In recent years, all western industrialized countries, and to a growing extent
even many developed and developing Asian nations, have witnessed a remarkable
growth in numbers of older people [1]. Future projections anticipate continued
increases, particularly in numbers of individuals who are 85 years and older [1].
Although US statistics have indicated recent declines in disability trends [2], overall
numbers of older individuals living with disability and functional dependence
are likely to increase given projected increases in life expectancy [3]. For example,
average life expectancy for women born today in the United States is nearly 80, for
men, it is nearly 75 [1]. With these considerations in mind, many investigators have
begun to pay increasing attention to identifying factors which may predict the
transition from health and independence to disability and dependence in older
individuals, eventually providing useful targets for interventions [3, 4].