Life expectancy

• 1. Introduction

  ›

  Life expectancy is a statistical estimate of the average years of life remaining at a given age, and a single number from it can deceive almost everyone. Consider a society where life expectancy at birth sits at 30. The figure invites a grim picture of a world without old people. Yet in that same society, a child who reaches age 5 might still have 40 years of life ahead. The trick lies in the math. When many infants die, the average at birth plunges, even though survivors often live to a respectable age. This gap between what the number says and what it means runs through the entire subject. Why does a low figure not mean a young death for everyone? How did human survival climb from roughly 24 years in the early Bronze Age to 73.3 worldwide in 2019? Who lives longer, and why does a Frenchwoman who died in 1997 still mark the outer edge of what a human body can do? These questions sit at the center of one of the most misunderstood measures in all of demography.

• 2. The Number That Lies

  ›

  A society with a life expectancy at birth of 40 would have relatively few people dying at exactly 40. Most would die before 30 or after 55. The average sits in a valley between two peaks of death, a fact that defeats casual intuition. In populations with high infant mortality, the figure at birth swings wildly with deaths in the first few years of life. This sensitivity is why the measure can be grossly misinterpreted, fueling the belief that a low figure means few older people. Demographers built a workaround using life expectancy at age 5, written e5, which strips out the effect of infant mortality. It exposes the underlying mortality of everyone past early childhood. The terms around the subject demand the same care. Life expectancy, longevity, and maximum lifespan are not synonymous. Longevity refers to the long lifespan of some members of a population. Maximum lifespan is the age at death of the longest-lived individual of a species. Even the headline figures come in two flavors. Cohort life expectancy is the mean length of life of everyone born in a given year, computable only once all of them have died. Period life expectancy is the mean for a hypothetical group exposed throughout life to one year's mortality rates, and it is the version national agencies actually report.

• 3. Charting The Centuries

  ›

  Human remains from the early Bronze Age point to a life expectancy at birth of around 24, and the climb since then has been neither steady nor uniform. The earliest documented work on the subject came in the 1660s, from John Graunt and the brothers Christiaan and Lodewijck Huygens. Among the Greeks and Romans, about half of all children died before adolescence, and the truly elderly were rare. Those who survived to 30, though, had a reasonable chance of reaching 50 or 60. In the early 19th century, no country on Earth had a life expectancy at birth longer than 40 years. England, Belgium and the Netherlands came closest, each reaching 40 by the 1840s, only to be surpassed by Norway, Sweden and Denmark. The 20th century brought the steepest gains. In the United States, despite a brief drop from the 1918 flu pandemic, the average lifespan rose by more than 30 years, of which 25 are credited to advances in public health. By the 1950 world average of roughly 45.7 to 48 years, Norway led at 72 while Mali sat at merely 26. One vivid outlier predates the modern surge entirely. Samuel de Champlain wrote that among the Mi'kmaq and Huron he met people over 100 years old, a longevity Daniel Paul attributed to low stress and a diet of lean meats, vegetables and legumes.

• 4. The Edge Of Possible

  ›

  Jeanne Calment, a Frenchwoman, holds the longest verified human lifespan, living 122 years and 164 days between the 21st of February 1875 and the 4th of August 1997. Her record defines what demographers call the maximum life span, the upper boundary no human is known to have crossed. Whether a hard ceiling even exists remains contested. Biologists Bryan G. Hughes and Siegfried Hekimi found no evidence for a limit on human lifespan, a conclusion others questioned on the basis of error patterns. A theoretical study counters that maximum life expectancy at birth is capped by a human life characteristic value, written δ, of around 104 years. The distinction matters because it punctures a popular myth. Science author Christopher Wanjek writes bluntly, "Has the human race increased its life span? Not at all. This is one of the biggest misconceptions about old age: we are not living any longer." Anthropologist John D. Hawks pushes back hard. He argues that age-specific mortality rates have fallen across the entire adult lifespan, so a smaller fraction of adults die at 20, at 30, at 40, at 50. In his words, "In every way we can measure, human lifespans are longer today than in the immediate past." History offers individual proof that long lives are not new. Socrates reached 71, Michelangelo 88, John Adams 90, and Saint Anthony the Great a reported 105.

