Life expectancy, often abbreviated to LEB (for Life expectancy at birth), is a statistical measure of the average time an organism is expected to live, based on the year of its birth, its current age and other
National LEB figures reported by statistical national agencies and international organizations are indeed estimates of period LEB. In the
Mathematically, life expectancy is the mean number of years of life remaining at a given age, assuming age-specific mortality rates remain at their most recently measured levels. It is denoted by ,[a] which means the mean number of subsequent years of life for someone now aged , according to a particular mortality experience.
Life expectancy is also used in plant or animal
Records of human lifespan above age 100 are highly susceptible to errors. For example, the previous world-record holder for human lifespan, Carrie White, was uncovered as a simple typographic error after more than two decades. Therefore, the capacity for equivalent hidden errors make maximum lifespan records highly dubious. The oldest confirmed recorded age for any human is 122 years, reached by
The following information is derived from the 1961
Life expectancy at birth takes account of
|Era||Life expectancy at birth in years||Life expectancy at older age|
|33||Based on Neolithic and Bronze Age data, the total life expectancy at 15 would not exceed 34 years. Based on the data from modern hunter-gatherer populations, it is estimated that at 15, life expectancy was an additional 39 years (total 54), with a 0.60 probability of reaching 15.|
|20 to 33||Based on Early Neolithic data, total life expectancy at 15 would be 28–33 years|
|26||Based on Early and Middle Bronze Age data, total life expectancy at 15 would be 28–36 years|
|25 to 28||Based on Athens Agora and Corinth data, total life expectancy at 15 would be 37–41 years|
|20 to 30||Data is lacking, but computer models provide the estimate. If a person survived to age 20, they could expect to live around 30 years more. Life expectancy was probably slightly longer for women than men.|
||Average lifespan of scholars was 59–84.3 years.|
|30||At age 21, life expectancy of an aristocrat was an additional 43 years (total age 64).|
|33–40||34 years for males in the 18th century.|
|1900 world average||31|
|1950 world average||48|
|2017 world average||72.2|
Life expectancy increases with age as the individual survives the higher mortality rates associated with childhood. For instance, the table above listed the life expectancy at birth among 13th-century English nobles at 30. Having survived until the age of 21, a male member of the English aristocracy in this period could expect to live:
17th-century English life expectancy was only about 35 years, largely because infant and child mortality remained high. Life expectancy was under 25 years in the early
Human beings are expected to live on average 30–40 years in Eswatini and 82.6 years in Japan, but the latter's recorded life expectancy may have been very slightly increased by counting many infant deaths as stillborn. An analysis published in 2011 in
There are great variations in life expectancy between different parts of the world, mostly caused by differences in
Actual life expectancy in Botswana declined from 65 in 1990 to 49 in 2000 before increasing to 66 in 2011. In South Africa, life expectancy was 63 in 1990, 57 in 2000, and 58 in 2011. And in Zimbabwe, life expectancy was 60 in 1990, 43 in 2000, and 54 in 2011.
In the United States, African-American people have shorter life expectancies than their European-American counterparts. For example, white Americans born in 2010 are expected to live until age 78.9, but black Americans only until age 75.1. This 3.8-year gap, however, is the lowest it has been since 1975 at the latest. The greatest difference was 7.1 years in 1993. In contrast, Asian-American women live the longest of all ethnic groups in the United States, with a life expectancy of 85.8 years. The life expectancy of Hispanic Americans is 81.2 years. According to the new government reports in the USA, life expectancy in the country dropped again because of the rise in suicide and drug overdose rates. The Centers for Disease Control (CDC) found nearly 70,000 more Americans died in 2017 than 2016, with rising rates of death among 25- to 44-year-olds.
