AOPEP and Cognitive impairment: LDL-C: low-density lipoprotein cholesterol; HDL-C: high-density lipoprotein cholesterol; TC: total cholesterol; TG: triglycerides; AD: Alzheimer's disease; APO: apolipoprotein; Aβ: beta-amyloid; MCI: mild cognitive impairment; BBB: blood-brain barrier; 24S HC: 24S hydroxycholesterol; 27O-HC: 27O hydroxycholesterol; PC: phosphatidylcholine; PLA2: phospholipase 2