• 5. Maps Of Inequality

  ›

  Spaniards from Madrid can expect to live to 85, while Bulgarians from the region of Severozapaden are predicted to live just past their 73rd birthday. Such gaps trace mostly to differences in public health, medical care, and diet. The starkest contrasts hide inside single cities. In Glasgow, life expectancy for males in the heavily deprived Calton area stands at 54, fully 28 years less than in the affluent area of Lenzie, which sits only 8 km away. In American cities such as Cincinnati, the gap between low-income and high-income neighborhoods touches 20 years. Africa's story is its own. Over the last 200 years the continent's countries generally have not matched the mortality improvements seen in Asia, Latin America, and Europe, an absence made vivid by AIDS. United Nations projections in 2002 estimated that without HIV/AIDS, Botswana's life expectancy for 2010 to 2015 would have been 70.7 years rather than 31.6. Wealth carries its own surprises. A study in the American Geriatrics Society found that Chinese emperors from the Qin Dynasty to the Qing averaged just 41.3 years, far below the Buddhist monks at 66.9 and the emperors' own servants at 71.3. The COVID-19 pandemic, the World Health Organization announced, reversed the steady global gain in life expectancy and wiped out nearly a decade of progress.

• 6. America's Reversal

  ›

  In 2024, average life expectancy at birth in the United States reached 79.0 years, a record high, with 76.5 for men and 81.4 for women. The US Centers for Disease Control and Prevention credited a 0.6-year rise that year largely to a decline in fatal drug overdoses. The road there was rough. Average life expectancy was 76.4 years in 2021 after declining two years running, the first two-year drop recorded in the country since 1961 to 1963. From 2019 to 2022, the COVID-19 pandemic accounted for roughly 61% of the total decrease, with unintentional injuries, heart disease, homicide, and diabetes adding 11.7%, 5.8%, 2.9%, and 2.8%. The figures also split sharply by group. White Americans in 2010 were expected to live until 78.9 and Black Americans until 75.1, a 3.8-year gap that was the smallest since at least 1975, down from a peak of 7.1 years in 1993. Asian American women live the longest of all groups at 85.8 years. The international comparison stings most. The gap between the United States and peer industrialized countries widened from 0.9 years in 1980 to 4.1 years in 2023. Researchers counted 14.7 million "missing Americans" from 1980 to 2023, deaths that would not have happened at the mortality rate of wealthy nations, including 622,534 in 2019 alone.

• 7. Why Women Outlive Men

  ›

  About 90% of individuals aged 110 are female, the most extreme expression of a gap that holds across the modern world. The difference persists despite women having higher morbidity rates, a contradiction known as the health survival paradox. The gap is not fixed. In the United States it narrowed from 7.8 years in 1979 to 5.3 years in 2005, when women were expected to live to 80.1. Most of the difference between the sexes traces to deaths from cardiovascular disease among people aged 50 to 70. The explanations span behavior and biology. Historically men consumed more tobacco, alcohol, and drugs, and they die more often from injuries, both unintentional and intentional. Of 72 selected causes of death, only 6 produced greater female than male age-adjusted death rates in the United States in 1998. Genetics may push the same direction. One idea points to mitochondria, inherited only through the mother, so that mutations shortening male lifespan are not weeded out by selection acting on females. Another is the unguarded X hypothesis, which holds that a Y chromosome cannot shield a male from harmful genes on the X, while a second X in females can. Kalben concluded the female advantage was observed at least as far back as 1750, though her study was restricted to Western Europe.

• 8. The Code And The Clock

  ›

  The heritability of lifespan is estimated at less than 10%, meaning most variation in how long people live comes from environment rather than genes. Still, specific stretches of the genome leave their mark. A genome-wide association study of 1 million lifespans found 12 genetic loci that shaped survival by changing susceptibility to cardiovascular and smoking-related disease. The locus with the largest effect is APOE, where carriers of the ε4 allele live roughly one year less per copy, mainly through a raised risk of Alzheimer's disease. In July 2020, scientists identified 10 genomic loci with consistent effects across healthspan, lifespan, and longevity, spotlighting haem metabolism and suggesting that high iron in the blood likely shortens healthy years of life. Comparisons across species sharpen the picture. The ability of skin fibroblasts to repair DNA after UV irradiation, measured in shrew, mouse, rat, hamster, cow, elephant and human, rose systematically with species life span. A separate line of work centers on diet. Caloric restriction in mice and rats shows a near doubling of life span from very limited intake, and lower basal metabolic rate has been tied to longer life, the key to why giant tortoises endure. These threads feed a newer ambition. Since 2001 the World Health Organization has tracked healthy life expectancy, or HALE, the years a person can expect in full health, and the 2010s pursuit of a longer healthspan now reaches toward fasting, exercise, and senolytic drugs.