The prevalence of dementia is increasing due to the aging of the population worldwide; the proportion of people aged 65 years or older is expected to be approximately 16% of the world population by 2050. It is estimated that approximately 100 million people will suffer from dementia (Prince et al. 2013; United Nations Population Division 2002). Therefore, the social cost of dementia is increasing annually, and early detection and preventive treatment are challenging.