Apolipoprotein E and α1-antichymotrypsin polymorphism in Alzheimer's disease

A recent observation has shown that a common polymorphism in the α₁-antichymotrypsin (ACT) gene modifies the apolipoprotein E (ApoE) ε4-associated Alzheimer's disease (AD) risk identifing the combination of the ACT/AA and ApoE ε4/ε4 genotypes as a potential susceptibility marker for AD. We analyzed the segregation of the ApoE and ACT polymorphism in sporadic and familial AD patients. In none of the sporadic AD patients did we find the combination of the ACT/AA and ApoE ε4/ε4 genotypes. The frequency of ApoE ε4/ε4 homozygosity in the AD sample resulted highest for the ACT/TT genotype (17.6%). Our data fail to confirm any additional association with AD beyond the ApoE ε4 allele with any ACT genotype, suggesting that ACT does not represent an additional risk factor for AD.     

Impact of behavioral subsyndromes on cognitive decline in Alzheimer’s disease: data from the ICTUS study

Behavioral and psychological symptoms of dementia (BPSD) represent common manifestations among patients affected by Alzheimer’s disease (AD). Some reports have recently classified BPSD into specific clusters/subsyndromes exploring the internal structure of the Neuropsychiatric Inventory (NPI). We evaluated whether specific behavioral subsyndromes are associated with worsening cognitive function. Mild to moderate AD patients were recruited from the cohort of the Impact of Cholinergic Treatment USe (ICTUS) study. Neuropsychiatric symptoms were classified in three subsyndromes, identified at baseline, grouping different combinations of NPI items: (1) “psychotic” (“delusions” and/or “hallucinations”); (2) “affective” (“agitation” and/or “depression” and/or “anxiety” and/or “irritability”); and (3) “behavioral” (“euphoria” and/or “apathy” and/or “disinhibition” and/or “aberrant motor behavior”). Mixed model analyses were performed to measure six-monthly changes in the ADAS-Cog score over a follow-up of 2 years, according to these subsyndromes. All analyses were stratified according to AD severity as defined by the Clinical Dementia Rating (CDR). A total of 1,375 AD subjects were recruited. No NPI cluster was found to significantly (p < 0.05) affect the rate of cognitive decline across the 3 CDR classes. Our results suggest that the cognitive course of AD is not substantially influenced by the presence of specific neuropsychiatric phenotypes. Further studies are needed to extend the present findings and identify possible biological and clinical bases for behavioral subsyndromes.     

Serotonin transporter gene polymorphism and BPSD in mild Alzheimer's disease

The purpose of the present study was to confirm an association of functional polymorphism within the serotonin transporter (5-HTT) gene with Alzheimer's disease (AD) and behavioral and psychological symptoms of dementia (BPSD) in mild AD. Apolipoprotein E (ApoE) gene polymorphism and 2 types of functional polymorphism in the 5-HTT gene, 5-HTT-linked polymorphic region (5-HTTLPR) and a 5-HTT variable number of tandem repeats sequence (5-HTTVNTR) were analyzed longitudinally in outpatients with mild AD to find out whether there was a relation between any such polymorphisms and the occurrence of BPSD. No significant differences in genotype distribution or allele frequencies were identified for 5-HTTLPR or 5-HTTVNTR between AD patients and age- and sex-matched non-demented controls regardless of ApoE epsilon4 allele. No significant differences were noted in 5-HTTLPR genotype or allele distributions between AD patients with or without BPSD. However, significant associations were observed between presence of 5-HTTVNTR allele 10 and BPSD or aggressiveness. This difference was independent of the presence of the ApoE epsilon4 allele. As a result, 5-HTT polymorphisms are unlikely to play any substantial role in susceptibility to AD. Conversely, 5-HTTVNTR influences the risk of developing BPSD or aggressiveness and genetic variations in the 5-HTT gene may be involved in the development of symptomatology for mild AD.     

