The limit of human longevity achieved? Certainly not!
In 1997, at the age of 122 years died Jeanne Calment. It was the longest-lived person in the history of mankind (at least among those whose death has been documented). But there will be others after it. According to a new study published in Science, people are not even close to getting to the maximum life span - if such a limit exists. Analyzing the mortality rate among 4,000 Italian centenarians aged 105 years and above, the researchers found that the risk of death - which increases with time throughout human life - suddenly decreases in very old. If you live up to 105 years, your chance of dying in a given year are 50/50.
If it is proven among other populations, mortality alignment - "Plateau of death" - would have enormous consequences.
"If there is a plateau mortality limit to human longevity is not," says Dr. Jean-Marie Robine, a demographer from the French Institute of Health and Medical Research, who was not involved in the study.
The Battle for age
Although scientists have long agreed that the risk of death has been steadily increasing in aging person until the age of 80 years, what happens next - the subject of fierce dispute between the two camps.
The first group believes that the duration of a person's life there is a limit. Back in 2016 Dr. Jan Vijay from the Albert Einstein College of Medicine in New York City began a heated debate when his team found that human life rests on the biological ceiling in about 115 years. In their study, the team turned to two international databases on life expectancy to determine the likelihood that an elderly person can die in a given year. The results seem clear: although the maximum term of life increased by about five years - up to 115 between 70-bit and 90-ies, the trend stopped in 1995. Despite the innovations in medicine, such as sanitation, antibiotics, vaccines, surgical techniques, people can not die later. Though centenarians-champions such as Kalman certainly meet Vidzha team came to the conclusion that the person likely to live to 125 years old is 1 to 10,000.
The results make sense. All animals have a natural life span of dogs, for example, will never live as long as there are people, regardless of diet, exercise or other health care procedures. Biology also requires a hard limit. With the aging of our DNA and proteins accumulate damage, transforming the organism of the molecular mechanism calibrated in the waste pile.
Even if age-related diseases do not kill, at some point, the body just goes into denial. Sverhdolgozhiteli, in particular, did not die from disease - Kalman, for example, died for unknown reasons - but still continue to die.
"Too many functions of the body fails," Vijay explained at the time. "The body can not live."
But sooner despair. Investigation Vidzha provoked fierce debate among scholars almost immediately, as soon as got into the Internet. Some have argued that his statistical methods were flawed. Others said that the findings are not based on sufficient evidence. A few months after the original publication Vidzha, five teams have expressed criticism of the official in a number of papers published in Nature.
"There is an alternative explanation," says Dr. Maarten Peter Rosing of the Center for Healthy Aging at the University of Copenhagen, who at the time was the co-author of one of the denials. "The maximum age of just increases over time, and what we see as a decline in life expectancy is actually a false conclusion based on a visual examination and statistics that can not be so regarded."
New research bursts into this firestorm with more and improved data set.
Human demographers are facing two major problems, studying the life expectancy. First, not many people live to old age, to collect enough statistics. Second, people tend to forget their age and self-reports may be corrupted.
"At that age becomes a problem to prove that the real age," explains Dr. Elisabetta Barbie from the University of Rome.
In order to ensure the quality of your data set, Barbie and her colleagues used a precious resource: the record of each Italian aged 105 years or older between 2009 and 2015. These individuals were certificates of birth and death, which allowed scientists to confirm the exact age of each, avoiding the problem of "exaggeration of age." Each of those who were alive at the time of the study, the researchers made the survival of the certificate.
This data set also allowed the team to keep track of each person for a few years, rather than grouping them by age intervals - a practice adopted in previous studies, which use the combined data sets. Tracking individual trajectories of survival - is the most important part of the demographics, especially in a relatively large sample of 4,000 people, about 450 of them - men.
"I think this is the best information we could get," says study author Kenneth Wachter.
The results showed that the death rate soars in 70-80 years and women live longer. But, in contrast to previous data sets, these Italian superdolgozhiteli clearly showed that the risk of dying is leveled to the plateau to the age of 105 years. The scientists also found that people who were born relatively late in the sample, have a lower mortality rate in the age of 105 years. Consequently, over time, the plateau decreases.
"If at the age of 105 years, the chances of survival are better, we will not come up against in any hard limit," says Wachter. Consequently, life expectancy is increasing.
"The results are very interesting and surprising," said Dr. Siegfried Hekimi, a biologist at McGill University in Montreal. Hekimi co-wrote one of the most critical jobs in 2017 in response to a study Vidzha. Now, this study provides the best evidence that mortality is reduced in a state of extreme old age.
The new study is not without its critics. Dr. Brandon Milholland, who participated in the determination of the 115-year limit, says that the new study was too limited and observed only a small fraction of the human population in the same geographic area. It remains to determine whether these results apply to the rest of humanity.
Why does death suddenly departs from the oldest?
The new study does not answer this question, but the authors have some ideas. One of them - natural selection. Some people may have genes that make them more vulnerable to disease than others. Such people may die long before they reach the age of 105 years and would retain the majority of the elderly.
Another option - perhaps more interesting - is that at some point reduction mechanisms of the body to compensate damage. Sverhdolgozhiteli can just enjoy the slow life at the molecular level of cells do not divide frequently and may have a lower metabolic rate, resulting in less damage.
We see this in the example of cancer, says study author James Vopel. "Cancer - a fairly common cause of death in 70, 80 or 90 years. But very few people die from cancer than 100 years old. " "The presence of such a plateau indicates that something holds the key to a bad outcome in a large age," says Wachter. We do not yet know which genetic effects are responsible for this inhibitory effect, but they are likely to occur at a young age - and their detection can be important for understanding aging and possible recovery.
The new study is unlikely to resolve the dispute in age, but if the conclusions will be proved with the help of larger data sets, it will open up an incredible opportunity to fight aging. Many experts believe that very old people are not amenable to medical treatment. But if the chance of death does not increase with age, at some point, then the interference with the use of drugs or calorie restriction can help, and the oldest.
In other words, we can prevent death. Perhaps, at any age.