I point out this open access paper not for the content, but for the preamble, in which the author offers a view on why the research community should study aging. Not to learn how it works, but to learn how to intervene in order to make the world a better place, in which people suffer less than is presently the case. This, at root, is why we work on treating aging as a medical condition - because it is by far the greatest source of suffering and death in the world.
Aging is characterized by the progressive deterioration of the body's physiological function, which leads to decreased health, increased incidence of degenerative diseases and, finally, a progressive increase in the risk of death. Aging is classically approached as an inevitable phenomenon whose problems are treated in a timely and palliative way, aiming only to minimize the suffering of the elderly or extend their life span. In addition, these illnesses, usually manifested by chronic diseases associated with aging, tend to be treated individually. That is, individuals with cancer will be treated to eliminate the tumor, while diabetics will be treated with drugs to lower blood glucose levels. As much as it is obvious that these people should be treated, these treatments are still palliative, since even with the cure of one of these diseases, the elderly individual continues to be at an increased risk for other diseases that will inevitably kill them. That is why the main health agencies in the world started to approach aging itself as a clinical entity that deserves to be treated as such. Not by chance, the first clinical study that aims to delay aging itself has recently started.
The impact of having aging as a target for treatment is enormous, not only because aging is the main risk factor for death among humans, but also because it tends to be one of the main expenses of elderly individuals and governments, and it is potentially a major cause of social inequality. If health systems maintain their current policy, public health costs are expected to double by 2050, creating a burden that many countries will not be able to sustain. In addition to health gains, intervening with aging would represent savings of approximately 7 trillion US dollars over 50 years in the US alone, while disease retardation scenarios would lead to minimal savings, since the risk of individuals acquiring other chronic disabling diseases remain.
But is it even possible to delay the aging process itself, or even reverse it as some propose? In 2016, it was suggested that there is a maximum limit to human life span, and that this limit is around 115 years old. This article, however, has been challenged in regard to the statistical analysis, and some are convinced that the proposed limit on human longevity proposed is not real. In fact, a more recent study of Italian centenarians showed that, surprisingly, the risk of death stops increasing with time when individuals reach the age of 105 years. The progressive increase in the risk of death is what characterizes the aging process in living beings. Thus, eliminating this increase means, in practice, that aging stops happening after a certain age. According to the study, at 105 years of age, the chance of death remains fixed at around 50% per year. This leads to the conclusion that at a given moment the balance between damage and repair stabilizes, preserving vital functions as they are, ceasing, however without reversing, the aging process. Although the estimates are still up for debate, the question remains: if it is possible to stabilize and mitigate the aging process at some point in life, why wouldn't it be possible to do it at a younger age?
Evidence that indicates this is possible is abundant in nature. There are several species that show negligible aging, i.e. which do not present an increased risk of death (or hazard rate) with age. For example, some species of turtles live for decades and show no signs of senescence. The Greenland shark is yet another vertebrate of extreme longevity and can live more than 400 years. Even among closer species and with similar habits, the lifespan can vary greatly. The naked mole-rat is a rodent that lives up to 30 years and practically does not develop cancer, unlike other rats and rodents that live a maximum of 5 years. Some species, such as the hydra, are even considered "immortal", or "amortal", because they do not die from causes related to aging. Even in humans, there are cells that can be considered amortal, such as germline cells. In other words, nature offers us examples of how aging and lifespan can be controlled. Looking at these examples, understanding how individual's senescence rate is determined, and proposing strategies to delay aging are the goals of a growing field called biogerontology.