上海市社区人群阿尔茨海默病与载脂蛋白E基因的关联分析

目的探讨上海地区社区老年人群中阿尔茨海默病(AD)与载脂蛋白E(ApoE)ε     

阿耳茨海默性痴呆与血管性痴呆的ApoE基因多态性研究

目的探讨ApoE基因在阿耳茨海默性痴呆（Alzheimer-typedementia,AD）与血管性痴呆（Vasculardementia,VD）患者当中的分布情况,以找出中国人的特点,评价ApoE基因检测在早期预测性诊断中的作用,比较AD与VD在ApoE基因多态性方面的异同。方法采用PCR-RFLP方法,对41例AD、35例VD和30例对照进行ApoE基因型测定。结果小于70岁的AD患者,其ε4等位基因频率大大高于同龄VD组患者和同龄对照组（P＜0.01和P＜0.05）。而≥70岁的AD患者ε4频率明显低于70岁以下AD患者（P＜0.01）。结论（1）ApoEε4与散发性AD之间具有明显相关性,其基因型以4/3为主,而ε4/4相对于国外文献报道要少。（2）AD组ε4等位基因频率高于VD组（P＜0.05）。（3）评价AD发病危险时,年龄因素不容忽视,70岁以下ε4携带者可能具有更高的AD发病危险性。     

Amyloid-β 1-42 levels are modified by apolipoprotein E ε4 in Creutzfeldt-Jakob disease in a similar manner as in Alzheimer's disease

The presence of apolipoprotein E (ApoE) ε4 allele is a risk factor for Alzheimer's disease (AD) and associated with a more pronounced reduction of amyloid-β 1-42 (Aβ1-42) in the cerebrospinal fluid (CSF). Because a decrease of Aβ1-42 and increase of tau protein levels, both important biomarkers for AD, are also reported in Creutzfeldt-Jakob disease (CJD), we analyzed if a similar relationship can be observed in this rapid progressive dementia. Our study included 309 patients with sporadic CJD (147 neuropathologically confirmed and 162 probable cases). We analyzed the role of ApoE ε4 in sporadic CJD (sCJD), in particular the influence on the CSF-markers 14-3-3 protein, tau protein, neuron-specific enolase, S100 protein, Aβ1-42, and Aβ1-40. No differences in the ApoE ε4 allele frequency and ApoE genotype distribution between sCJD and published healthy controls were observed. The ApoE ε4 allele had no effect on disease duration or age at onset. We detected a dose-dependent ApoE ε4 effect on the decrease of Aβ1-42 in sCJD. ApoE ε4 carriers with one ApoE ε4 allele showed significantly reduced Aβ1-42 values (p < 0.0001) in comparison with non-carriers. ApoE ε4 allele is not a risk factor for sCJD but modifies the Aβ1-42 levels in CSF in a similar manner as in AD. Based on our results in sCJD patients, we hypothesize that the ApoE ε4 effect on Aβ1-42 values might not be disease-specific.     

胰岛素样生长因子1、载脂蛋白酶E基因多态性与阿尔茨海默病关系的研究

目的探讨河南省汉族人群胰岛素样生长因子1(insulin like growth factor 1,IGF-1)基因rs972936位点多态性、载脂蛋白酶E(Apo E)基因多态性与阿尔茨海默病(Alzheimer’s disease,AD)之间的相关性。方法选取58例AD患者和126例年龄、性别相匹配的健康对照(ND)者为研究对象,柱层析法提取外周血基因组DNA,采用PCR和基因测序技术检测IGF-1基因rs972936位点及Apo E基因型多态分布,并进行对比分析。结果与ND组比较,AD组IGF-1基因rs972936位点3种基因型分布总体差异有统计学意义(χ~2=6.108,P=0.047),其中AD组中GG基因型的频率高于对照组(70.7%51.6%,χ~2=5.935,P=0.015),G等位基因频率明显高于健康对照组(χ~2=6.502,P=0.011);AD组Apo Eε4等位基因频率可能增加AD的患病风险(OR=2.872,95%CI 1.542~5.351)(P=0.001);Apo Eε4等位基因不影响IGF-1基因rs972936位点的基因型或等位基因的分布频率(P0.05)。结论 IGF-1基因rs972936位点多态性与河南汉族人群AD的发病可能有相关性,其中GG基因型、G等位基因可能是AD发病的独立于Apo Eε4等位基因的危险因素。Apo Eε4等位基因是散发性AD的主要危险因素。     

Total apolipoprotein E levels and specific isoform composition in cerebrospinal fluid and plasma from Alzheimer’s disease patients and controls

