STONY BROOK (US)—Chronological age is no longer the only factor when determining indicators of aging, according to a new study, which says advances in health and life expectancy also need to be taken into account.

Researchers calling for the adoption of an adult disability dependency ratio, which measures aging based on the ratio of those who need care to those who can give care, say the dialog to date has been based on misleading information.

“Most of our information about aging comes from indicators published by the United Nations and statistical agencies,” says Warren Sanderson, professor of economics at Stony Brook University.

“These indicators, which are used worldwide to determine health care and retirement costs, are based on chronological age and in many instances consider people as being old when they reach age 65 or even earlier.”

Details appear in the Sept. 10 issue of Science.

“With advances in health and life expectancy, measuring population aging presents a problem to demographers because the meaning of the number of years lived has changed,” the study says.

“In Western Europe in 1800, for example, less than 25 percent of males would survive to age 60, while today more than 90 percent of them do. A 60-year old man in Western Europe today has around the same remaining life expectancy as a 43-year-old man in 1800.  Today, a person who is 60 is considered middle-aged; in 1800, that 60-year-old was elderly. ”

Traditionally the old-age dependency ratio, OADR, (the number of people above age 65+ to people in working ages) was used to assess the burden to the society of supporting elderly people.

The increase of old age-dependency ratio was considered to reflect the growing burden on pension systems because of aging.

“But this measure is now out of date, because people live longer and someone at age 65 is not an old person anymore,” the study says.

“In the U.S., the normal pension age is now 66, is scheduled to rise to 67, and is likely to be increased further as a means to keep the Social Security system solvent.  Current legislation has normal pension ages rising in Germany, England, and other countries.  As normal pension ages rise, the old-age dependency ratio provides a more and more biased indicator of the burden of aging on pension systems.”

The same sort of bias occurs if policy-makers were to use the old-age dependency ratio as an indicator of the burden of aging on health care costs.  Most health care costs occur in the last few years of life and these years happen at ever later ages as life expectancies increase.

One area in which this rethinking is crucial is in measuring the burden of disability. “The traditional measure of old age dependency counts everyone 65+ years old as being a dependent on those in the working ages.

However, many people over the age of 65 are not disabled and in the need of the care of others, but, on the contrary, are capable of providing care to others.  On the other hand, some people below the age of 65 are disabled and in the need of care.”

The authors provide a new dependency measure they developed called the adult disability dependency ratio (ADDR), based on disabilities that reflect the relationship between those who need care and those who are capable of giving it.

The study shows that when aging is measured based on this ratio, the speed of aging is reduced by four-fifths compared to the conventional old-age dependency ratio.

“It makes a big difference. There’s a lot of panic about aging,” Sanderson says “They say ‘It’s going happen so fast and cause troubles and difficulties.’ I think when you say there are many ways to look at aging, many of these things don’t look as bad. We’re hoping this will start a new dialog based on better science.”

One reason why policy-makers have kept on using out of date measures that do not take life expectancy changes into account is that there used to be no simple alternative to the UN measures.

“Policy-makers now have a wider variety of aging measures available to them,” the study says  “When health and longevity are taken into account, measures of aging increase much less rapidly than they do when the implicit assumption is made that all improvements in health and longevity will suddenly come to a halt.

“Population aging will certainly be the source of many challenges in coming decades. But there is no reason to exaggerate those challenges through mismeasurement. We will be able to address those problems better with a larger array of measures of aging, using those that are appropriate to the task at hand.”

Sergei Scherbov of the Vienna Institute of Demography (Austrian Academy of Sciences) contributed to the study.

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