Frequency of the apolipoprotein E ε4 allele in a memory clinic cohort in Beijing: a naturalistic descriptive study

Protective effect of apolipoprotein E epsilon 3 on sporadic Alzheimer's disease in the Chinese population: a meta-analysis

Alzheimer's disease (AD) is fast becoming one of the most expensive, deadly and burdensome diseases in this century. It has the fastest-growing disease burden in China. Apolipoprotein E (APOE) polymorphic alleles are generally considered to be the primary genetic determinant of AD risk: individuals with the E4 allele are at increased risk of AD compared with individuals with the more common E3 allele. Since the intensity of the association varies among different ethnic groups, a separate meta-analysis of the Chinese population is needed. We searched Chinese and English databases to sift through literature over the past 20 years. Data on the APOE genotype and AD were collected for correlation analysis. OR was calculated according to APOE allele and genotype. A publication bias analysis and sensitivity analysis were performed, and the main results were further verified by subgroup analysis. The 116 eligible studies enrolled 23,396 patients with AD and 25,568 healthy controls. The study subjects covered at least 30 of the 34 provincial-level administrative regions (including Taiwan). The partial sex ratio was as follows: AD male/female; 10,291/11,240; control male/female, 11,304/12,428, [Formula: see text] = 0.122, P = 0.727. The results of the meta-analysis of alleles showed that I² > 50% and Q statistics were significant for all genotypes; therefore, the random effect model was selected. The frequency of the ApoE ε4 allele in AD was higher than that in healthy controls, and the difference was statistically significant (OR 2.847, 95% CI [2.611-3.101], P < 0.001). The frequencies of ApoE ε3 and ε2 in AD were lower than those in healthy controls, and the differences were statistically significant (ε3: OR 0.539, 95% CI [0.504-0.576], P < 0.001; ε2: OR 0.771, 95% CI [0.705-0.843], P < 0.001). The results of the meta-analysis of AD genotype showed that ApoE ε2/ε4 (OR 1.521, 95% CI [1.270-1.823], P < 0.001), ε3/ε4 (OR 2.491, 95% CI [2.267-2.738], P < 0.001) and ε4/ε4 (OR 5.481, 95% CI [4.801-6.257], P < 0.001) allele genotype frequencies were higher than those of the healthy controls. The differences were all statistically significant. Moreover, the ApoE ε2/ε2 (OR 0.612, 95% CI [0.504-0.743], P < 0.001), ε2/ε3 (OR 0.649, 95% CI [0.585-0.714], P < 0.001) and ε3/ε3 (OR 0.508, 95% CI [0.468-0.551], P < 0.001) genotypes were less frequent in patients with AD than in healthy controls, and the differences were statistically significant. The results of the sensitivity analysis and subgroup analysis were consistent with those of the whole model. These results provide support for the protective effect of the ApoE ε3/ε3 genotype against the development of AD. This research is the most comprehensive meta-analysis of the correlation between APOE and AD in the Chinese population by analysing the distribution of the APOE gene in patients with AD reported in the last 20 years. It was concluded that the APOE ε3 allele had a protective effect against sporadic AD in the Chinese population, with great significance, and that its protective effect was stronger than that of the ε2 allele.

APOE ε4 Allele Distribution and Association With Scores of Subjective Cognitive Decline Questionnaire 9 in a Large Chinese Memory Clinic Cohort

Background

Previous reports on APOE ε4 allele distribution in different populations have been inconclusive. The Subjective Cognitive Decline-Questionnaire 9 (SCD-Q9) was developed to identify those at risk of objective cognitive impairment [OCI; including mild cognitive impairment (MCI) and dementia groups), but its association with APOE ε4 and discriminatory powers for SCD_{with subtle cognitive decline} (SCDs) and OCI in memory clinics are unclear.

Objectives

To investigate demographic distribution of APOE ε4, its association with SCD-Q9 scores, and its ability to discriminate SCDs and OCI groups from normal control (NC).

Methods

A total of 632 participants were recruited (NC = 243, SCDs = 298, OCI = 91). APOE ε4 allele distribution and association with SCD-Q9 scores were calculated and the effects on cognitive impairment were analyzed. Receiver operating characteristic (ROC) analysis was applied to identify discriminatory powers for NC, SCDs, and OCI.

