Researchers behind a new report argue that humans have already achieved their maximum possible lifespan. The investigators believe that the oldest people on record have hit the ceiling of longevity.
Since 1900s, the human lifespan has steadily increased as a result of improved healthcare and diet. In the United States and other countries, the average lifespan has gradually increased from around 47years in 1900 to around 79 years today. Since the 1970s, the age of the oldest people on earth has also risen. However, researchers believe that we have now touched the upper limits of maximum age.
Analyzing the Human Mortality Database, which collates information regarding mortality and population data from over 40 countries, researchers found that since 1900 each birth year a larger fraction of people survived beyond the age of 70. This pointed toward a steadily increasing average life expectancy.
However, when the team investigated survival improvements for people aged 100 and above from the start of the previous century, a different picture emerged. When studying this older cohort, they saw that gains in survival peaked at around the age of 100 and then dropped rapidly - irrespective of the year they were born.
To further understand this finding, the team looked at maximum reported age at death in the International Database on Longevity. Specifically, they looked at people who reached 110 or older, anywhere between 1968-2006 in the four countries with the largest numbers of people reaching these ages, namely the US, Japan, France, and the UK.
They found that the age at death for these super-centenarians increased swiftly from the 1970s to the 1990s. Then, in the mid-90s, they plateaued. Researchers put the average maximum human lifespan at 115 and they calculated the absolute maximum lifespan of a human to be 125 years.
The researchers conclude that further progress against infectious and chronic diseases may continue boosting average life expectancy, but not maximum lifespan. While it is conceivable that therapeutic breakthroughs might extend human longevity beyond the limits calculated, such advances would need to overwhelm the many genetic variants that appear to collectively determine the human lifespan. They suggest that perhaps resources spent on increasing lifespan should instead go to lengthening the duration of old age spent in good health.