People who survive to age 65 living in a developed country can hope to live longer than their parents, according to a new study performed by researchers at Stanford University. These findings seem to push the envelope of human longevity, whose limits are yet to be reached.
“The data shows that we can expect longer lives and there’s no sign of a slowdown in this trend,” Shripad Tuljapurkar, a Stanford biologist and co-author of the new study, said in a statement. “There’s not a limit to life that we can see, so what we can say for sure is that it’s not close enough that we can see the effect.”
No evidence for an impending limit to human lifespan
Tuljapurkar and colleagues analyzed birth and mortality data for individuals aged 65 or older from 1960 to 2010. During this time, the average age of death for people older than 65 increased by three years every 25-year period -- the equivalent of a generation. This means that people can expect to live six years longer than their grandparents, on average.
This trend seems to have stood the test of time for the entire 50-year period and in all 20 countries where this sort of data was analyzed. Although there were some minor fluctuations due to medical breakthroughs, the rate of lifespan increase was steady for any given decade.
What set this study apart from other longevity research is the fact that the focus was on people over age 65, rather than targeting extreme cases like people who live a long time (i.e. over 100 years). By eliminating outliers, the researchers were better equipped to study longevity trends in an age range with many individuals.
These findings suggest that if there's such a thing as a limit to human lifespan, we've yet to reach it. Otherwise, the distribution of ages when people die should compress as they approach this limit -- but this isn't the case, as the authors reported in the Proceedings of the National Academy of Sciences.
What was truly surprising was that the shape of the distribution of average age of death did not change. Researchers thought that certain lifestyle factors such as wealth should increase the likelihood of a person living longer. But if that would have been the case, the distribution of data should have widened as the wealthy live past the average age of death. The shape of the data, however, remained consistent over the 50-year period.
In today's world, it seems, being rich doesn't help you that much to live longer -- at least, not if you're over 65. By this age, the average person has already overcome the main factors that could shorten life, including violence and early disease.
“But as someone who would like to be a one-percenter but is not, I’m certainly very happy to know that my odds of getting to live longer are just as good as the millionaire down the street,” said Tuljapurkar.