Substantial effects of apolipoprotein E ε4 on memory decline in very old age: longitudinal findings from a population-based sample

APOE-ε4 is not associated with pure-tone hearing thresholds, visual acuity or cognition, cross-sectionally or over 3 years of follow up in the Canadian Longitudinal Study on Aging

INTRODUCTION

Hearing loss and diminished visual acuity are associated with poorer cognition, but the underlying mechanisms are not understood. The apolipoprotein (APOE) ε4 allelic variant may drive the associations. We tested whether APOE-ε4 allele count (0, 1, or 2) was associated with declines in memory, executive function, pure-tone hearing threshold averages, and pinhole-corrected visual acuity among participants in the Canadian Longitudinal Study on Aging (CLSA).

METHODS

Multivariable linear mixed regression models were utilized to assess associations between APOE-ε4 allele count and each of the outcome variables. For each main effects model, interactions between APOE-ε4 and sex and age group (45-54-, 55-64-, 65-74-, and 75-85 years) respectively, were analyzed.

RESULTS

Significant associations were not observed in main effects models. Models including APOE-ε4 * age (but not APOE-ε4 * sex) interaction terms better fit the data compared to main effects models. In age group-stratified models, however, there were minimal differences in effect estimates according to allele count.

CONCLUSION

APOE-ε4 allele count does not appear to be a common cause of sensory-cognitive associations in this large cohort.

Diabetes and cognitive decline

Epidemiologic studies have documented an association between diabetes and increased risk of cognitive decline in the elderly. Based on animal model studies, several mechanisms have been proposed to explain such an association, including central insulin signaling, neurodegeneration, brain amyloidosis, and neuroinflammation. Nevertheless, the exact mechanisms in humans remain poorly defined. It is reasonable, however, that many pathways may be involved in these patients leading to cognitive impairment. A major aim of clinicians is identifying early onset of neurologic signs and symptoms in elderly diabetics to improve quality of life of those with cognitive impairment and reduce costs associated with long-term complications. Several biomarkers have been proposed to identify diabetics at higher risk of developing dementia and diagnose early stage dementia. Although biomarkers of brain amyloidosis, neurodegeneration and synaptic plasticity are commonly used to diagnose dementia, especially Alzheimer disease, their role in diabetes remains unclear. The aim of this review is to explore the molecular mechanisms linking diabetes with cognitive decline and present the most important findings on the clinical use of biomarkers for diagnosing and predicting early cognitive decline in diabetics.

Cognitive dispersion and ApoEe4 genotype predict dementia diagnosis in 8-year follow-up of the oldest-old

BACKGROUND

Cognitive dispersion, or inconsistencies in performance across cognitive domains, has been posited as a cost-effective tool to predict conversion to dementia in older adults. However, there is a dearth of studies exploring cognitive dispersion in the oldest-old (>80 years) and its relationship to dementia incidence.

OBJECTIVE

The main aim of this study was to examine whether higher cognitive dispersion at baseline was associated with dementia incidence within an 8-year follow-up of very old adults, while controlling for established risk factors and suggested protective factors for dementia.

METHODS

Participants (n = 468) were from the Origins of Variance in the Old-Old: Octogenarian Twins study, based on the Swedish Twin Registry. Cox regression analyses were performed to assess the association between baseline cognitive dispersion scores and dementia incidence, while controlling for sociodemographic variables, ApoEe4 carrier status, co-morbidities, zygosity and lifestyle engagement scores. An additional model included a composite of average cognitive performance.

RESULTS

Cognitive dispersion and ApoEe4 were significantly associated with dementia diagnosis. These variables remained statistically significant when global cognitive performance was entered into the model. Likelihood ratio tests revealed that cognitive dispersion and cognitive composite scores entered together in the same model was superior to either predictor alone in the full model.

CONCLUSIONS

The study underscores the usefulness of cognitive dispersion metrics for dementia prediction in the oldest-old and highlights the influence of ApoEe4 on cognition in very late age. Our findings concur with others suggesting that health and lifestyle factors pose little impact upon cognition in very advanced age.

