Above age 105, the rise in risk of death by age slows - and even plateaus - according to a new study, one that provides valuable insight into one of the most fundamental questions of human aging; Is there a fixed maximum lifespan for humans? Such a limit, if any, has yet to be reached, Elisabetta Barbi et al. go on to conclude following their research, which involved studying data on nearly 4,000 Italians. The demography of aging is a contentious topic with much debate as to whether mortality rates continue to rise exponentially into extreme age or level out into a high plateau (such that the likelihood of dying stays close to constant for those at the relevant age, and beyond). While some studies investigating limits to the rise in risks of death by age have suggested a plateau in mortality, others have reached an opposite conclusion: the better the data, the less the appearance of such a leveling out. In this report, Barbi et al. provide strong evidence for the former case, supporting the existence of mortality plateaus in the oldest-old. In this study, the authors estimated mortality rates from data on carefully documented and verified survival trajectories of 3,836 Italians older than 105 between 2009 and 2015. According to the authors, the high-quality data used allowed for extreme-age mortality estimations with unmatched precision and accuracy, free from the typical issues that have limited earlier extreme-age demographic studies. They found that death rates, which increase exponentially with age, begin to decelerate after 80 years old and then approach a plateau after age 105. Furthermore, the authors show that the mortality rate in those aged over 105 declines slightly across groups born within the same year, strongly suggesting that human longevity is increasing over time. Similar mortality plateau patterns in extreme age are observed in other species, hinting at common structural and evolutionary explanations.
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Journal
Science