Life expectancy

Period LEB is the mean length of life of a hypothetical cohort[3][4] assumed to be exposed, from birth through death, to the mortality rates observed at a given year.

[7] A combination of high infant mortality and deaths in young adulthood from accidents, epidemics, plagues, wars, and childbirth, before modern medicine was widely available, significantly lowers LEB.

[44] English life expectancy at birth averaged about 36 years in the 17th and 18th centuries, one of the highest levels in the world although infant and child mortality remained higher than in later periods.

[b] An analysis published in 2011 in The Lancet attributes Japanese life expectancy to equal opportunities, excellent public health, and a healthy diet.

In what has been described as a "life expectancy crisis", there were a total of 13 million "missing Americans" from 1980 to 2021, deaths that would have been averted if it had the standard mortality rate of "wealthy nations".

[72] In contrast, Asian American women live the longest of all ethnic and gender groups in the United States, with a life expectancy of 85.8 years.

Japan's high life expectancy can largely be explained by their healthy diets, which are low on salt, fat, and red meat.

[81] The authors suggest that when people are working at a more extreme degree during prosperous economic times, they undergo more stress, exposure to pollution, and the likelihood of injury among other longevity-limiting factors.

Other factors affecting an individual's life expectancy are genetic disorders, drug use, tobacco smoking, excessive alcohol consumption, obesity, access to health care, diet, and exercise.

Traditional arguments tend to favor sociology-environmental factors: historically, men have generally consumed more tobacco, alcohol, and drugs than women in most societies, and are more likely to die from many associated diseases such as lung cancer, tuberculosis, and cirrhosis of the liver.

[14] 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.

United Nations statistics from mid-twentieth century onward, show that in all parts of the world, females have a higher life expectancy at age 60 than males.

[85] One recent suggestion is that mitochondrial mutations which shorten lifespan continue to be expressed in males (but less so in females) because mitochondria are inherited only through the mother.

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.

[100] In July 2020, scientists identified 10 genomic loci with consistent effects across multiple lifespan-related traits, including healthspan, lifespan, and longevity.

[111][112][113][114][115] The greater mortality of people with mental disorders may be due to death from injury, from co-morbid conditions, or medication side effects.

[123][124][125] As of 2020 and the COVID-19 pandemic, researchers have found an increased risk of death in the mentally ill.[126][127][128] The life expectancy of people with diabetes, which is 9.3% of the U.S. population, is reduced by roughly 10–20 years.

[134] 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[dubious – discuss] for those who did not complete high school compared to those who have at least 16 years of education.

Researchers discovered this by analyzing the results of the Carolina Abecedarian Project, 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.

One theory is that if predation or accidental deaths prevent most individuals from living to an old age, there will be less natural selection to increase the intrinsic life span.

[139][140] One prominent and very popular theory states that lifespan can be lengthened by a tight budget for food energy called caloric restriction.

[141] Caloric restriction observed in many animals (most notably mice and rats) shows a near doubling of life span from a very limited calorific intake.

[145] Studies of humans with life spans of at least 100 have shown a link to decreased thyroid activity, resulting in their lowered metabolic rate.

[citation needed] The ability of skin fibroblasts to perform DNA repair after UV irradiation was measured in shrew, mouse, rat, hamster, cow, elephant and human.

For an extinct or completed cohort (all people born in the year 1850, for example), it can of course simply be calculated by averaging the ages at death.

While the data required are easily identified in the case of humans, the computation of life expectancy of industrial products and wild animals involves more indirect techniques.

[156][157] Since 2004, Eurostat publishes annual statistics called Healthy Life Years (HLY) based on reported activity limitations.

The United States uses similar indicators in the framework of the national health promotion and disease prevention plan "Healthy People 2010".

Besides the benefits of keeping people healthier longer, a goal is to reduce health-care expenses on the many diseases associated with cellular senescence.

[164] Further, there are many examples of people living significantly longer than the average life expectancy of their time period, such as Socrates (71), Saint Anthony the Great (105), Michelangelo (88), and John Adams (90).