Cities also experience a wide range of life expectancy based on neighborhood breakdowns. This is largely due to economic clustering and poverty conditions that tend to associate based on geographic location. Multi-generational poverty found in struggling neighborhoods also contributes. In United States cities such as
Economic circumstances also affect life expectancy. For example, in the United Kingdom, life expectancy in the wealthiest and richest areas is several years higher than in the poorest areas. This may reflect factors such as diet and lifestyle, as well as access to medical care. It may also reflect a selective effect: people with chronic life-threatening illnesses are less likely to become wealthy or to reside in affluent areas. In
A 2013 study found a pronounced relationship between
Life expectancy is also likely to be affected by exposure to high levels of
A paper from 2015 found that female fetuses have a higher mortality rate than male fetuses. This finding contradicts papers dating from 2002 and earlier that attribute the male gender to higher in-utero higher mortality rates. Among the smallest premature babies (those under 2 pounds or 900 g), females have a higher survival rate. At the other extreme, about 90% of individuals aged 110 are female. The difference in life expectancy between men and women in the United States dropped from 7.8 years in 1979 to 5.3 years in 2005, with women expected to live to age 80.1 in 2005. Data from the UK shows the gap in life expectancy between men and women decreasing in later life. This may be attributable to the effects of infant mortality and young adult death rates.
In the past,
Some argue that shorter male life expectancy is merely another manifestation of the general rule, seen in all mammal species, that larger-sized individuals within a species tend, on average, to have shorter lives. This biological difference occurs because women have more resistance to infections and degenerative diseases.
In her extensive review of the existing literature, Kalben concluded that the fact that women live longer than men was observed at least as far back as 1750 and that, with relatively equal treatment, today males in all parts of the world experience greater mortality than females. Kalben's study, however, was restricted to data in Western Europe alone, where demographic transition occurred relatively early. In countries such as Hungary, Bulgaria, India and China, males continued to outlive females into the twentieth century. Of 72 selected causes of death, only 6 yielded greater female than male age-adjusted death rates in 1998 in the United States. With the exception of birds, for almost all of the animal species studied, males have higher mortality than females. Evidence suggests that the sex mortality differential in people is due to both biological/genetic and environmental/behavioral risk and protective factors.
There is a recent suggestion that
In developed countries, starting around 1880, death rates decreased faster among women, leading to differences in mortality rates between males and females. Before 1880 death rates were the same. In people born after 1900, the death rate of 50- to 70-year-old men was double that of women of the same age. Cardiovascular disease was the main cause of the higher death rates among men. Men may be more vulnerable to cardiovascular disease than women, but this susceptibility was evident only after deaths from other causes, such as infections, started to decline. Most of the difference in life expectancy between the sexes is accounted for by differences in the rate of death by cardiovascular diseases among persons aged 50–70.
In developed countries, the number of
In the United States, the number of centenarians grew from 32,194 in 1980 to 71,944 in November 2010 (232 centenarians per million inhabitants).
The mentally ill have been shown to have a 10- to 25-year reduction in life expectancy. Generally, the reduction of lifespan in the mentally ill population compared to the mentally stable population has been studied and documented.
The greater mortality of people with mental disorders may be due to death from injury, from
The life expectancy of people with diabetes, which is 9.3% of the U.S. population, is reduced by roughly ten to twenty years. Other demographics that tend to have a lower life expectancy than average include transplant recipients, and the obese.
Education on all levels has been shown to be strongly associated with increased life expectancy. This association may be due partly to higher income,  which can lead to increased life expectancy. Despite the association, there is no causal relationship between higher education and life expectancy.
According to a paper from 2015, the mortality rate for the Caucasian population in the United States from 1993 to 2001 is four times higher for those who did not complete high school compared to those who have at least 16 years of education. In fact, within the U.S. adult population, those who have less than a high school education have the shortest life expectancies.
Pre-school education also plays a large role in life expectancy. It was found that high-quality early stage childhood education had positive effects on health. Researchers discovered this by analyzing the results of the Carolina Abecedarian Project (ABC) finding that the disadvantaged children who were randomly assigned to treatment had lower instances of risk factors for cardiovascular and metabolic diseases in their mid-30s.