Apolipoprotein E epsilon4 allele frequency and age at onset of Alzheimer's disease

The age distribution of the epsilon4 allelic form of the apolipoprotein E gene (APOE) was investigated in 630 patients with Alzheimer's disease (AD) with onset age ranging from 35 to 90 years. Overall, mean age at onset in APOE epsilon4 allele bearers was significantly later than that in nonbearers. However, when stratified into early onset AD (EOAD) and late onset (LOAD) groups, mean age at onset in EOAD cases bearing APOE epsilon4 allele was later than that in those EOAD cases without epsilon4 allele, whereas in LOAD mean age at onset in cases bearing APOE epsilon4 allele was earlier than in those without epsilon4 allele. When analysed by decade, it was observed that 37% of the total number of APOE epsilon4 allele bearers, and 43% of total number of cases with APOE epsilon4/epsilon4 genotype fell into the 60-69 years age class. Hence, APOE epsilon4 allele frequency, at 0.44, was highest in the 60-69 years age class, progressively decreasing either side of this age group. APOE epsilon4 allele therefore has its maximum impact between onset ages of between 60 and 70 years.     

Accelerated hippocampal atrophy in Alzheimer's disease with apolipoprotein E epsilon4 allele

Although apolipoprotein E epsilon4 is an established risk factor for Alzheimer's disease, its effect on the rate of progression of Alzheimer's disease remains unknown. The purpose of this longitudinal study was to elucidate whether the rate of hippocampal atrophy is a function of the apolipoprotein E genotypes and severity of disease. Fifty-five patients with probable Alzheimer's disease were the subjects. The annual rate of hippocampal atrophy was determined by using magnetic resonance imaging repeated at a 1-year interval. On a two-way analysis of variance, the effect of the apolipoprotein E epsilon4 allele on hippocampal atrophy was significant, but neither the effect of severity nor the interaction term was significant. In further analysis with one-way analysis of variance, the mean annual rate of hippocampal atrophy was significantly different between the groups of patients with (9.76 +/- 4.27%) and without the apolipoprotein E epsilon4 allele (6.99 +/- 4.24%). Apolipoprotein E epsilon4 dose was significantly correlated with the rate of hippocampal atrophy (rs = 0.277, Spearman rank correlation coefficient), suggesting a gene dose effect. The involvement of the apolipoprotein E epsilon4 allele in the progression of hippocampal atrophy has implications for therapeutic approaches in Alzheimer's disease and should be taken into consideration in longitudinal studies including clinical drug trials.     

Association between apolipoprotein E epsilon4 allele and apathy in probable Alzheimer's disease

OBJECTIVE: There have been inconclusive results to date on the association between the Apolipoprotein E (ApoE) genotype and neuropsychiatric symptoms (NPS) in Alzheimer's disease (AD). We investigated whether ApoE epsilon4 allele is associated with NPS in probable AD. METHOD: Data for 197 subjects with probable AD were analysed. The Neuropsychiatric Inventory was used to evaluate the frequency and severity of NPS. Multiple logistic regression models were used to test the association between ApoE genotype and NPS in AD. RESULTS: The ApoE epsilon3/3 genotype was present in 52.3%, epsilon3/4 in 44.1%, and epsilon4/4 in 3.6% of patients. ApoE epsilon4 carriers showed a higher frequency of apathy than non-carriers. After multiple adjustments, the ApoE epsilon4 allele was significantly associated with apathy. CONCLUSION: Our results suggest a relationship between the ApoE epsilon4 allele and apathy in patients with AD.     

Accelerated memory decline in Alzheimer's disease with apolipoprotein epsilon4 allele

To investigate a possible effect of the apolipoprotein (APOE) epsilon4 allele on memory decline in Alzheimer's disease (AD), we examined 64 AD patients with the APOE epsilon3/3, epsilon3/4, or epsilon4/4 allele using the Alzheimer Disease Assessment Scale-Cognitive subscale (ADAS-Cog) and its subtests at the initial examination and at the 1-year follow-up visit. One-year changes in the scores of the Word Recall subtest, Word Recognition subtest, and total ADAS-Cog were significantly correlated with the number of APOE epsilon4 alleles after controlling for the effects of age, sex, education, test interval, and baseline scores. Findings revealed that APOE epsilon4 allele is related to an accelerated memory decline in AD.     