Results

Total APOE ε4 frequency was 13.1%. This did not vary by demography but was higher in patients with OCI. The SCD-Q9 scores were higher in APOE ε4 carriers than non-carriers in the OCI group. The area under the curve (AUC) for discriminating from OCI using APOE ε4 were 0.587 and 0.575, using SCD-Q9 scores were 0.738 and 0.571 for NC and SCDs groups, respectively. When we combined APOE ε4 and SCD-Q9 scores into the model, the AUC increased to 0.747 for discriminating OCI from NC. However, when OCI group was split into MCI and dementia groups, only total SCD-Q9 score was the independent affecting factor of MCI.

Conclusion

This study demonstrated that the distribution of APOE ε4 alleles did not vary with different demographic characteristics in a large-scale cohort from a memory clinic. APOE ε4 alleles may be associated with scores of SCD-Q9 reflecting the degree of cognitive complaints but their additional contribution to SCD-Q9 scores is marginal in discriminating between NC, SCDs, and OCI.

Impact of Shift Work and Long Working Hours on Worker Cognitive Functions: Current Evidence and Future Research Needs

Particular working conditions and/or organization of working time may cause important sleep disturbances that have been proposed to be predictive of cognitive decline. In this regard, circadian rhythm misalignment induced by exposure to night work or long working hours would be responsible for cognitive impairment. Nevertheless, evidence supporting this correlation is limited and several issues still need to be elucidated. In this regard, we conducted a systematic review to evaluate the association between shift/night work and cognitive impairment and address its main determinants. Information provided by the reviewed studies suggested that night work might have serious immediate negative effects especially on cognitive domains related to attention, memory and response inhibition. Furthermore, cognitive performance would progressively worsen over consecutive night shifts or following exposure to very long work shifts. Otherwise, conflicting results emerged regarding the possible etiological role that night work chronic exposure would have on cognitive impairment. Therefore, circadian rhythm desynchronization, lack of sleep and fatigue resulting from night work may negatively impact worker’s cognitive efficiency. However, in light of the considerable methodological variability of the reviewed studies, we proposed to develop a standardized research and evaluation strategy in order to obtain a better and comprehensive understanding of this topic.

Apolipoprotein E Gene Revisited: Contribution of Rare Variants to Alzheimer's Disease Susceptibility in Southern Chinese

BACKGROUND

APOE ε4 is the best-known risk factor for late-onset alzheimer's disease (AD). Population studies have demonstrated a relatively low prevalence of APOE ε4 among Chinese population, implying additional risk factors that are Chinese-specific may exist. Apart from - alleles, genetic variation profile along the full-length APOE has rarely been investigated.

OBJECTIVE

In this study, we filled this gap by comprehensively determining all genetic variations in APOE and investigated their potential associations with late-onset AD and mild cognitive impairment (MCI) in southern Chinese.

METHODS

Two hundred and fifty-seven southern Chinese participants were recruited, of whom 69 were AD patients, 83 had MCI, and 105 were normal controls. Full-length APOE from promoter to 3'UTR regions were sequenced. Genetic variants were identified and compared among the three groups.

RESULTS

While APOE ε4 was more significantly found in AD patients, the prevalence of APOE ε4 in southern Chinese AD patients was the lowest when compared to other areas of China and nearby regions, as well as other countries worldwide. We further identified 13 rare non-singleton variants in APOE. Significantly more AD patients carried any of the rare non-singleton variants than MCI and normal subjects. Such difference was observed in the non-carriers of ε4-allele only. Among the identified rare variants, the potential functional impact was predicted for rs532314089, rs553874843, rs533904656 and rs370594287.

CONCLUSION

Our study suggests an ethnic difference in genetic risk composition of AD in southern Chinese. Rare variants on APOE are a potential candidate for AD risk stratification biomarker in addition to APOE-ε4.

