The Japanese population is aging very rapidly. In 2009, the
average lifespans of a Japanese male and female were
79.59 and 86.44 years, respectively, among the highest
lifespans in the world. Moreover, people aged 65 years or
older accounted for 22.7 % of the Japanese population in
2009. Japanese society could be considered a super-aged
society. By 2055, the elderly are expected to account for
40.5 % of the country’s total population [1].