I. Introduction
Due to the huge number of elderly population worldwide, many health and government organizations are focusing on their quality of life—from medical, social, and physiological points of view. According to the World Health Organization (http://www.who.int/), there will be 1.2 billion people aged 60 or above by 2025 and 2 billion by 2050. So it is utmost important that we continue working with these groups of population, who are somehow dependent and vulnerable in different aspects.