Distribution and clinical impact of apolipoprotein E4 in subjective memory impairment and early mild cognitive impairment

The apolipoprotein E (APOE) e4 allele is the most common genetic variant associated with Alzheimer’s disease (AD). We sought to investigate the distribution of APOE genotypes across the full clinical AD spectrum including AD, late-stage amnestic mild cognitive impairment (L-aMCI), early-stage aMCI (E-aMCI), subjective memory impairment (SMI), and controls. We prospectively recruited 713 AD patients, 735 aMCI patients, 575 SMI patients, and 8,260 individuals as controls. The frequency of the APOE e4 allele revealed an ordered fashion in the AD (30.8%), L-aMCI (24.0%), E-aMCI (15.1%), SMI (11.7%), and control (9.1%) groups. APOE e3/e4 and e4/e4 genotype frequencies also appeared in an ordered fashion in the AD group (39.1% of e3/e4 and 10.9% of e4/e4), as well as the L-aMCI (28.3% and 9.4%), E-aMCI (22.3% and 3.7%), SMI (18.3% and 1.9%), and control (15.1% and 0.8%) groups. In the comparisons of APOE e3/e3 vs. e3/e4 genotypes, all patient groups had a higher frequency of APOE e3/e4 relative to the control group. Relative to the SMI and E-aMCI groups, the AD and L-aMCI groups had higher frequency of the APOE e3/e4 genotype, and the AD group had a higher frequency relative to the L-aMCI group. However, there was no significant difference between the E-aMCI and SMI groups. In our longitudinal data, APOE e4 carrier showed a steeper incline slope in a clinical dementia rating sum of boxes (CDR-SB) score than APOE e4 non-carrier in SMI (B = 0.0066, p = 0.0104), E-aMCI (B = 0.0313, p < 0.0001), and L-aMCI (B = 0.0178, p = 0.0007). APOE e4 carrier showed a steeper decline slope in the CDR-SB than APOE e4 non-carrier in AD (B = − 0.0309, p = 0.0003). These findings suggest that E-aMCI and SMI are associated with a similarly increased frequency of the APOE e4 allele compared to controls, suggesting a greater genetic risk for AD and the importance of monitoring the allele more closely.

Decision-Making Under Ambiguity or Risk in Individuals With Alzheimer's Disease and Mild Cognitive Impairment

BACKGROUND

Making advantageous decisions is essential in everyday life. Our objective was to assess how patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD) make decisions under conditions of ambiguity or risk. In addition, the study also aimed to examine the relationship between decision-making competence and memory and executive function.

METHODS

Patients with MCI (n = 36) and AD (n = 29) and healthy elderly controls (HC, n = 34) were recruited from the memory clinic. All subjects were administered a comprehensive neuropsychological battery test. We used the Iowa Gambling Task (IGT) to measure decision-making under ambiguity and the Game of Dice Task (GDT) to measure decision-making under risk. Pearson's correlation was used to examine the relationship between the performance of IGT and GDT with delayed recall and the Stroop test.

RESULTS

In the GDT, MCI and AD patients presented similar performance but showed different patterns when compared with the HC group. The proportion of those making advantageous choices was lower in the AD group than in the HC group (p = 0.01), while the MCI and HC groups did not differ (p = 0.14). Meanwhile, concerning the ratio of accepting negative feedback, the AD (p < 0.01) group was significantly different from the HC patients, but the MCI (p = 0.06) and HC groups did not differ. In the IGT, MCI and AD patients selected randomly from advantageous and disadvantageous decks (p = 0.94 and p = 0.54), showing no significant change in performance over time. In contrast, the HC group made increasingly frequent advantageous selections over time (p = 0.04). Furthermore, the proportion of advantageous decision-makers for the GDT had a linear relationship with delayed recall of the Hopkins Verbal Learning Test and Stroop color words (p < 0.01 and p < 0.01, respectively).

CONCLUSION

Our findings suggest that decision-making ability under ambiguity is compromised in MCI and AD, and the decision-making under risk is only impaired in AD. Reduced decision-making performance under risk is closely correlated with lower executive functions and memory.

Cognitive test battery for evaluating elderly Chinese Americans

ABSTRACTObjectives:This study aimed to determine the diagnostic utility of a Chinese test battery for evaluating cognitive loss in elderly Chinese Americans.

METHODS

Data from a pilot study at the Mount Sinai Alzheimer's Disease Research Center was examined. All participants were &gt; 65 years old, primarily Chinese speaking, with adequate sensorimotor capacity to complete cognitive tests. A research diagnosis of normal mild cognitive impairment (MCI) or Alzheimer's disease (AD) was assigned to each participant in consensus conference. Composite scores were created to summarize test performance on overall cognition, memory, attention executive function, and language. Multivariable logistic regression models were used to assess the sensitivity of each cognitive domain for discriminating three diagnostic categories. Adjustment was made for demographic variables (i. e., age, gender, education, primary language, and years living in the USA).

