A total of 156 elderly people (male/female = 61/95) with normal cognitive function were included in the study. Sampling methods and processes have been described in detail in our previous study 18. All participants met the following criteria: Han Chinese, aged 60 and over;
2) normal cognitive ability; 3) without major medical abnormalities (e.g. cancer and infection); 4) without serious mental illness (e.g. schizophrenia, and dementia); 5) willing to cooperate. A standardized questionnaire was utilized to collect these participants’ general information (for example, age and education), daily living habits (smoking and drinking) and medical conditions (diabetes and hypertension).What’s more, a completion of physical examinations, MRI scans and laboratory tests were also obtained for each subject.
All participants gave written consent to participating in this study. And the study was approved by the Research Ethical Committee of the affiliated mental health center of Shanghai jiaotong university school of medicine.
Clinical Assessment and Cognitive Assessment
The Neuropsychological Test Battery [consists of Digit span19 (assess attention, working memory and executive function), Verbal fluency20 (measure language ability related to executive function), Auditory verbal learning test21 (assess learning ability, recognition memory and delayed free recall), Associative learning and visual identification test22 (assess visual attention and processing speed), Webster picture completion23 (evaluate executive function) and Webster block design24 (assess visuospatial and executive function)] and the Montreal Cognitive Assessment (MoCA)25 were used as tools to assess their specific cognitive domains and global cognitive ability, respectively.
APOE genotype and blood lipids
Genomic DNA was extracted from peripheral blood (Morning fasting whole blood) by using a Blood Genomic DNA Extraction Kit (Qiagen NV, Venlo, the Netherlands). APOE genotype was determined by allele-specific polymerase chain reaction (PCR) methodology26. Then these 156 subjects were divided into three groups according to different genotypes, APOE E2 (ε2/ε2 and ε2/ε3, n=25), APOE E3 (ε3/ε3, n=106), and APOE E4 (ε2/ε4, ε3/ε4, and ε4/ε4, n=25). Table1 presents the detailed distribution of APOE genotypes. In addition, all participants were also tested for plasma glucose, cholesterol, triglycerides, high density lipoprotein and low density lipoprotein.
Continuous variables were expressed as mean ±SD and categorical variables were expressed as frequencies (%). One sample Kolmogorov-Smirrnov test was used to test whether the data conform to a normal distribution. Chi square test was utilized to compare categorical variables. One-way analysis of variance (ANOVA) Least—Significant Difference (LSD) was used to compare the differences among the APOE E2 group, APOE E 3 group, and APOE E 4 group (normal distribution data); while Kruskai-Wallis H test was used to compare data of non-normal distribution among three groups. Two-tailed tests were utilized in a significance level of P<0.05 for all analyses. All statistical analyses were performed using SPSS 22.0 (IBM Corporation, Armonk, NY, USA).