The human lifespan is increasing by approximately three years every generation – a trend likely to continue, a Stanford study has found. Researchers analysed life expectancy data from the past 50 years and found that people who survive to age 65 are continuing to live longer than their parents. Previous research has suggested that humans were approaching the limit to their longevity.
“The data shows that we can expect longer lives and there’s no sign of a slowdown in this trend,” said Shripad Tuljapurkar, a professor at Stanford University in the US. “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,” he said. The study, published in the journal PNAS, looked at birth and death data for people above age 65 from 1960-2010.
The researchers found that the average age of death in those who live to be older than 65 increased by three years in every 25-year period, which means that people can expect to live about six years longer than their grandparents, on average. The trend continued at a relatively stable pace over the entire 50-year period and in all 20 countries that they analysed. Factors like medical breakthroughs caused minor fluctuations in how quickly lifespans increased, but these variations averaged out over time.
The increase in lifespan during any given decade was very similar. Most longevity studies look at the outliers, the people who live longer than everyone else. The data get fuzzy, however, because so few people live that long, researchers said. They instead looked only at people over age 65, an age range with a large number of individuals.
According to the researchers, if we were about to hit a limit to human lifespans, the distribution of ages when people die should compress as they approach the limit. However, the researchers did not see that pattern in the data. The wave continued to move forward.