In many countries around the world, people are living longer – but is there a pattern to this? That was the question posed by a team of demographers and it turns out, the answer is yes. Despite some differences in how it reaches this point, life expectancy is increasing, and with it, the longevity gap between males and females is getting smaller.

What David Atance of Universidad de Alcalá, Spain, and colleagues sought to find out was whether there were differences in the factors affecting longevity or mortality across countries. If so, they also wanted to determine whether those differences were becoming stronger, or if patterns were actually converging.

The team used both historical data from the United Nations Populations Division records and population projections for 194 countries spanning from 1990 to 2030 to conduct a statistical analysis of nine mortality indicators, including life expectancy at birth and the Gini index (a measure of inequality in lifespan).

The results revealed that in 1990 and 2010, countries could be clustered into five separate groups, resembling the continents, based on their mortality/longevity indicators. In the period between those years, countries sometimes swapped clusters, though the researchers attribute this to factors such as war, or unstable socioeconomic and political conditions.

However, all clusters were found to have something in common – life expectancy had increased, while the gap in mortality between males and females had shrunk. The team also identified a decrease in the disparities in longevity between groups of countries, suggesting that, overall, patterns of longevity are converging. 

When the same statistical model was applied to projections for 2030, these trends were the same. However, the researchers acknowledged that it cannot be said for certain what will happen in the evolution of longevity, seeing as estimates are based on past trends. 

“As a future line of research, it would be particularly interesting to review our mortality estimates and cluster configurations in 2030, when we will have reliable data. This future analysis would allow us to assess the degree of accuracy of our 2023 estimates,” the researchers write in the paper describing their findings.

One country that exemplifies the increase in longevity is the US, where the number of people aged 100 or over has been steadily increasing since 1950. If projections do happen to be correct, they line up with the current study’s findings; the number of American centenarians is set to quadruple over the next 30 years, and whilst 78 percent of the current bunch are women, that’s set to decrease by 10 percent by 2054.

The study is published in the journal PLoS One.