The apolipoprotein E epsilon4 allele and incident Alzheimer's disease in persons with mild cognitive impairment

Possession of one or more copies of the apolipoprotein E (APOE) epsilon4 allele is a known risk factor for Alzheimer's disease (AD), but it is uncertain whether the epsilon4 allele is associated with disease incidence among persons with mild cognitive impairment (MCI). We addressed this issue with data from the Religious Orders Study. Participants were 181 older Catholic clergy members who met criteria for MCI based on a uniform structured clinical evaluation; 56 (30.9%) had at least one epsilon4 allele. Clinical evaluations, which included clinical classification of dementia and AD, were repeated annually. During a mean of 5.7 years of observation, 79 persons (43.6%) developed AD. In a proportional hazards model that controlled for age, sex, and education, possession of an epsilon4 allele was associated with a 93% increase in the risk of developing Alzheimer's disease (95% CI; 1.02, 2.63). There was a marginally significant reduction in the effect of epsilon4 in older compared to younger participants (p=.053). The results suggest that possession of an epsilon4 allele does increase risk of AD in persons with MCI.     

The apolipoprotein E epsilon4 allele and the response to tacrine therapy in Alzheimer's disease.

The objective of our study was to evaluate the effects of the apolipoprotein E (ApoE) phenotype and gender on the response to tacrine treatment in Alzheimer's disease (AD). ApoE phenotyping was performed on 76 patients treated with tacrine for AD. This group comprised 33 ApoE epsilon4 allele carriers (epsilon4+) and 43 non-epsilon4 carriers (epsilon4-). Patients were treated blindly in relation to the ApoE phenotype, with incremental tacrine dosages ranging from 40 mg/day up to the highest dosage (160 mg) tolerated without side-effects. At least 6 weeks elapsed between each increase. Changes in the scores for the Alzheimer Disease Assessment Scale-Cognitive Component (ADAS-Cog) between baseline and each increment in dosage were assessed in the epsilon4- and epsilon4+ groups. The cut-off point for being considered as responsive to tacrine treatment was a 4-point decrease in the ADAS-Cog score. There was no tendency for the epsilon4- carriers to respond better than the epsilon4+ carriers. When patients were stratified by gender, no differences were found between the effects of the treatment on men and women. Consequently, these results do not support the hypothesis that the ApoE phenotype and gender are predictors of the response to tacrine in AD patients.     

The allele interaction between apolipoprotein epsilon2 and epsilon4 in Taiwanese Alzheimer's disease patients

OBJECTIVE: This study aimed to determine the impact of the present of apolipoprotein epsilon (Apoepsilon) 2 on the relationship between Apoepsilon4 and Alzheimer's disease (AD). METHOD: We examined ApoE genotypes in 428 Taiwanese patients with AD and 807 controls; all participants were older than 65 years. RESULTS: The allele frequency of Apoepsilon4 was greater in AD patients than controls, but significantly lower than in Caucasians. The presence of an epsilon2 allele alone was not associated with lower risk for AD, but the presence of an epsilon2 allele was associated with an epsilon4 allele frequency similar to that of controls. CONCLUSION: The low allele frequency of epsilon4 in persons with an epsilon2 allele suggests that this may be part of the protective effect of epsilon2 against AD.     

Frequency of the apolipoprotein E epsilon 4 allele in a case-control study of early onset Parkinson's disease.

OBJECTIVES: It has been suggested that Parkinson's disease and Alzheimer's disease may share a common or at least overlapping aetiology. The prevalence of dementia among cases of Parkinson's disease is known to be greater than expected in the general population. The frequency of the apolipoprotein epsilon 4 allele in a large case-control study of early onset Parkinson's disease has been examined. METHODS: 215 patients and 212 population based controls were recruited from the Republic of Ireland between 1992 and 1994. Cases had to have disease onset at 55 years or younger and be born after 1925. RESULTS: The frequency of the epsilon 4 allele was almost identical between cases of Parkinson's disease (14.6%) and healthy controls (13.3%). There was no relation between epsilon 4 status and disease onset, disease duration, Hoehn and Yahr score, and disease progression. The frequency of the epsilon 4 allele was not increased among 10 patients with Parkinson's disease with dementia (10.0%) compared with the other patients without dementia (14.8%). There was no association between epsilon 4 allele status and either a history of smoking, family history of dementia, or Parkinson's disease, or being born in a rural area. The odds ratio for the ApoE epsilon 4 allele associated with Parkinson's disease was 1.10 (95% confidence interval (95% CI) 0.68-1.79), adjusting for age group, sex, and residential status. The pooled odds ratio from a meta-analysis of six studies of ApoE epsilon 4 status and Parkinson's disease was 0.94 (95% CI 0.69-1.27). CONCLUSIONS: The results from our study as well as the pooled meta-analysis exclude any important role for ApoE epsilon 4 status in the development of Parkinson's disease. Our results similarly do not support its role either in dementia associated with Parkinson's disease or disease prognosis.     

