APOE and Cognitive impairment: OR: Odds Ratio; HR: Hazard Ratio; RR: Relative Risk; MCI: Mild Cognitive Impairment; AD: Alzheimer’s Disease; CSF: Cerebrospinal Fluid; APOE ε4: Apolipoprotein E ε4 allele (a genetic risk factor for AD); DEM: Dementia; CDR: Clinical Demntia Rating scale; MMSE: Mini-Mental State Evaluation; NINCDS: National Institute of Neurologic and Communicative Disorders and Stroke; ADRDA: AD and Related Disorders Association; 95% CI: 95% Confidence Interval