The apolipoprotein E (ApoE) ε4 allele is the strongest risk factor of sporadic Alzheimer’s disease (AD), however, the fluid concentrations of ApoE and its different isoforms (ApoE2, ApoE3 and ApoE4) in AD patients and among APOE genotypes (APOE ε2, ε3, ε4) remain controversial. Using a novel mass spectrometry-based method, we quantified total ApoE and specific ApoE isoform concentrations and potential associations with age, cognitive status, cholesterol levels and established AD biomarkers in cerebrospinal fluid (CSF) from AD patients versus non-AD individuals with different APOE genotypes. We also investigated plasma total ApoE and ApoE isoform composition in a subset of these individuals. In total n = 43 AD and n = 43 non-AD subjects were included. We found that CSF and plasma total ApoE levels did not correlate with age or cognitive status and did not differ between AD and non-AD subjects deeming ApoE as an unfit diagnostic marker for AD. Also, whereas CSF ApoE levels did not vary between APOE genotypes APOE ε4 carriers exhibited significantly decreased plasma ApoE levels attributed to a specific decrease in the ApoE4 isoform concentrations. CSF total ApoE concentrations were positively associated with CSF, total tau, tau phosphorylated at Thr181 and Aβ1-42 of which the latter association was weaker and only present in APOE ε4 carriers indicating a differential involvement of ApoE in tau versus Aβ-linked neuropathological processes. Future studies need to elucidate whether the observed plasma ApoE4 deficiency is a life-long condition in APOE ?4 carriers and whether this decrease in plasma ApoE predisposes APOE ?4 carriers to AD.     

Dietary omega 3 polyunsaturated fatty acids and Alzheimer's disease: interaction with apolipoprotein E genotype

Epidemiological studies suggest a protective role of omega-3 poly-unsaturated fatty acids (n-3 PUFA) against Alzheimer's disease (AD). However, most intervention studies of supplementation with n-3 PUFA have yielded disappointing results. One reason for such discordant results may result from inadequate targeting of individuals who might benefit from the supplementation, in particular because of their genetic susceptibility to AD. The ε4 allele of the apolipoprotein E gene (ApoE) is a genetic risk factor for late-onset AD. ApoE plays a key role in the transport of cholesterol and other lipids involved in brain composition and functioning. The action of n-3 PUFA on the aging brain might therefore differ according to ApoE polymorphism. The aim of this review is to examine the interaction between dietary fatty acids and ApoE genotype on the risk for AD. Carriers of the ε4 allele tend to be the most responsive to changes in dietary fat and cholesterol. Conversely, several epidemiological studies suggest a protective effect of long-chain n-3 PUFA on cognitive decline only in those who do not carry ε4 but with inconsistent results. An intervention study showed that only non-carriers had increased concentrations of long-chain n-3 PUFA in response to supplementation. The mechanisms underlying this gene-by-diet interaction on AD risk may involve impaired fatty acids and cholesterol transport, altered metabolism of n-3 PUFA, glucose or ketones, or modification of other risk factors of AD in ε4 carriers. Further research is needed to explain the differential effect of n-3 PUFA on AD according to ApoE genotype.     

A 2-year follow-up of behavioural and psychological symptoms in Alzheimer's disease

BACKGROUND: The aim was to examine the longitudinal occurrence and persistence of behavioural and psychological symptoms of dementia (BPSD) in Alzheimer's disease (AD). METHODS: Following 60 patients with mild to severe AD over a period of 2 years with annual evaluations, the prospective occurrence and persistence of BPSD in AD were determined by using the Behavioural Abnormalities in AD Rating scale (BEHAVE-AD). Clinical and demographic features of the AD patients were analysed for their association with course features of these symptoms. RESULTS: All of the 60 AD patients experienced BPSD at some point during the 2-year period, particularly agitation was present in every patient within this period. 2-year persistence of BPSD in AD was frequently observed in patients with agitation and with depressiveness, with less frequency in patients with anxiety and aggressiveness, but not in patients with delusions or hallucinations. 2-year persistent aggressiveness was associated with older age and more functional impairment. More functional impairment was also related to 2-year non-persistent hallucinations. CONCLUSIONS: Counselling AD patients and their families and tailoring therapeutic strategies should take into account the different modi of BPSD in AD occurring and persisting longitudinally and interacting with functional disturbances.     