Depression in Alzheimer's disease might be associated with apolipoprotein E epsilon 4 allele frequency in women but not in men

The association between depression and apolipoprotein E (apoE) was investigated in 137 out-patients with Alzheimer's disease. An ICD-10 diagnosis of depression was found in 21.1% of all patients. There was a good correlation between clinicians' diagnoses and blinded rating by the Montgomery-Asberg Depression Rating Scale (r = 0.70). In male patients, apoE 3/3 was detected in 34.1%, 3/4 in 38.6%, 4/4 in 13.6%, 2/4 in 6.8% and 2/3 in 6.8% of cases. In female patients, apoE 3/3 was detected in 35.5%, 3/4 in 45.2%, 4/4 in 12.8%, 2/4 in 3.2% and 2/3 in 3.2% of cases. When analyzing the variance of gene dosage effect, the frequency of the apoE epsilon 4 allele was significantly increased in depressed women but not in men. This effect remained stable in stepwise regression analysis when depression as the dependent variable was tested against the independent variables age, age of onset, duration of disease, cognitive status and years of school education.     

Association of the apolipoprotein E epsilon4 allele with late-onset depression.

Apolipoprotein E (ApoE) phenotyping was determined in 42 subjects with Alzheimer's disease (AD), 49 with depression, including 26 with early-onset depression (EOD) and 23 with late-onset depression (LOD), and 49 controls. In the EOD group, the frequency of the ApoE epsilon4 allele was not different from the control frequency (p = 0.532) but was significantly lower than in AD (p < 0.001). In the LOD group, the ApoE epsilon4 frequency was significantly higher than in the controls (p = 0.034) but was not different from that in the AD group (p = 0.229). Individuals with ApoE epsilon4 were at greater risk of getting AD (odds ratio, OR = 5.5, 95% confidence interval, CI, 2.0-14.0) or LOD (OR = 6.1, 95% CI, 1.9-19.0) than of EOD (OR = 0.7, 95% CI, 0.2-2.5). These results suggest an association between the ApoE epsilon4 allele frequency and LOD. Patients with LOD could be at risk of developing AD by an epsilon4-dependent pathway.     

Effect of the apolipoprotein E epsilon4 allele on the efficacy and tolerability of galantamine in the treatment of Alzheimer's disease

OBJECTIVE: To investigate the effect of the apolipoprotein E (ApoE) epsilon4 allele on the efficacy and tolerability of galantamine treatment. METHODS: A total of 202 patients with mild to moderate Alzheimer's disease participated in a 16-week, prospective, multi-center, randomized, double-blind galantamine trial in a Korean population. Patients were assessed at baseline and after 4, 8 and 16 weeks of randomized treatment using the 11-item cognitive subscale of the Alzheimer's Disease Assessment Scale (ADAS-cog/11), the Clinician's Interview-Based Impression of Change plus Caregiver Input (CIBIC-plus), the Disability Assessment for Dementia Scale (DAD), the Behavioural Pathology in Alzheimer's Disease Rating Scale (BEHAVE-AD) and adverse events. ApoE genotypes were determined for all subjects. RESULTS: Of the 202 subjects, 115 carried at least one ApoE epsilon4 allele and 87 did not. In both ApoE epsilon4 carriers and ApoE epsilon4 noncarriers, significant improvements were detected relative to baseline on ADAS-cog/11, CIBIC-plus, DAD and BEHAVE-AD. ApoE epsilon4 noncarriers showed better improvement in mean total BEHAVE-AD score and mean psychosis (delusions and hallucinations) subscale score than ApoE epsilon4 carriers. The incidence of weight loss was significantly higher in ApoE epsilon4 carriers (n = 11; 9.6%) than in ApoE epsilon4 noncarriers (n = 1; 1.2%) during this 16-week study, even though 92% of patients who complained of weight loss completed this 16-week trial successfully. CONCLUSION: ApoE epsilon4 genotype does not affect galantamine-related improvements in cognition, global rating, function and behavior. Longer prospective studies with larger patient populations are required to confirm these new findings.     

