In many countries of the world, populations are aging at anincreasing rate, as fertility rates decline and life expectancy rises[1]. As a result, the population ratio of older adults relative to thetotal population is increasing. According to a report released by theUnited Nations, the proportion of persons aged 60 years and older,compared to the total population, is expected to double between2007 and 2050, and reach 2 billion by 2050 [2].