The slow down before the mid-century will then increase again, according to the study made at Stony Brook University and the World Population Program at the International Institute for Applied Systems Analysis in Austria.
The research findings are published in this week's online edition of the journal Nature.
The changes in longevity is based on the speed of population aging which, for example, assumes that a 60-year-old person in 1900 was as old as a 60-year-old person in 2000, Stony Brook said in a press statement.
"The speed of aging is crucial to understand because it is during the period of the fastest change when adjustments will be the most difficult," said lead author Warren Sanderson, professor and co-chairman of the Department of Economics at Stonybrook.
"Policy-makers will need to know ahead of time when peak aging will occur so they can have those adjustments in place, especially those dealing with the financing of pensions and healthcare for the elderly," he said.