Apolipoprotein E type 4 allele and Alzheimer's disease: Effect on age at onset and relative risk in different age groups

The effect of the apolipoprotein E (apoE) genotype on the age at onset of Alzheimer's disease (AD) and the relative risk conferred by the apoE 4 allele were studied in 91 patients and 69 healthy age-matched controls. According to the age of presentation, which varied from 44 to 95 years, subjects were divided into four groups. The inheritance of at least one 4 allele was associated with a significant reduction of the age at onset by 7.7 years among patients who were 83 years or older when examined. A weaker inverse relationship between the 4 allele and the age at onset was also observed among patients who were aged 44–63 years at presentation. The effect of the c4 allele was minimal or absent in the two intermediate age categories. The relative risk of AD conferred by the inheritance of at least one £4 allele showed no consistent age-related pattern. The overall risk expressed as an odds ratio was 5.0 (95% CI 2.4–10.5). With respect to the limitations of the study, we tentatively conclude (1) that the effect of the apoE 4 allele on the age at onset is not restricted to AD patients of a particular age, in accordance with current hypotheses on the role of apoE gene products in the biology of AD; (2) that the relative risk of AD associated with the 4 allele is not significantly modulated by age. Although the apoE 4 allele is an important susceptibility factor for AD occurring in middle age as well as in later life, it is of limited value in routine clinical diagnosis and should not be used for predictive testing in asymptomatic individuals.     

Apolipoprotein E epsilon4 allele differentiates the clinical response to donepezil in Alzheimer's disease

The existence of an association between apolipoprotein E (APOE) and Alzheimer's disease (AD) has been reported in several studies. The possession of an ApoE epsilon4 allele is now considered a genetic risk factor for sporadic AD. There has been a growing agreement about the role exerted by the ApoE epsilon4 allele on the neuropsychological profile and the rate of cognitive decline in AD patients. However, a more controversial issue remains about a possible influence of the APOE genotype on acetylcholinesterase inhibitor therapy response in AD patients. In order to address this issue, 81 patients diagnosed as having probable AD were evaluated by a complete neuropsychological test battery at the time of diagnosis (baseline) and after 12-16 months (retest). Patients were divided into two subgroups: (1) treated with donepezil at a dose of 5 mg once a day (n = 41) and (2) untreated (n = 40). Donepezil therapy was started after baseline evaluation. The APOE genotype was determined according to standardized procedures. We evaluated the possible effect of the APOE genotype on the neuropsychological tasks in relation to donepezil therapy. The statistical analysis of the results showed a global worsening of cognitive performances for all AD patients at the retest. Differences in the clinical outcome were analysed in the four subgroups of AD patients for each neuropsychological task. ApoE epsilon4 carriers/treated patients had improved or unchanged scores at retest evaluation for the following tasks: visual and verbal memory, visual attention and inductive reasoning and Mini Mental State Examination. These results indicate an effect of donepezil on specific cognitive domains (attention and memory) in the ApoE epsilon4 carriers with AD. This might suggest an early identification of AD patients carrying at least one epsilon4 allele as responders to donepezil therapy.     

HLA A2 allele is associated with age at onset of Alzheimer's disease

The prevalence of the HLA A2 allele was investigated in a group of Italian patients with sporadic and early-onset familial Alzheimer's disease (AD and FAD) to analyze the potential association of this allele with early age of onset of the disease. The possible interaction between the HLA A2 allele and apolipoprotein E epsilon4 allele was analyzed. Our data suggest that A2 and epsilon4 alleles may have additive effects on AD onset, and that A2 may play an important role in determining or contributing to a very early age at onset. These findings further support the hypothesis of the involvement of an immune/inflammatory mechanism in the pathogenesis of AD.     

Absence of the apolipoprotein E epsilon4 allele is associated with working memory impairment in Parkinson's disease

The apolipoprotein E (APOE) epsilon4 allele has been associated with an increased risk of Alzheimer's disease (AD) and weaker episodic memory among elderly. Although this APOE allele has been linked to earlier onset of Parkinson's disease (PD), an association with dementia in PD has been only inconsistently demonstrated. Given the heterogeneity of cognitive impairment patterns in PD, this study sought to determine whether an association exists between APOE genotype and specific cognitive deficits in PD. The neuropsychological test performance of 42 PD patients without an epsilon4 allele (PD-Non4) and of 20 with at least one epsilon4 allele (PD-epsilon4) was compared to that of 146 elderly control subjects (NC). The PD groups were comparable in overall severity of cognitive impairment and disease duration, but the PD-epsilon4 group was younger, had an earlier disease onset, and contained a higher proportion of persons with dementia. Both PD groups showed wide-ranging cognitive impairments relative to NC. Once age differences between groups were controlled for, the PD groups generally did not differ from each other in cognitive performance. However, only the PD-Non4 group demonstrated working memory/attention impairments (digit span, visual span, Trailmaking test) relative to the NC group. Results suggest that the APOE genotype may influence the cognitive phenotype of PD, and specifically that absence of the epsilon4 allele is associated with working memory impairment. Additionally, results are consistent with prior findings showing an association between the epsilon4 allele and earlier onset of PD and presence of dementia.     