RESULTS

The sample included 67 normal, 37 MCI, and 12 AD participants. Performance in overall cognition, memory, and attention executive function was significantly worse in AD than in MCI, and performance in MCI was worse than in normal controls. Language performance followed a similar pattern, but differences did not achieve statistical significance among the three diagnostic groups.

CONCLUSIONS

This study highlights the need for cognitive assessment in elderly Chinese immigrants.

Cortical Thickness and Microstructural White Matter Changes Detect Amnestic Mild Cognitive Impairment

Both the apolipoprotein E (APOE) ɛ4 allele and amnestic mild cognitive impairment (aMCI) are considered to be risk factors for Alzheimer's disease (AD). The primary aim of this study was to determine whether the aMCI-related abnormality in gray matter (GM) cortical thickness and white matter (WM) tracts integrity would be modified by the APOE genotype. A total of 146 older adults, including 64 aMCI patients (28 ɛ4 carriers and 36 non-carriers) and 82 healthy controls (39 ɛ4 carriers and 43 non-carriers), underwent a standardized clinical interview, neuropsychological battery assessment, and multi-modal brain magnetic resonance imaging scans. Compared with control subjects, the patients with aMCI showed significantly reduced cortical thickness bilaterally in the parahippocampal gyrus and disrupted WM integrity in the limbic tracts (e.g., increased mean diffusivity in the right parahippocampal cingulum and bilateral uncinate fasciculus). However, no significant main effects of the APOE genotype and diagnosis-by-genotype interaction on GM thickness and WM integrity were observed. Further, diffusivity measures of the limbic WM tracts were significantly correlated with the parahippocampal atrophy in aMCI. Importantly, the parahippocampal thickness and diffusivity measures of the limbic WM tracts were significantly correlated with the cognitive performance (i.e., episodic memory Z score) in patients with aMCI. These results demonstrate that WM microstructural disruptions in the limbic tracts are present at the early stage of AD in an APOE-independent manner; and this degeneration may occur progressively, in parallel with parahippocampal atrophy, and may specifically contribute to early initial impairment in episodic memory.

Apolipoprotein E e4 Allele Is Associated with Subjective Cognitive Decline: A Meta-Analysis

BACKGROUND AND PURPOSE

Subjective cognitive decline (SCD) is a condition associated with increased risk of Alzheimer's disease. This study performs a meta-analysis to estimate the prevalence of the Apolipoprotein E e4 (APOE e4) allele in SCD and the association of APOE e4 with SCD.

METHODS

The MEDLINE, EMBASE, and Cochrane Library databases were searched. Meta-analyses were conducted using STATA 12.0 software. When significant heterogeneity was present (I2 >50% and p < 0.05), we conducted stratified and meta-regression analyses to explore possible reasons for heterogeneity.

RESULTS

We selected a total of 28 studies that were conducted in Australia, the United States, northern Europe, middle Europe, southern Europe, and Asia. The sample size of the SCD group was 6,044. Thirteen studies included a healthy control group (total control cohort of 3,822), whereas the remaining 15 studies were single-arm studies of SCD groups. The APOE e4 allele was associated with SCD (OR 1.12 [1.00-1.25]; p = 0.04). The pooled estimate for APOE e4 carrier prevalence was 32% (95% CI 28-35). Due to the significant heterogeneity in prevalence estimates, we performed stratified and meta-regression analyses and found that age and northern European residency were significantly associated with heterogeneity.

CONCLUSION

The results of this meta-analysis indicate a weak association between APOE e4 and SCD. Age and northern European residency are the critical factors that determine heterogeneity in the APOE e4-associated prevalence of SCD.

