We Haven’t Reached the Maximum Human Lifespan Yet
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The world’s oldest recorded person, Jean Louise Calment, died at the age of 122 in 1997.
No one has exceeded her lifespan for 25 years. This, combined with recent reports of declining life expectancy in the U.S. and other countries, has led to speculation that human longevity may have reached a biological limit. But David McCarthy, an assistant professor of insurance and real estate at the University of Georgia Terry College of Business, disagrees.
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“There are big generational differences these reports often obscure,” he said. “In the U.S., for instance, mortality probabilities have indeed risen for people of middle age and younger. But in recent decades, mortality probabilities of older people in the U.S. have been improving faster than they have at any time since the decade following the introduction of Medicare.”
Published in PLOS ONE, McCarthy’s new study analyzes the mortality of older people in 19 countries and how the increase in mortality rates by age differs between cohorts born in different years.
McCarthy’s data show that for people born in the first part of the 1900s, the rate at which mortality increases with age has actually fallen. This suggests the maximum age at death will increase dramatically in the coming decades as surviving members of these cohorts reach advanced old age, McCarthy said.
McCarthy and his former graduate student, assistant professor Po-Lin Wang of the University of South Florida, analyzed vital statistics from 19 industrialized countries and found similar patterns in all. While mortality compression is dominant in most countries up to cohorts born around 1900, mortality postponement appears to dominate for those born between 1910 and 1950. The oldest of these cohorts may regularly live to 120 or beyond.
“As these cohorts attain advanced ages in coming decades, longevity records may increase significantly,” McCarthy said. “Our results confirm prior work suggesting that if there is a maximum limit to the human lifespan, we are not yet approaching it.”
Studying mortality rate changes by cohort (i.e. year of birth) rather than by period (i.e. year of death) yields new insights, according to McCarthy.
“Standard life expectancy calculations, called period-based calculations, are really just summary measures of the mortality rates of a given population in a given year,” McCarthy explained. “They will only be the actual life expectancy of real people if mortality rates never change again.”
Demographers have used these summary measures to show average lifespans increased because more people live longer — not because the oldest people live longer. Cohort-based calculations, which are used in McCarthy’s paper, look at mortality rate changes that real people can expect over their lives, as mortality rates change in the future.
McCarthy’s research shows that recent changes in cohort mortality rates are consistent with ‘mortality postponement,’ where the maximum age at death increases, rather than ‘mortality compression,’ where this age remains fixed, and more individuals live a bit longer. McCarthy’s results show longevity records have not increased because people old enough to have broken longevity records were members of cohorts that did not experience mortality postponement.
“As newer generations reach these advanced ages, we can expect that longevity records will indeed be surpassed,” McCarthy said.
Reference: McCarthy D, Wang PL. Mortality postponement and compression at older ages in human cohorts. PLOS ONE. 2023;18(3):e0281752. doi: 10.1371/journal.pone.0281752.
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