What do the terms life expectancy, lifespan, longevity and health span mean?

Although some of these terms sound interchangeable, it is important to know the exact definition: Life expectancy is the amount of time a person is expected to live based on the year they were born, their current age and various demographic factors, including gender. It is always statistically defined as the average number of years of life remaining at a given age. So life expectancy is basically the average lifespan of a population. In contrast, maximum lifespan is the maximum time that one or more members of a population have been observed to survive between birth and death. The oldest woman in the world lived to over 122 years old, so the maximum human lifespan is often given as 120 years [Dong et al. 2016]. The term longevity describes the ability to live a long life beyond the species-specific average age at death [De Benedictis & Franceschi 2006]. Longevity can be considered as the average lifespan under ideal conditions. The term healthspan describes the period of time during which a person is healthy within his or her lifespan. The healthspan is therefore shorter or at most as long as the lifespan, and a person can fall ill early in life but still live for several years [Kaeberlein 2018].

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