Life Expectancy

Life expectancy is a measurement defined as the number of years a person, at a given age and within a given population, can expect to live. Calculations of life expectancy come from a life table, a demographic measurement tool that describes the pattern and level of mortality for a given population, typically on a cross-sectional basis; that is, as a snapshot in time. While any age can serve as a basis to determine life expectancy, it is the expectation of life at birth (represented within a life table as e0) most commonly presented because it is a summary indicator of mortality conditions across all ages for a given population, is unaffected by the overall age structure of the population, and, as such, is useful in cross-population comparisons. Occasionally, life expectancy at age 1 actually exceeds that at birth, if infant mortality rates are extraordinarily high within a given population.

Life expectancy usually declines with age. According to the National Center for Health Statistics, in 2003 life expectancy at birth for both men and women of all races in the United States was 77.5 years. At age 65, life expectancy was 18.4 years; at age 75, 11.8 years; and at age 85, 6.8 years. These calculations imply a 65-year-old could expect to live until 83, a 75-year-old until age 86, and an 85-year-old until age 91. Generally, in conjunction with declining fertility rates, improvements in life expectancy have resulted in the “graying” of many national populations.

When the first reliable U.S. life-expectancy data were produced between 1900 and 1902, life expectancy at birth was 47.3 years. Much of the increase in life expectancy resulted from decreases in infant and child mortality, which reflects systematic increases in public health interventions such as the development of sewer systems that helped reduce the spread of infectious diseases. As history suggests, social conditions affect life expectancy as do demographic and socio-economic factors such as gender, race, income, and geography. These factors create a range of life expectancies between populations as well as within a given population. Disparities in mortality rates usually result from unequal development among countries, whereas within a given population disparities reflect social inequality or stratification. Life expectancy currently differs dramatically between developed and developing countries, the latter of whose populations lack public health resources and remain subject to high levels of infectious disease. For example, according to the 2006 World Health Report, whereas life expectancy for some women in developed countries can reach as high as 83 years, life expectancy for men in sub-Saharan Africa, where HIV/AIDS and other communicable diseases have significantly lowered life expectancies over the past 10 years, is less than 45 years.

Although the United States has one of the highest overall life expectancies in the world, it actually ranks low among other industrialized countries. Despite spending more on health care than any other industrialized country, the United States ranked 29th in life expectancy in 2006 and 43rd worldwide for infant mortality in 2005. In 2006, a study conducted by the Harvard School of Public Health found that the gap [Page 543]between highest and lowest life expectancy among subgroups in the United States is over 35 years. This considerable gap reflects disparities that result from a combination of socioeconomic factors, including race, gender, income distribution, and geographic location, as well as phenomena such as widely varying rates of HIV infection and homicide and behavioral and cultural barriers to health, leading to increased rates of diabetes, the prevalence of cardiovascular disease, and alcohol-related deaths within specific populations. Further, this gap speaks to structural inequalities that limit access to health insurance and quality medical care, as well as the lack of social policies aimed at reducing socioeconomic differences.

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