APOE-ε4 Genotype and Dementia Before and After Transient Ischemic Attack and Stroke: Population-Based Cohort Study

Background and Purpose- APOE-ε4 genotype is a risk factor for sporadic Alzheimer disease and reduced recovery from brain injury. Since data on APOE genotype and dementia associated with transient ischemic attack/stroke are sparse, we determined the associations in a longitudinal population-based cohort. Methods- All patients with transient ischemic attack or stroke (2002-2012) in a defined population of 92 728 OxVASC (Oxford Vascular Study) had follow-up to 5-years. Pre-event and incident postevent dementia were ascertained through direct patient assessment and follow-up, supplemented by review of hospital/primary care records. Associations between pre- and post-event dementia and APOE genotype (ε4/ε4-homozygous and ε4/ε3-heterozygous versus ε3/ε3) were examined using logistic regression and Cox regression models, respectively, adjusted for age, sex, education, cerebrovascular burden (stroke severity, prior stroke, white matter disease), diabetes mellitus, and dysphasia. Results- Among 1767 genotyped patients (mean/SD age, 73.0/13.0 years, 901 [51%] male, 602 [34%] transient ischemic attack), 1058 (59.9%) were APOE-ε3/ε3, 403 (22.8%) were ε4/ε3 and 30 (1.7%) were ε4-homozygous. Homozygosity was associated with both pre-event (adjusted odds ratio, 5.81 [95% CI, 1.93-17.48]; P=0.002) and postevent dementia (adjusted hazard ratio, 3.64 [95% CI, 1.90-7.00]; P<0.0001). Association with postevent dementia was maintained after further adjustment for baseline cognitive impairment (hazard ratio, 2.41 [95% CI, 1.19-4.89]; P=0.01). There were no associations overall between ε4/ε3 and pre-event dementia (adjusted odds ratio, 1.47 [95% CI, 0.88-2.45]; P=0.14) or postevent dementia (hazard ratio, 1.11 [95% CI, 0.84-1.48]; P=0.47). Conclusions- In patients with transient ischemic attack and stroke, APOE-ε4 homozygosity was associated with both pre- and post-event dementia. Associations were independent of cerebrovascular burden and may be mediated through increased neurodegenerative pathology or vulnerability to injury.

Apolipoprotein E ε4 allele effects on longitudinal cognitive trajectories are sex and age dependent

INTRODUCTION

Questions remain about whether apolipoprotein E (APOE)-ε4 effects on cognitive decline are similar in men and women and how APOE-ε4 and age interact to influence decline in different cognitive domains.

METHODS

In sex-stratified analyses, baseline age-dependent associations between APOE-ε4 status and longitudinal cognitive trajectories were examined in cognitively normal Caucasian older adults (631 men, 561 women, baseline age range: 50-93, 6733 assessments).

RESULTS

In men, older baseline age was associated with greater effects of APOE-ε4 on longitudinal decline in memory and executive function, detectible from baseline age of 64 and 68, respectively. In women, older baseline age was associated with greater APOE-ε4 effects on longitudinal decline in attention, detectible at baseline age of 66. No significant APOE-ε4 effects were found for language, visual-spatial ability, or processing speed.

DISCUSSION

Results highlight the importance of considering sex and age when assessing APOE-ε4-associated vulnerability to cognitive decline.

Effects of APOE on cognitive aging in community-dwelling older adults

OBJECTIVE

The apolipoprotein E (APOE) gene is an established risk factor for sporadic Alzheimer's disease, with elevated risk for ε4-carriers and reduced risk for ε2-carriers. However, it is unclear whether APOE modifies risk for cognitive decline in normal aging. The objective of this study was to determine whether ε2 and ε4 are associated with rates of normal cognitive aging, and whether associations of ε4 with cognitive decline are modified by sex, education or health behaviors (exercise, alcohol consumption, smoking).

METHOD

A community-based sample of 1,393 older adults were genotyped for APOE and underwent cognitive assessment up to seven times over a maximum of period of 27 years.

