Participants

We recruited 372 patients with sLOAD (mean age at onset was 72.42 ± 7.82 years) from the outpatients and inpatients of the Department of Neurology, Xiangya Hospital, Central South University, and 345 cognitively healthy individuals (mean age at onset was 70.58 ± 5.34 years) from a community in Changsha. Mini-Mental State Examination (MMSE) scores were used to assess the cognitive ability of the cognitively healthy individuals. Their MMSE scores were equal or above 26 points (Table 1). The sLOAD patients met the National Institute on Aging/Alzheimer’s Association criteria for probable AD (McKhann et al., 2011). The courses of cognitive impairment for patients with sLOAD were over 6 months. The scores of the modified Hachinski ischemia scale were all less than 4. All selected participants were of southern Han Chinese descent, mainly from the provinces of Hunan, Jiangxi, Guizhou, and Guangxi provinces. Participants with causative mutations for AD (APP, PSEN1, and PSEN2) were excluded by Sanger sequencing. Additionally, we did not enroll the AD patients with secondary AD causes, such as vitamin deficiency, hypothyroidism, HIV, and syphilis infection. Patients with cerebral diseases and other neurological diseases were also excluded. This study was approved by the Ethics Committee of Xiangya Hospital of the Central South University (equivalent to an institutional review board). Written informed consent was obtained from each participant or their legal representatives.

Demographic data and neuropsychological assessment of the subjects.