × sex, APOE × age × sex, and APOE × PTA duration) to predict total score on the HADS, while covarying for the main effects of age, sex, PTA duration, and previous head injury. There was a significant main effect of APOE ɛ4, whereby ɛ4 carriers reported less emotional distress than non-carriers (p = 0.04). However, we also found a significant interaction with age such that APOE ɛ4 carriers reported increasingly greater emotional distress with older age compared with non-carriers (p = 0.01). A sensitivity analysis (n = 306) suggested that the APOE × age interaction, and main effects of age and previous head injury, were not unique to individuals with pre-injury mental health problems (n = 136). However, the main effect of APOE ɛ4 was no longer significant when individuals with pre-injury mental health problems were removed. Our findings highlight the importance of considering moderation of genetic associations, suggesting that APOE ɛ4 may be a risk factor for emotional distress specifically among older survivors of moderate-severe TBI. If these findings can be independently replicated, APOE ɛ4 carriage status, interpreted in the context of age, could be incorporated into risk prediction models of emotional distress after moderate-severe TBI, enhancing targeted early detection and intervention efforts.