An APOE haplotype associated with decreased ε4 expression increases the risk of late onset Alzheimer's disease

This paper addresses a tenet of the literature on APOE, i.e., the relationship between the effects of the ε4, one of the established genetic risk factor for Alzheimer's disease (AD), and its expression levels as determined by APOE promoter polymorphisms. Five polymorphisms (-491 rs449647, -427 rs769446, -219 rs405509, and ε rs429358-rs7412) were studied in 1308 AD patients and 1082 control individuals from the Central-Northern Italy. Major findings of the present study are the following: 1) the variants -219T and ε4 increase the risk for late onset AD (LOAD) when they are both present in cis on the same chromosome (in phase); 2) the correlation between the haplotype (-219T/ε4) and AD risk persists when the data are stratified by age; 3) this haplotype likely anticipates the age of onset of the disease. These data, while confirming the association between -219T and AD, highlight the importance of the phase of the alleles for the observed effects on AD risk, suggesting that this information has to be taken into account when assessing the AD genetic risk. Moreover, the data help to clarify the apparent discrepancy that emerges from the genetic analysis where an SNP characterizing the haplotype responsible for an increased risk for LOAD is coherently associated with a reduced expression of ApoE levels. Our data are compatible with the hypothesis of a complex role of ApoE in the AD pathogenesis, with positive and negative effects occurring concomitantly according to its expression levels and its protein-protein interactions largely unclarified.     

胆固醇酯转运蛋白基因D442G多态位点对阿尔茨海默病易感性的影响及机制分析

目的探讨胆固醇酯转运蛋白（CETP）基因D442G多态位点对阿尔茨海默病（AD）和血清高密度脂蛋白（HDL）水平的影响。方法用限制性片段长度多态性检测107例AD和115名对照D442G和载脂蛋白E（ApoE）的基因多态性,测定其血清HDL水平。结果对照组D442G的DG基因型频率高于AD组;ApoE分层后ApoEε4携带者D442G的DG基因型在对照组的频率高于AD组,而ApoEε4非携带者2组间无统计学差异,ApoEε4携带者的DG基因型的HDL水平高于DD基因型。结论 D442G是AD保护性因素,其机制可能与其对HDL水平的影响有关。     

Presence of ApoE ε4 allele associated with thinner frontal cortex in middle age

The presence of an ApoE ε4 allele (ε4+) increases the risk of developing Alzheimer's disease (AD). Previous studies support an adverse relationship between ε4+ status and brain structure and function in mild cognitive impairment and AD; in contrast, the presence of an ε2 allele may be protective. Whether these findings reflect disease-related effects or pre-existing endophenotypes, however, remains unclear. The present study examined the influence of ApoE allele status on brain structure solely during middle-age in a large, national sample. Participants were 482 men, ages 51-59, from the Vietnam Era Twin Study of Aging (VETSA). T1-weighted images were used in volumetric segmentation and cortical surface reconstruction methods to measure regional volume and thickness. Primary linear mixed effects models predicted structural measures with ApoE status (ε3/3, ε2/3, ε3/4) and control variables for effects of site, non-independence of twin data, age, and average cranial vault or cortical thickness. Relative to the ε3/3 group, the ε3/4 group demonstrated significantly thinner cortex in superior frontal and left rostral and right caudal midfrontal regions; there were no significant effects of ε4 status on any temporal lobe measures. The ε2/3 group demonstrated significantly thicker right parahippocampal cortex relative to the ε3/3 group. The ApoE ε4 allele may influence cortical thickness in frontal areas, which are later developing regions thought to be more susceptible to the natural aging process. Previous conflicting findings for mesial temporal regions may be driven by the inclusion of older individuals, who may evidence preclinical manifestations of disease, and by unexamined moderators of ε4-related effects. The presence of the ε2 allele was related to thicker cortex, supporting a protective role. Ongoing follow-up of the VETSA sample may shed light on the potential for age- and disease-related mediation of the influence of ApoE allele status.     

Apolipoprotein E ε2 does not increase risk of early-onset sporadic Alzheimer's disease

We examined the association of apolipoprotien E (ApoE) genotype and the risk of early-onset Alzheimer's disease (AD) in 209 white early-onset sporadic cases (43% male) and 303 white controls (48% male) of similar age distribution. The risk of AD was significantly increased, relative to the 3/3 genotype, in people with the 4/4, 3/4, and 2/4 genotypes, controlling for age at time of examination and sex. The 2/3 genotype reduced slightly the risk of AD, although the effect was not statistically significant. We conclude, contrary to some previous reprots, that the ApoE ε2 allele does not increase the risk of early-onset sporadic AD.     

