Further Cox regression analyses revealed that IHD was associated with a higher risk of diagnostic conversion (HR = 1.321, 95 % CI = 1.003–1.741, p = 0.048), after adjusting for age, sex, education, right handedness, APOE ε4, hypertension, diabetes mellitus, hyperlipidemia, smoking, atrial fibrillation, and heart failure. The gene discussed is APOE; the disease is diabetes mellitus.