London, April 16 (IANS): Faster increases in life expectancy do not necessarily produce faster population ageing, according to a new research.

This counter-intuitive finding was the result of applying new measures of aging developed at the International Institute For Applied Systems Analysis (IIASA), Austria, to future population projections for Europe up to the year 2050.

"Age can be measured as the time already lived or it can be adjusted taking into account the time left to live.

"If you don't consider people old just because they reached age 65 but instead take into account how long they have left to live, then the faster the increase in life expectancy, the less aging is actually going on," said Sergei Scherbov, who led the study.

Traditional measures of age simply categorize people as "old" at a specific age, often 65.

"What we think of as old has changed over time, and it will need to continue changing in the future as people live longer, healthier lives," Scherbov said.

"Someone who is 60 years old today, I would argue is middle aged. 200 years ago, a 60-year-old would be a very old person," Scherbov explained.

In the new study the researchers compared the proportion of the population that was categorised as "old" using the conventional measure that assumes that people become "old" at age 65 and the proportion based on their new measure of age, which incorporates changes in life expectancy.

The study looked at three scenarios for future population aging in Europe, using three different rates of increase for life expectancy -- from no increase to an increase of about 1.4 years per decade.

The results showed that, as expected, faster increase in life expectancy leads to faster population aging when people are categorised as "old" at age 65 regardless of time or place.

But surprisingly, they lead to slower population aging when the new measures of age are used.

The findings were published in the journal PLOS ONE.