RESULTS

ε2-carriers showed slower executive function decline with age relative to ε3 homozygotes or ε4-carriers, whereas ε4-carriers demonstrated more rapid executive function and verbal fluency decline. Accelerated executive function decline was particularly pronounced in ε4-carriers with lower education. After excluding individuals with cognitive impairment, faster executive function decline was still apparent in ε4-carriers, and the effect of ε4 on episodic memory interacted with alcohol consumption, such that only ε4-carriers who did not drink showed more rapid memory decline than ε4 noncarriers. The influence of ε4 on cognitive aging did not differ by sex, nor was it modified by smoking or exercise.

CONCLUSIONS

These findings indicate that the ε2 and ε4 alleles have differential effects on cognitive aging, and that negative effects of ε4 may be partly mitigated by behavioral choices. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Effect of Aluminum-Maltolate on the Content of Aβ Protein and the Expression of ApoER2, VLDLRs, and LRP1 in PC12-ApoE4 Cells

To investigate the effect of aluminum-maltolate [Al(mal)3] on the expression of ApoER2, VLDLRs, and LRP1 in PC12-ApoE4 cells. The lentiviral vector carrying human ApoE4 gene was transfected into PC12 cells; after screening with puromycin, PC12 cells carrying ApoE4 gene (PC12-ApoE4 cells) were established. After 24-h treatment with Al(mal)3, the cell survival rate was measured by CCK-8 assay. The expression of Aβ40 and Aβ42 was detected by ELISA assay; the expression of the APP, ApoER2, LRP1, and VLDLRs genes was detected by RT-PCR, and Western blot assay was used to detect the expression of the APP, ApoER2, LRP1, and VLDLRs proteins. Factorial experiment design was performed to analyze interaction between cell type and Al dose. Al(mal)3 treatment induced dose-dependent decreases of survival rate in the two cell groups and dose-dependent increases of Aβ42 content(P < 0.05). The expressions of ApoER2, LRP1, and VLDLR proteins and their mRNA transcription decreased gradually with the increase of Al(mal)3 doses (P < 0.05), while the expression of APP protein and mRNA transcription gradually increased with the increase of Al(mal)3 doses (P < 0.05). As regard to the interaction of cell type and Al dose, the decrease of cell survival rate and the increase of the Aβ42 were both statistically significant (P < 0.05). And the decrease of ApoER2 and LRP1 proteins was both statistically significant too (P < 0.05). The effect of Al(mal)3 and ApoE4 gene on the survival rate and the increase of Aβ content in PC12 cells. That is to say, there is interaction between ApoE4 gene and aluminum on the Aβ content, especially the change of the Aβ42 content, which may be related to the down-regulation of the expression of ApoER2 and LRP1 proteins.

Does incipient dementia explain normal cognitive decline determinants? Lothian birth cohort 1921

The presence of an apolipoprotein E (APOE) ε4 allele, lower physical fitness, smoking, and lower serum vitamin B-12 have been reported as contributing to poorer cognitive function in LBC1921 at age 79, after adjusting for childhood intelligence. Because incident dementia was not previously ascertained within LBC1921, it is possible that preclinical or unrecognized cases at age 79 influenced findings. Dementia cases arising over approximately 16 years of follow-up were determined by a consensus using evidence from electronic medical records, death certificates, and clinical reviews. The analyses from the original reports were repeated after the exclusion of those who had developed dementia. In a subsequent set of analyses, the authors considered the potential impact of terminal decline, excluding those participants who died within 4 years of baseline testing. Positive APOE ε4 status was found to be associated with poorer Logical Memory (Wechsler, 1987) at age 79 (F(1, 355) = 8.16, p = .005, ηp2 = 0.022; n = 359) and lower Moray House Test (Scottish Council for Research in Education, 1933) score at age 79 (F(1, 357) = 4.27, p = .04, ηp2 = 0.012; n = 363). Lower age 79 IQ was associated with smoking (F(2, 360) = 3.67, p = .026, ηp2 = 0.020; n = 367), lower vitamin B-12 (Sβ = 0.11, p = .014; n = 367), and poorer physical fitness (Sβ = 0.21, p < .001; n = 359). Only the relationship with physical fitness remained significant after excluding those who died within 4 years of baseline (Sβ = 0.203, p < .001; n = 310). Unrecognized dementia had little or no effect on determinants of lifetime cognitive ageing in LBC1921. Terminal decline may have accounted for the associations with age 11 to age 79 cognitive change. (PsycINFO Database Record

