Life expectancy
In demography, life expectancy is a statistical measure of the average, or mathematical expected value, of the remaining lifetime of an individual in the given group. For non-human organisms the term lifespan is often used to indicate the average length of life in a given species.Notice that the life expectancy is heavily dependent on the criteria used to select the group. In countries with high infant mortality rates, the life expectancy at birth is highly sensitive to the rate of death in the first few years of life. In these cases, another measure such as life expectancy at age 10 can be used to exclude the effects of infant mortality to reveal the effects of other causes of death. Usually, though, life expectancy at birth is specified. To calculate it, it is assumed that current mortality levels remain constant throughout the lives of the hypothetical newborns.
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2 Variations in life expectancy in the world today 3 See also 4 External links |
Life expectancy has dramatically improved over the last few centuries of human history. These changes are largely the result of improvements in public health, medicine and nutrition. The greatest improvements have been made in the richest parts of the world, but the same effects are now spreading to other parts of the world as their economies and infrastructure improve.
Basic life expectancy numbers thend to exagerate this growth, however. While before the modern era life expectancy was lower than forty, this was mostly due to extremely high infant and childhood mortality. Before modern medicine if a person did make it to the age of forty they had an average of another twenty years to live.
These improvements continue to confound the predictions of Thomas Malthus, who predicted what is now known as the Malthusian catastrophe which would occur when population growth exceeded the capacity of the world to sustain that population.
The major exception to this general pattern of improvement has been in those countries worst hit by AIDS, principally in Sub-Saharan Africa, which have seen significant falls in life expectancy due to the disease in recent years.
Another exception is Russia and other former USSR republics, hit by market liberalisation, democracy, and destruction of public health infrastructure. Life expectancy of men dropped to 59.9 years (below the official retirement age), of women to 72.43 years (1999).
A further damper on the increase in life expectancy has arisen for developing and developed countries in recent years through the rise of obesity as a major public health issue. The prevalence of obesity is thought to have reduced an even greater potential for life expectancy by contributing to the rise of cancers, heart disease and diabetes in the developed world.
Throughout human history most of the increase in life expectancy arose from preventing early deaths. The maximum life expectancy remained remarkably constant. However, many scientists believe this will not stay true in the future, as it will be possible to revert aging. According to Leroy Hood, the life expectancy in the next three decades will increase by 10-20 years thanks to advances in DNA sequencing and nanotechnology. Some scientists believe that further advances in medical science may push life expectancy even further, effectively making humans immortal.
See also:
There are great variations in life expectancy worldwide, mostly caused by differences in public health, medicine and nutrition from country to country.
There are also variations between groups within single countries. For example, in the US in the early 20th century there were very large differences in life expectancy between people of different races, which have since lessened. There remain significant differences in life expectancy between men and women in the US and other developed countries, with women outliving men. These differences by sex have been reducing in recent years, with men's life expectancy improving at a faster rate than women's.
The damaging effects of habits such as tobacco smoking and other addictions also make a significant difference to life expectancy.
Life expectancy over human history
Variations in life expectancy in the world today
See also
External links