There are biological and epidemiological risk factors of disease progression from MCI to dementia have been identified, including apolipoprotein E4 (APOE-e4), depression, loneliness, hearing impairment, diabetes, hypertension, older age, female gender, and stronger cognitive impairment as reflected by lower MMSE score or higher AD assessment scale cognitive subscale (ADAS-cog) score (13). This evidence concerns the gene APOE and major depressive disorder.