To account for the potential effects of co-morbidities on plasma apoE levels, we first assessed whether there was any difference in the occurrence of coronary artery disease (CAD), congestive heart failure (CHF), hypertension, hyperlipidemia, atrial fibrillation (Afib), diabetes, stroke/transient ischemic attack (TIA), cancer, chronic renal failure, and chronic obstructive pulmonary disease (COPD) between the diagnostic groups (controls, AD, and MCI patients) and between study subjects that were male/females, BAA/NHW and APOE ε4 carriers versus non-carriers. This evidence concerns the gene APOE and atrial fibrillation.