What is Life Expectancy?

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Life expectancy refers to the number of years a person is expected to live based on the statistical average. Life expectancy varies by geographical area and by era. In the Bronze age, for example, life expectancy was 26 years, while in 2010, it was 67 years.

In mathematical terms, life expectancy refers to the expected number of years remaining for an individual at any given age. In formulaic terms, life expectancy is denoted  by ex, where, “e” represents the expected number of years remaining and “x” represents the person’s present age.

The life expectancy for a particular person or population group depends on several variables such as their lifestyle, access to healthcare, diet, economical status and the relevant mortality and morbidity data. However, as life expectancy is calculated based on averages, a person may live for many years more or less than expected.

The concept of life expectancy is also applied in ecological studies. Whether life expectancy is being calculated for plants, animals or humans, tables referred to as actuarial tables or mortality tables are used. Taking humans as an example, these tables can predict how likely it is that a person of a given age will die before their next birthday. From here, several points can be can be calculated, including:

  • The person’s probability of surviving to any given age
  • The life expectancy remaining for people of various ages

The oldest age any human has been known to live to is 122 years, the age reached by Jeanne Calment form France. This is referred to as the “maximum life span,” which is the maximum number of years that any human is known to have lived for.

The life expectancy in Swaziland is 49.4 years, while in Japan it is 82.6 years. However, the figure for Japan may be slightly increased due to many infant deaths being counted as stillbirths. In most developing countries such as India and many other Southeast Asian countries, the number of infant deaths is responsible for lowering the overall life expectancy. However, an article published in the “Lancet” suggested that the life expectancy in Japan may be due to factors such as diet, public health and equal opportunities.

Further Reading

Last Updated: Jun 10, 2023

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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  1. Horacio Gerardo Quintero Vega Horacio Gerardo Quintero Vega Mexico says:

    Claro que tiene que ver la función orgánica, pero tiene mas que ver lo psicológico y psícosomatico, cuando se vuelve orgánico. Realice un calculo basado en estos promedios y me dio valores muy acertados al modo de vida humana actual, claro que solo son hipótesis, nada concluyente, gracias por el reporte es interesante.

  2. John Logger John Logger Canada says:

    I like  this interesting post, and human's longevity can be indefinetely extended being discovered by Allen Omton and Serge Dobrow.
    John Logger

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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