阿尔茨海默病精神行为障碍与载脂蛋白E基因研究

目的：了解阿尔茨海默病（AD）精神行为障碍的临床特征以及与载脂蛋白E（ApoE）基因多态性的相关性。方法：共收集AD患者48例，正常对照者50例，采用阿尔茨海默病行为病理评定量表（BEHAVE-AD）进行精神行为测评，用聚合酶链反应法（PCR）进行ApoE基因分型。结果：AD患者在偏执和妄想、幻觉、行为紊乱和攻击行为方面与正常对照组比较差异有显著性；而ApoE基因检查结果显示携带ApoE ε4基因的AD患者精神行为障碍更为明显。结论：ApoE ε4是AD的风险基因，对携带有ApoE ε4的AD患者应早期干预和治疗。     

Donepezil for the treatment of behavioral symptoms in patients with Alzheimer's disease

Behavioral and psychologic symptoms of dementia (BPSD) are common manifestations in mid- and late-stage Alzheimer's disease (AD). Traditional treatments for BPSD are neuroleptics and sedatives, which are not devoid of serious adverse effects. A number of studies show beneficial effects in the treatment of BPSD with acetylcholinesterase inhibitors (AChEI). The present study aimed to evaluate the effect of donepezil (using the generic drug Memorit) as monotherapy for AD patients suffering from BPSD. Twenty-eight consecutive patients followed at the Memory Outpatient Clinic and Psychogeriatric Department of the Abarbanel Mental Health Center were treated with donepezil for 6 months. Starting dose was 5 mg daily during the first 4 weeks and continuation with 10 mg daily thereafter. Treatment effects were evaluated using the Mini Mental State Examination (MMSE), the Neuro-Psychiatric Inventory (NPI), and the Clinical Global Impression of Change Scale (CGIC) caregiver version. Twenty-four of 28 patients completed the study. Of these, five patients needed additional rescue neuroleptic treatment due to incomplete response. The mean dose of donepezil was 9.10 mg/day (median 10 mg/day). The overall NPI improved significantly from 33.4 to 21.2 (p = 0.008). The mean CGIC at study's end was 3.0 (mild improvement). The cognitive scores did not change significantly. When compared to the patients who completed the study, patients who discontinued had higher mean scores on the irritability and agitation subscales of the NPI, they were older, and they had longer disease duration and lower MMSE mean scores. Three adverse events were recorded: one syncope causing a toe phalanx fracture and gastrointestinal complaints that resolved over time in two additional patients. Acetylcholinesterase inhibitors should be considered for the treatment of BPSD before neuroleptic treatment is instituted in AD patients with low levels of irritability and agitation.     

The apolipoprotein E ε4 allele is not a significant risk factor for frontotemporal dementia

Frontotemporal dementia (FTD) is the most common early-onset non-Alzheimer's dementia (non-AD). Although the role of the ε4 allele of apolipoprotein E (ApoE) has been well established in AD, studies of ApoE allele distribution in patients with FTD have produced variable results. We studied 33 rigorously diagnosed FTD patients, including several who wre pathologically confirmed, and compared the fequency of the ε4 allele in patients with FTD with the frequency in those with early-onset AD (EOAD), in those with late-onset AD (LOAD), and in non-demented elderly controls. The frequency of ApoE ε4 was 21% in patients with FTD, significantly less than the ApoE ε4 frequency in those patients with EOAD (38%) and those with LOAD (40%), but not significantly different from the ApoE ε4 frequency in elderly controls (13%).     

The apolipoprotein E gene affects the three-year trajectories of compensatory neural processes in the left-lateralized hippocampal network