Association between apolipoprotein E gene polymorphism and mild cognitive impairment: a meta-analysis

A number of published case–control studies reported that the apolipoprotein E (ApoE) gene polymorphism was associated with the mild cognitive impairment (MCI). However, previous reports still remain conflicting. To estimate the association between ApoE polymorphism and MCI susceptibility, we searched the electronic databases including PubMed, Wanfang, CNKI (China National Knowledge Infrastructure), VIP, and EMBASE to retrieve all available studies. A total of 18 studies with 2,004 cases and 3,705 controls were included in this meta-analysis. The pooled analysis based on selected studies showed that statistically significant risk association was found between ApoE gene polymorphism and MCI in overall population (ε4 vs ε3: odds ratio [OR] =2.38, 95% confidence interval [CI]: 2.11–2.68; ε4/ε4 vs ε3/ε3: OR =4.45, 95% CI: 3.06–6.48; ε2/ε4 vs ε3/ε3: OR =2.57, 95% CI: 1.77–3.73; ε3/ε4 vs ε3/ε3: OR =2.31, 95% CI: 1.99–2.69). However, no significant association was detected in two genetic models: ε2 versus ε3 (OR =0.90, 95% CI: 0.77–1.05) and ε2/ε2 versus ε3/ε3 (OR =0.91, 95% CI: 0.50–1.65). Furthermore, ApoE ε2/ε3 genotype provided a slight protection for MCI in overall population (ε2/ε3 vs ε3/ε3: OR =0.80, 95% CI: 0.66–0.97). In the stratified analysis based on ethnicity, similar results were also observed in Chinese population (significant risk: ε4 vs ε3: OR =2.52, 95% CI: 2.19–2.90; ε4/ε4 vs ε3/ε3: OR =5.45, 95% CI: 3.41–8.70; ε2/ε4 vs ε3/ε3: OR =2.59, 95% CI: 1.74–3.86; ε3/ε4 vs ε3/ε3: OR =2.34, 95% CI: 1.97–2.79; slight protection: ε2/ε3 vs ε3/ε3: OR =0.79, 95% CI: 0.64–0.98; no association: ε2 vs ε3: OR =0.92, 95% CI: 0.78–1.09; and ε2/ε2 vs ε3/ε3: OR =1.04, 95% CI: 0.55–1.99). In summary, this meta-analysis of 5,709 subjects suggested that ApoE ε4 allele was associated with an increased risk of MCI. In addition, ApoE ε2/ε3 genotype provided a slight protection for MCI.

A correlativity study of plasma APL1β28 and clusterin levels with MMSE/MoCA/CASI in aMCI patients

Amnestic mild cognitive impairment (aMCI) is a sub-clinical condition characterized by memory deficits that are not severe enough to affect daily functioning. Here we investigated two potential biomarkers found in the cerebrospinal fluid of AD patients, APLP1-derived Aβ-like peptides 28 (APL1β28) and clusterin plasma levels, in terms of their relationship to cognitive function, as reflected in the Mini-Mental State Examination (MMSE), the Montreal Cognitive Assessment (MoCA) and the Cognitive Assessment Screening Instrument (CASI) in aMCI patients. Forty-seven aMCI patients and thirty-five age- and gender-matched healthy adult controls were recruited for this study. Using the ELISA method, we found that the mean concentrations of both APL1β28 and clusterin were not significantly different between the control and aMCI groups. The APL1β28 levels were positively correlated with clusterin and that both were negatively correlated with the MMSE scores of the aMCI patients. Clusterin levels were negatively correlated with the MoCA and CASI scores of the aMCI patients. Using multivariate analysis, the correlation between clusterin and MMSE/MoCA/CASI was independent of other AD risk factors including age, education, sex, body mass index and ApoE genotype. The data presented here demonstrate that plasma clusterin levels reflect cognitive function in aMCI patients.

APOE ε4 Genotype and the Risk for Subjective Cognitive Impairment in Elderly Persons

The authors compared the risk for subjective cognitive impairment (SCI) between carriers of the apolipoprotein E ε4 (APOE ε4) allele (cases) and APOE ε4 noncarriers (controls). SCI was assessed by a validated self-reported questionnaire. The authors used multivariable logistic regression analyses to compute odds ratios and 95% confidence intervals adjusted for age, sex, education, and marital status. Data were available on 114 participants (83 women; 47 APOE ε4 carriers; mean age, 69 years). The risk for SCI was significantly higher among cases than controls, particularly for those 70 years of age and older. These findings should be considered preliminary until confirmed by a prospective cohort study.