APOE ε4 Modulation of Training Outcomes in Several Cognitive Domains in a Sample of Cognitively Intact Older Adults

BACKGROUND

Most research points to the ɛ4 allele of the apolipoprotein E (APOE) gene as the most recognizable genetic risk factor associated with Alzheimer's disease pathogenesis. It has been also suggested that the APOEɛ4 allele has a negative influence on cognitive functioning, which begins long before cognitive impairment becomes manifest. However, still, little is known about the APOEɛ4 interaction with cognitive intervention programs.

OBJECTIVE

The main goal of this study was to explore whether there was a differential APOE genotype modulation effect after cognitive training in different domains, such as language comprehension, executive functions, and memory. Contrary to other studies, hippocampal volume was controlled for.

METHODS

Fifty older adults (65+ years; 30 women and 20 men) participated in a multi-domain cognitive training that involved 30 sessions taking place over 12 weeks. Half of the participants were APOEɛ4 carriers. The control group was matched in age, gender, normalized hippocampal volume, cognitive reserve, Mini-Mental State Examination score, and Geriatric Depression Scale-Short Version.

RESULTS

The study revealed that there were consistent treatment benefits in complex sentence comprehension (noncanonical sentences and sentences with two propositions), a domain that was not directly trained, but only in the A POEɛ4 noncarrier group.

CONCLUSION

Genetic profile modulates training outcomes in sentence comprehension.

Changes in Frailty Predict Changes in Cognition in Older Men: The Honolulu-Asia Aging Study

BACKGROUND

As cognitive decline mostly occurs in late life, where typically it co-exists with many other ailments, it is important to consider frailty in understanding cognitive change.

OBJECTIVE

Here, we examined the association of change in frailty status with cognitive trajectories in a well-studied cohort of older Japanese-American men.

METHODS

Using the prospective Honolulu-Asia Aging Study (HAAS), 2,817 men of Japanese descent were followed (aged 71-93 at baseline). Starting in 1991 with follow-up health assessments every two to three years, cognition was measured using the Cognitive Abilities Screening Instrument (CASI). For this study, health data was used to construct an accumulation of deficits frailty index (FI). Using six waves of data, multilevel growth curve analyses were constructed to examine simultaneous changes in cognition in relation to changes in FI, controlling for baseline frailty, age, education, and APOE-ɛ4 status.

RESULTS

On average, CASI scores declined by 2.0 points per year (95% confidence interval 1.9-2.1). Across six waves, each 10% within-person increase in frailty from baseline was associated with a 5.0 point reduction in CASI scores (95% confidence interval 4.7-5.2). Baseline frailty and age were associated both with lower initial CASI scores and with greater decline across the five follow-up assessments (p < 0.01).

DISCUSSION

Cognition is adversely affected by impaired health status in old age. Using a multidimensional measure of frailty, both baseline status and within-person changes in frailty were predictive of cognitive trajectories.

Apolipoprotein E (APOE) ε4 and episodic memory decline in Alzheimer's disease: A review

