<P> It is important to note that the statistic is usually based on past mortality experience and assumes that the same age - specific mortality rates will continue into the future . Thus, such life expectancy figures need to be adjusted for temporal trends before calculating how long a currently living individual of a particular age is expected to live . Period life expectancy remains a commonly used statistic to summarize the current health status of a population . </P> <P> However, for some purposes, such as pensions calculations, it is usual to adjust the life table used by assuming that age - specific death rates will continue to decrease over the years, as they have usually done in the past . That is often done by simply extrapolating past trends; but some models exist to account for the evolution of mortality like the Lee--Carter model . </P> <P> As discussed above, on an individual basis, a number of factors correlate with a longer life . Factors that are associated with variations in life expectancy include family history, marital status, economic status, physique, exercise, diet, drug use including smoking and alcohol consumption, disposition, education, environment, sleep, climate, and health care . </P> <Table> <Tr> <Td> </Td> <Td> This section does not cite any sources . Please help improve this section by adding citations to reliable sources . Unsourced material may be challenged and removed . (June 2015) (Learn how and when to remove this template message) </Td> </Tr> </Table>

Average number of years that a person born in a particular year can expect to live