Abstract
ObjectivesTo describe the distribution of apolipoprotein E (APOE) genotypes among an elderly Chinese patient population with memory complaints treated in a memory clinic in Beijing and to compare the ε4 allele frequency among individuals with subjective cognitive impairment (SCI), mild cognitive impairment (MCI) and Alzheimer's disease (AD).MethodsA total of 385 subjects with memory complaints participated in the study, including 216 patients with AD, 56 with MCI, 17 with SCI, and 96 with other types of cognitive impairment. A total of 75 healthy elderly control subjects were also recruited. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique was used to investigate the APOE genotypes.ResultsThe frequency of the ε4 allele was 19.6 percent for the entire sample of patients who had memory complaints. The APOE allele distribution differed between women and men (22.6% and 14.9%, respectively; p<0.05) in the individuals with memory complaints. Compared with the control group (7.3%), the prevalence of the APOE ε4 allele was significantly higher in the AD (23.6%) and MCI (21.4%) groups and was slightly increased in the SCI (14.7%) group.ConclusionsIn the memory clinic, we observed a higher prevalence of the APOE ε4 allele among Chinese AD and MCI patients. A similar trend was observed in patients with SCI. These findings suggest that nondemented APOE ε4 allele carriers with memory complaints may have a greater genetic risk for AD and should be monitored more closely.
Highlights
The apolipoprotein E (APOE) e4 allele is the most established genetic risk factor for sporadic Alzheimer’s disease (AD) [1,2]; its presence increases the risk for developing AD at a younger age in a gene-dose dependent manner [3]
Several previous studies have reported that the prevalence of the APOE e4 allele was higher among patients with mild cognitive impairment (MCI), AD and other types of dementia compared with the general population [12,13]
The age at first visit to the memory clinic was higher in the AD group compared with the control group (p, 0.01)
Summary
The apolipoprotein E (APOE) e4 allele is the most established genetic risk factor for sporadic Alzheimer’s disease (AD) [1,2]; its presence increases the risk for developing AD at a younger age in a gene-dose dependent manner [3]. Previous neuropsychological studies have shown that patients with AD [4,5,6,7,8,9,10] and mild cognitive impairment (MCI) [11] who are APOE e4 carriers perform worse on memory tasks. Several previous studies have reported that the prevalence of the APOE e4 allele was higher among patients with MCI, AD and other types of dementia compared with the general population [12,13]. Healthy elderly patients with subjective cognitive impairment (SCI) who do not show any evidence of cognitive impairment on formal testing [17] are 4.5 times more likely to progress to the more advanced memory loss stages of MCI or dementia than patients without SCI [18,19]. It is extremely important to identify potential risk factors for the future development of AD so that these patients can receive closer monitoring in memory clinics
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