The burden of ageing populations in industrialised societies is less than expected because the health of the elderly has improved, according to study in the journal Science.
Study authors propose new tools to help policy makers better estimate the economic costs of ageing, and to determine a more appropriate retirement age.
As wealthy countries face an unprecedented rise in the number of people over 65, researchers have developed a new aging indicator taking into account different degrees of disability and longevity.
Current determinations are based largely on United Nations ageing forecasts based on the proportion of the population age 65 and older, and the "old age dependency ratio" (OADR), which considers the number of people dependent on others when they reach age 65.
May have misleading results
"Those measures are based on fixed chronological ages, and this can generate misleading results," said researcher Warren Sanderson, from Austria's International Institute for Applied Systems Analysis (IIASA) and Stony Brook University (SBU) in the United States.
"When using indicators that assume fixed chronological ages, it's assumed that there will be no progress in factors such as remaining life expectancies and in disability rates. But many age-specific characteristics have not remained fixed and are not expected to remain constant in the future," Sanderson said.
An increasing number of people 65 and older do not need care and sometimes are caregivers themselves, the researchers said.
When ageing is measured based on a ratio of those who need care to those who can deliver care, the speed of aging is reduced by four-fifths compared to the conventional old-age dependency ratio, the researchers said.
Populations aging slower
"If we apply new measures of ageing that take into account increasing life-spans and declining disability rates, then many populations are aging slower compared to what is predicted using conventional measures based purely on chronological age," said co-author Sergei Scherbov, from the IIASA and also Austria's Vienna Institute of Demography (VID).
The researchers analysed other measures, including one looking at the ratio of disabilities in adults over the age of 20 in a population.
In Britain, for example, while the old age dependency ratio is increasing, the disability ratio is remaining constant.
"Although the British population is getting older, it is also likely to be getting healthier, and these two effects offset one another," the study said.
New ways of measuring ageing that include both changes in longevity and accurate numbers about disability rates, "can help educate the public about the likely consequences of improvements in health and longevity," according to the authors. (Sapa, September 2010)