Aging and Health

In the past century, economically developed nations experienced unprecedented changes in the age structure of their populations, as a result of improved public health measures and medical advances that extended life expectancy. Throughout human history there have always been individuals who lived to an advanced age, but such survival was unusual before the twentieth century. During the twentieth century, life expectancy increased markedly and birth rates declined, ushering in an era of dramatic societal aging among developed nations. Since 1900, for example, the total population of the United States tripled in size, but the population of people over age 65 grew 11-fold (National Center for Health Statistics [NCHS], 1999a, 1999b). Average life expectancy at birth in the United States was 49.24 years in 1900, whereas it is now 74.8 years for men and 80.1 years for women (Hoyert, Kung, & Smith, 2005). Similarly, in 1900 only 4% of the population in the United States was greater than 65 years of age, but that figure has risen to 12.4% and is expected to climb to 20% by the year 2030 (American Administration on Aging [AAA], 2001). With the overall growth of the population, these percentage increases represent a very substantial, and still expanding, increase in the absolute numbers of people living to age 65 and beyond.