A growing body of research has examined the relationship between episodic memory decline, the cognitive hallmark of Alzheimer's disease (AD), and the presence of Apolipoprotein E ε4 (APOE ε4) allele, a major genetic risk factor for the disease. Our review attempts to summarize and critically evaluate this literature. We performed a systematic search for studies assessing episodic memory in AD patients who were genotyped for APOE ε4 and identified fourteen papers. Although most of these papers reported significant relationships between APOE ε4 and episodic memory decline in AD, some papers did not confirm this relationship. Our review links this controversy to the conflicting literature about the effects of APOE ε4 on general cognitive functioning in AD. We identify several shortcoming and limitations of the research on the relationship between APOE ε4 and episodic memory in AD, such as small sample sizes, non-representative populations, lack of comparison of early-onset vs. late-onset disease, and lack of comparison among different genotypes that include APOE ε4 (i.e., zero, one, or two ε4 alleles). Another major shortcoming of the reviewed literature was the lack of comprehensive evaluation of episodic memory decline, since episodic memory was solely evaluated with regard to encoding and retrieval, omitting evaluation of core episodic features that decline in AD, such as context recall (e.g., how, where, and when an episodic event has occurred) and subjective experience of remembering (e.g., reliving, emotion and feeling during episodic recollection). Future research taking these limitations into consideration could illuminate the nature of the relationship between APOE ε4 and episodic memory decline in AD.

APOE ε4 allele is associated with worse performance in memory dimensions of the mini-mental state examination: the Bambuí Cohort Study of Aging

OBJECTIVE

This study aimed to investigate the correlation between apolipoprotein E (APOE) ε4 and the mini-mental state examination (MMSE) dimension in an elderly population, using baseline data from the Bambui (Brazil) Cohort Study of Aging.

DESIGN

We conducted a community-based cross-sectional study.

SETTING

The study took place at Bambui city, Minas Gerais State, Southeast Brazil.

PARTICIPANTS

A total of 1408 (87.7%) cohort participants had complete information on the MMSE and health measures.

MEASUREMENTS

The association between each of five dimensions (concentration, language/praxis, orientation, attention, and memory) underlying the MMSE and APOE ε4 allele was assessed using multivariate linear regression models. Potential confounding variables included sociodemographic factors and selected biomarkers.

RESULTS

The main finding is a strong negative association between the presence of APOE ε4 allele and memory dimension in the MMSE (fully adjusted β coefficient = -0.14; 95% confidence interval: -0.27 to -0.04; p = 0.016). No other cognitive dimensions showed significant associations with the APOE ε4 allele.

CONCLUSION

This study is the first to investigate the association between dimensions of the MMSE, obtained from principal component analysis and APOE ε4 carrier status in community-dwelling older adults taking into account a range of potential confounding factors. We found a strong negative association between the presence of APOE ε4 allele and scores on memory dimension of the MMSE, but no effect on other dimensions. Our results reinforce previous data on the literature that APOE ε4 allele has a significant effect on cognitive performance that can be detected even in screening tests, such as the MMSE.

The ApoE4 genotype modifies the relationship of long-term glycemic control with cognitive functioning in elderly with type 2 diabetes

AIM

To assess whether the APOE4 genotype affects the relationship of long-term glycemic control with cognitive function in elderly with type 2 diabetes (T2D).

METHODS

Participants were cognitively normal and pertained to a Diabetes Registry which provided access to HbA1c levels and other T2D related factors since 1998. Glycemic control was defined as the mean of all HbA1c measurements available (averaging 18 measurements) per subject. Four cognitive domains (episodic memory, semantic categorization, attention/working memory and executive function), based on factor analysis and an overall cognitive score (the sum of the 4 cognitive domains) were the outcome measures.

RESULTS

The analysis included 808 subjects; 107 (11.9%) subjects had ≥1ApoE4 allele. In ApoE4 carriers, higher mean HbA1c level was significantly associated with lower scores on all cognitive measures except attention/working memory (p-values ranging from 0.047 to 0.003). In ApoE4 non-carriers, higher mean HbA1c level was significantly associated with lower scores on executive function, but not with other cognitive measures-despite the larger sample size. Compared to non-carriers, there were significantly stronger associations in ApoE4 carriers for overall cognition (p=0.02), semantic categorization (p=0.03) and episodic memory (p=0.02), and the difference for executive function approached statistical significance (p=0.06).

CONCLUSION

In this cross-sectional study of cognitively normal T2D subjects, higher mean HbA1c levels were generally associated with lower cognitive performance in ApoE4 carriers, but not in non-carriers, suggesting that ApoE4 affects the relationship between long-term glycemic control and cognition, so APOE4 carriers may be more vulnerable to the insults of poor glycemic control.