Previous cross-sectional studies that investigated the effects of apolipoprotein E (ApoE) ε4 status on hippocampal networks have shown inconsistent results. Aging is a well-known risk factor for Alzheimer’s disease (AD) and could strongly interact with ApoE-related vulnerabilities to affect AD risk. However, no longitudinal data have been published regarding the interaction of the ApoE genotype and aging on hippocampal networks. Fifty-one patients with amnestic-type mild cognitive impairment (aMCI) and 64 matched cognitively normal elderly subjects underwent resting-state fMRI scans and neuropsychological tests at baseline and at a 35-month follow-up. Hippocampal resting-state functional connectivity (FC) data were analyzed utilizing a mixed analysis of covariance with ApoE genotype, time points and disease as fixed factors, controlling for age, sex and years of education. The notable finding was that the FC between the left hippocampus and right frontal regions for ε4 carriers longitudinally increased in the normal subjects, but decreased in aMCI patients, whereas the FC for non-carriers was maintained in normal subjects but increased in aMCI patients. Specifically, the longitudinal increases in hippocampal FC with the right inferior frontal gyrus were positively correlated with the changes in episodic memory test scores in non-carriers with aMCI. The interaction between the ApoE genotype, aging and disease suggested that aging should be considered a key regulator of the impact of the ApoE genotype on the phenotypic variants of AD. These findings also demonstrated that compensatory neural processes were accelerated in genetically high risk individuals, but could be subsequently exhausted with the onset of cognitive impairment.     

Association of apolipoprotein E ε4 (ApoE ε4) homozygosity with psychiatric behavioral symptoms

To examine the relationship between apolipoprotein E ε4 (ApoE ε4) and psychiatric symptoms, we compared ε4/ε4, ε3/ε3, and ε3/ε4 subjects. 659 outpatients with memory complaints underwent comprehensive neuropsychiatric assessment interview and neurological examination and ApoE genotyping: 98 were ε4/ε4. 18.4% (n = 18) ε4/ε4, 19.3% (n = 45) ε3/ε4, and 5.4% (n = 14) ε3/ε3 presented with symptoms of anxiety (p = 0.00001). ε4/ε4 patients with mild cognitive impairment (MCI; p < 0.0001) and those with Alzheimer's disease with late onset (p = 0.0175) were the most frequently affected. For anxiety, there were no gender dependent differences in the two homozygous groups, however, in the ε3/ε4 group, anxiety symptoms were evident in 7.3% (n = 8) of the male versus 30.1% (n = 37) of the female ε3/ε4 heterozygotes (p < 0.0001). Depression was found in 20.4% (n = 20) ε4/ε4 and 21.0% (n = 49) ε3/ε4 compared to 17.1% (n = 44) ε3/ε3 (p = 0.5181). Visual hallucinations were reported in 5.1% (n = 5) ε4/ε4 as opposed to 3.8% (n = 9) ε3/ε4 and 2.3% (n = 6) ε3/ε3 (p = 0.5278). We have seen a higher association of anxiety with the ApoE ε4 allele across all stages of disease and what may be a dosing effect in the early stage (MCI) for this ostensible risk, since we see a significantly higher frequency in the ApoE ε4 homozygotes when compared to the heterozygotes.     

Apolipoprotein E genotype in patients with alzheimer's disease: Implications for the risk of dementia among relatives

Numerous studies have shown that the risk of Alzheimer's disease (AD) is associated with the dose of the ?4 allele of apolipoprotein E (ApoE). However, more than one third of AD patients lack ?4 and many persons having ?4 survive cognitively intact to old age. We evaluated the lifetime risk of disease in 3,999 first-degree relatives of 549 probands who met the criteria for probable or definite AD and whose ApoE genotypes were known. ApoE genotypes for relatives were not determined. After age 65 the risk among relatives was proportional, as much as 7 to 10% at age 85, to the number of ?4 alleles present in the proband. Risks to relatives of ApoE 2/2 and 2/3 probands were nearly identical at all ages to risks for relatives of ApoE 3/3 probands. The expected proportion of relatives having at least one ?4 allele was calculated for each genotype group based on the distribution of parents, sibs, and offspring in the sample. Among relatives in the ApoE 3/3 group, the lifetime risk for AD by age 90 was three times greater than the expected proportion of ?4 carriers, suggesting that factors other than ApoE contribute to AD susceptibility. Furthermore, the 44% risk of AD by age 93 among relatives of ApoE 4/4 probands indicates that as many as 50% of people having at least one ?4 allele do not develop AD. We also found that among male relatives, risk of AD in the ApoE 3/4 group was similar to that for the ApoE 3/3 group but significantly less than the risk for the ApoE 4/4 group. In contrast, among female relatives the risk for the ApoE 3/4 group was nearly twice that for the ApoE 3/3 group and identical to the risk for the ApoE 4/4 group. These findings are consistent with a sex-modification effect of the E4 isoform on disease susceptibility.