An international scientific team conducted a survey among aging researchers – participants of a conference on biological aging and found that there was no unified or even predominant opinion on the definitions of aging and rejuvenation, as well as the most fundamental related questions. The report on the work was published in the journal PNAS Nexus.
Progress in Aging Research
In recent decades, significant progress has been made in aging research. Through various genetic, pharmacological, and dietary interventions, scientists have been able to significantly extend the lifespan of all major model organisms—from yeast and roundworms to rats and monkeys. However, convincing data on the causes and mechanisms of aging have still not been obtained, and no effective methods have been found to slow down or reverse aging in humans. Even definitions of aging in the scientific literature vary widely and are not always compatible with one another.
Vadim Gladyshev, the chair of the 2022 Systems Aging GRC conference on aging at Harvard Medical School, and his colleagues conducted a survey among the conference attendees. It included fundamental questions about aging, such as: what is the definition of this phenomenon, what are its causes, when does it begin, what is rejuvenation, and similar questions. A total of 103 attendees responded, including 29.8% professors, 25% postdocs, 22.1% graduate students, 13.5% industry specialists, and 9.6% from other categories. 
Aging researchers: Diverse Opinions on the Definition of Aging
Disagreements emerged even in defining aging. Analysis of verbal descriptions revealed 10 clusters of responses. Most often (about 30%), definitions referred to the loss of function over time, followed by the accumulation of damage and other harmful changes, as well as a multifactorial process of changes over time. Some participants based their answers on the phenotypic aspect of the process, others on potential causes, some on outcomes, and some on natural programs.
When asked what causes aging, about 30% of respondents pointed to damage and other harmful changes, while the remaining responses were distributed across categories such as dysregulation, unreliability of biological systems, molecular and systemic factors, evolutionary limitations, reduced repair, molecular and cellular drift, and natural programs. About 15% gave simple responses, and roughly the same number of respondents did not provide a clear answer, with a few admitting they didn’t know.
Similar diverse answers were given to the question about defining rejuvenation, including the reduction of cumulative damage, the acquisition of functions (though this opinion was expressed half as often as the definition of aging as loss of function), return to a youthful state, and others. There was also no agreement on what the most important unanswered question in aging research is, as it defines the direction of future studies. Regarding the age at which human aging begins, the most popular answers, in decreasing order, were: 20 years, gastrulation, conception, gametogenesis, 25 years, birth, 13 years, and 9 years; no one selected the “30 years” option.
Lack of Consensus: A Barrier to Progress
There was also no consensus between aging researchers on statements such as “aging is a disease,” “life expectancy in developed countries will increase by 10 or more years over the next 20 years,” and “when a person quits smoking, biomarkers of aging decrease—they have rejuvenated.” When asked if it is essential for the field to reach a consensus on the definition of aging, more than half of respondents answered affirmatively, but the number of those disagreeing or indifferent was not much smaller.
Thus, different researchers imply different events in the more or less accepted sequence of “damage causes functional decline, which causes age-related diseases, leading to death.” According to the authors of the study, this lack of agreement may represent a critical obstacle to developing the most effective strategies for addressing aging.