The apolipoprotein E allele epsilon 4 does not correlate with the number of senile plaques or neurofibrillary tangles in patients with Alzheimer's disease.

BACKGROUND AND OBJECTIVES: Apolipoprotein E (apoE) has been implicated in regenerative processes in the brain after trauma, as well as in the pathogenesis of Alzheimer's disease. Inheritance of a specific apo epsilon allele (apo epsilon 4) determines in part the risk and the mean age at onset of Alzheimer's disease. ApoE has been found to bind isoform specifically to beta-amyloid protein, the major component of senile plaques, and to the microtubule associated protein tau, which forms paired helical filaments and neurofibrillary tangles. The aim was to further examine the relation between apo epsilon alleles, especially apo epsilon 4, and the development of neuropathological changes associated with Alzheimer's disease. METHODS: Brains of patients with Alzheimer's disease (n = 44) and vascular dementia (n = 11) and of age matched controls (n = 29) were studied. Senile plaques and neurofibrillary tangles in the hippocampus and frontal cortex were quantified. RESULTS: No correlation was found between the number of apo epsilon 4 alleles and the number of senile plaques and neurofibrillary tangles in the hippocampus or the frontal cortex of patients with Alzheimer's disease, or vascular dementia, or control groups. No significant differences in duration or severity of dementia were found between patients with or. without the apo epsilon 4 allele. No increased frequency of apo epsilon 4 was found in vascular dementia. CONCLUSION AND COMMENT: Although the apo epsilon genotype clearly affects whether Alzheimer's disease will develop or not, the present study suggests that it has no influence on pathology or clinical intellectual status, once the dementia has manifested itself. No increased apo epsilon 4 allele frequency was found in neuropathologically diagnosed patients with vascular dementia in whom concomitant Alzheimer's disease can be excluded.     

The apolipoprotein E epsilon 4 allele increases the risk of drug-induced hallucinations in Parkinson's disease.

To determine whether the apolipoprotein E (APOE) epsilon 4 allele is a risk factor of drug-induced hallucinations in nondemented patients with Parkinson's disease (PD), the proportions of patients with hallucinations in groups with and without the APOE epsilon 4 allele were compared with a chi 2 test. The contribution of the APOE epsilon 4 allele to the occurrence of hallucinations was further evaluated by means of logistic regression models, adjusting for potential prognostic variables. Thirteen (76%) of the 17 patients who had the epsilon 4 allele had visual hallucinations, compared with 20 (23%) of the 88 patients without the epsilon 4 allele (p < 0.0001; odds ratio = 11.05; 95% CI 3.24-37.67). In addition, treatment with dopamine agonists also contributed to an increased risk of hallucinations (p = 0.0011). After adjustment for age, severity of parkinsonism, duration of treatment, dose of levodopa, and treatment with dopamine agonists, the association between the presence of the epsilon 4 allele and the occurrence of visual hallucinations remained significant (p = 0.0003). Nondemented PD patients with the APOE epsilon 4 allele have a high risk of developing drug-induced visual hallucinations. Further studies are needed to evaluate which proportion of these patients will end up developing dementia.     

Lower levels of N-acetylaspartate in multiple sclerosis patients with the apolipoprotein E epsilon4 allele

