Super-Centenarians and the Plateau of Mortality
The lady pictured here is Jenne Calment, who lived until the grand age of 122; the world's oldest person.
The phenomenon of super-centenarians—individuals who live beyond the age of 110—challenges our understanding of human longevity and mortality. A fascinating study led by Elisabetta Barbi, which examined the records of 3,800 Italians aged 105 and older, provides intriguing insights into the mortality patterns of these exceptionally aged individuals. This research supports a theory that after reaching an advanced age, the likelihood of dying stabilizes, rather than continuing to increase. This finding challenges the commonly held belief in the Gompertz Law of mortality, which suggests that the risk of death accelerates exponentially with age.
Gompertz Law and the Ageing Population
The Gompertz Law, formulated by Benjamin Gompertz in 1825, is a mathematical model that describes the increase in mortality rate as people age. According to this law, the mortality rate doubles approximately every eight years after the age of 30. This exponential increase suggests that the older an individual becomes, the higher their risk of death. This model has been instrumental in understanding aging and has been observed across various populations and species. However, the Gompertz Law primarily applies to the period of life up until around 90-100 years of age, beyond which mortality rates are less well understood.
Barbi's Study and the Mortality Plateau
Barbi's study, published in the journal Science, offers a fresh perspective by focusing on individuals aged 105 and older—a group often underrepresented in longevity research. By analysing Italian records from 2009 to 2015, the study found that while mortality rates indeed rise sharply with age up to about 105, they then plateau. Specifically, the annual probability of dying stabilises at around 50% for super-centenarians. This suggests that once individuals reach this age, their chance of surviving each subsequent year does not increase, contradicting the predictions of Gompertz Law at extreme ages. This plateau effect has been noted in other studies as well (such as those referred to in the footnote), though Barbi's research provides one of the most comprehensive analyses to date. The study suggests that beyond a certain age, the biological factors contributing to mortality may not intensify as rapidly as previously thought, possibly due to a "survival of the fittest" effect, where only the most robust individuals reach such advanced ages.
Implications and Future Research
The implications of Barbi's findings are significant for the study of aging and longevity. They challenge the inevitability of the Gompertzian increase in mortality and open new avenues for research into the biological mechanisms that allow some individuals to achieve extreme longevity. Understanding why the mortality rate plateaus could provide insights into how to extend healthy lifespan and combat age-related diseases. Future research could explore genetic, lifestyle, and environmental factors that contribute to this mortality plateau. Additionally, studying larger and more diverse populations of super-centenarians can help validate these findings and offer a more global perspective on aging. In conclusion, the study of super-centenarians reveals that after reaching an extreme age, the risk of dying does not continue to climb as steeply as predicted by traditional models like the Gompertz Law. This discovery not only reshapes our understanding of aging but also highlights the remarkable resilience of the human body at its limits. As research in this area progresses, it may unlock new strategies for promoting health and longevity in the broader population.
Other studies
The Evolution of late life (Rauser, Mueller and Rose, 2006)
Demographic analysis of ageing and longevity (Vaupel and associates, 1998)
The relationship between increasing life expectancy and healthy life expectancy (Jean-Marie Robine and Carol Jagger, 2005)