Over the past century, the human lifespan has been steadily increasing in large part due to advances in science, medicine and social conditions. In addition to longer average lifespans, the maximum age at death of the longest-living people also rose steadily throughout the 20th century, leaving many to speculate that human longevity may not have an upper limit.
However, despite the remarkable strides made over the last 100 years, a new study suggests that this upward trend in longevity has slowed down in recent years and that our lifespan may have already hit its natural limit.
The authors of the analysis—published earlier this month in the journal Nature—say their research shows that although more people reach old age each year, the ceiling for human lifespan appears to be stuck at around 115 years.
The researchers further contend their data indicates that even if we continue to cure diseases that affect people in old age, no one is likely to significantly outlive the oldest human on record, Frenchwoman Jeanne Louise Calment, who died in 1997 at the age of 122-years-old.
“The chances are very high that we [have] really reached our maximum allotted lifespan for the first time,” said Jan Vijg, senior co-author of the research from the Albert Einstein College of Medicine in New York.
This is a stark contrast to previous figures and predictions that have claimed that the first person to reach 1,000 years old is likely to be alive today.
But this latest study suggests that is highly unlikely. “Demographers as well as biologists have [long] contended there is no reason to think that the ongoing increase in maximum lifespan will end soon. But our data strongly suggest that it has already been attained and that this happened in the 1990s,” Vijg said in a statement.
What the data shows
For their study, Vijg and his team analyzed records from numerous international mortality databases from over 40 countries. The data showed a steady increase of life expectancy since the year 1900, which Vijg contributes to a number of factors, including advances in childbirth and maternity care, clean water, the development of antibiotics and vaccines and other health measures.
However, while the proportion of people surviving to old age—defined as 70 and older—has risen since 1900, the rate of improvements in survival differ greatly between varying levels of old age. For example, large gains are seen for ages 70 and up, but for ages 100 and over, the rate of improvement drops rapidly.
“The data shows that we’re not very successful at keeping people alive over the age 100, and that suggests that there may be a hard limit to human lifespan,” Vijg told CBS News.
Furthermore, data analysis indicates the ages shows the greatest rate of survival improvement have not changed since 1980, further suggesting the possibility of a limit on human life.
The research team also examined the death rates of “supercentenarians” (people 110 years or older) from the U.S., France, Japan, and Britain—four countries with the highest number of supercentenarians.
The data showed that the maximum age increased rapidly between the 1970s and early 1990s, rising by around 0.15 years every year. But in the mid-to-late 90s, a plateau was reached, with the yearly maximum reported age at death in this group plateauing around 115 years in 1995. The authors note that this is around the same time that Calment died.
The researchers’ model concludes that the maximum human life span reported most years is just short of 115, on average, though there will be occasional outliers like Calment. They also predict that the likelihood of a person exceeding age 125 in any given year is less than 1 in 10,000. Furthermore, based on the statistical trends, the authors argue that those who reach age 100 today do not have a longer life expectancy than individuals who reached the same age decades ago in the 1980s.
Why a limit?
Vijg and his team believe that the apparent limits on human life is not necessarily set by the diseases that kill us when we’re old, but is rather an inadvertent byproduct of a range of genetic processes that control our body’s growth, development and reproductive capabilities. As we age, our bodies are forced to change and grow in order to become able to reproduce. But along the way, these physical changes set in motion a process that has a natural endpoint.
“The idea is that every species has particular longevity assurance systems to keep them healthy at least until their reproductive age and then slowly it declines,” Vijg said. “At the end of the day, the body is overwhelmed by stress, damage, molecular errors and so on, and these defense systems are only good enough to protect you for only a given amount of time.”
However, Vijg point out that although the data “strongly suggest that human lifespan has a natural limit,” it doesn’t mean humanity could never find a way to break that limit. “The take-home lesson from what we found is that the human species most likely has a maximum life span of about 115 and we cannot break through that ceiling, at least not as far as we now know,” Vijg added.
The results may sound straightforward, but lifespan is still a widely debated subject in the scientific community.
Biomedical gerontologist Aubrey de Grey, who has famously argued that the first human to live to be 1,000 is already alive today, still sees age as nothing more than a disease to be cured — and a manageable one at that. “The result in this paper is absolutely correct, but it says nothing about the potential of future medicine, only the performance of today’s and yesterday’s medicine,” Grey told Nature.