BACKGROUND: In multiple sclerosis (MS), the epsilon4 allele of apolipoprotein E (APOE epsilon4) has been associated with more rapid clinical worsening and more severe tissue damage on magnetic resonance imaging. OBJECTIVE: To use proton magnetic resonance spectroscopy ((1)H-MRS) to further explore the biochemical changes in the brains of patients with MS associated with APOE epsilon4. DESIGN: A 2-year clinical and (1)H-MRS follow-up cohort study. SETTING: The MS outpatient clinic, Department of Neurology, and Magnetic Resonance Center of Karl-Franzens University. PATIENTS: We performed (1)H-MRS of the central portion of both hemispheres and APOE genotyping in 72 patients (52 women and 20 men; mean +/- SD age, 34.8 +/- 8.8 years) with clinically definite relapsing-remitting MS. Repeated studies were performed in 44 patients after a mean +/- SD interval of 34 +/- 9 months. MAIN OUTCOME MEASURE: Levels of N-acetylaspartate as measured by (1)H-MRS. RESULTS: Patients with MS and an epsilon4 allele (n = 19) had a significantly lower mean +/- SD N-acetylaspartate-creatine ratio than those without an epsilon4 allele (n = 53) (1.73 +/- 0.26 vs 1.89 +/- 0.24; P =.04) despite the absence of significant differences in age at onset, disease duration, Expanded Disability Status Scale score, and number of previous relapses between subgroups. During follow-up, the drop in the N-acetylaspartate-creatine ratio of epsilon4 carriers was also significantly larger (-0.31 vs -0.10; P =.01). This was paralleled by a higher number of relapses (mean +/- SD, 4.1 +/- 2.7 vs 1.7 +/- 1.6; P =.02) and a faster although nonsignificant progression of disability (mean +/- SD (Delta)Expanded Disability Status Scale score, 0.9 +/- 1.8 vs 0.3 +/- 1.1; P =.19). CONCLUSIONS: The APOE epsilon4 allele has a negative effect on the course of MS, and increasing axonal damage may be an important mechanism.     

Single photon emission computed tomography and apolipoprotein E in Alzheimer's disease: impact of the epsilon4 allele on regional cerebral blood flow

The aim of this study was to examine the impact of the apolipoprotein E (APOE) epsilon4 allele on semiquantitative regional cerebral blood flow (rCBF) in Alzheimer's disease. Single photon emission computed tomography technetium (SPECT) with (99m)Tc d,l-hexamethyl propylenamine oxine was used to determine rCBF in 41 consecutive patients (18 males/23 females) with probable Alzheimer's disease according to the National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria (mean age 71.0 years; range 54-85). The mean Mini-Mental State Examination (MMSE) score was 20.4 (range 10-30). After normalization of CBF to mean blood flow in the cerebellum, values for rCBF in several cortical regions of interest, side-to-side asymmetry indices, and anterior-posterior ratios were calculated. Determination of the APOE genotype from blood samples was performed using restriction enzyme polymerase chain reaction technique. Multivariate regression analyses and the Wilcoxon rank-sum test for unpaired data (Mann-Whitney) were used for statistical analysis. The patients comprised 27APOE epsilon4-positive and 14APOE epsilon4-negative individuals. Five patients were APOE epsilon4 homozygotes. APOE epsilon4-positive patients had significantly reduced rCBF in the right frontal and left occipital lobes. On nonparametric analysis, the most prominent differences between epsilon4-negative and epsilon4-positive patients were demonstrated in subregions representing the frontal association cortex (Mann-Whitney, P < .01). Age-stratified analysis suggested that these findings could be demonstrated predominantly in the elderly patients. The results of this study suggest that the APOE genotype in itself may have an impact on the pattern of rCBF deficits in Alzheimer's disease. The more pronounced reduction of rCBF in frontal association cortex observed in elderly APOE epsilon4-positive patients might predict clinical progression.     

Olfactory identification and apolipoprotein E epsilon 4 allele in mild cognitive impairment

To investigate olfactory identification and apolipoprotein E ε4 allele in patients with mild cognitive impairment (MCI), we used Cross-Cultural Smell Identification Test (CC-SIT) from University of Pennsylvania to assess olfactory identification performance and polymerase chain reaction (PCR) to detect apolipoprotein E ε4 (ApoE ε4) allele in 28 patients with MCI and the 30 age-matched control subjects in present study. The Mann-Whitney U test demonstrated that the MCI group performed significantly worse on CC-SIT than the normal aging group (P<0.01). For MCI patients olfaction scores correlated positively with CAMCOG-C (r=0.61, P<0.01), but not with age, gender or years of education. In normal subjects, the CC-SIT score showed no significant associations with age, gender, years of education, or CAMCOG-C. As the least common allele in Chinese, ε4 was found in 13.3% of controls and in 35.8% of MCI in this study. ApoE ε4 was significantly higher in MCI group than normal group (χ²=4.65, P<0.01). There was a significant effect of allele status on odor identification: subjects with ε4 allele were not able to identify as many odors as the subjects without ε4 allele (P<0.01). These results suggested that the decreased olfactory identification in MCI may be a marker for the early diagnosis of Alzheimer’s disease, and ApoE genotype may be part of the basis of olfactory identification decline.