Sanderson Writes About Aging in Science Magazine

Warren Sanderson

Warren Sanderson

Indicators of aging based only on chronological age are misleading and need to be adjusted to take into account advances in health and life expectancy, as reported in the September 10, 2010, issue of Science by Warren Sanderson, Professor in Stony Brook’s Department of Economics, and Sergei Scherbov, Vienna Institute of Demography (Austrian Academy of Sciences). Both are affiliated with the International Institute for Applied Systems Analysis in Laxenburg, Austria.

The article, “Remeasuring Aging,” calls for the adoption of the adult disability dependency ratio, which measures aging based on the ratio of those who need care to those who can give care. According to the study, the policy dialog on aging has been based on misleading information.

“Most of our information about aging comes from indicators published by the United Nations and statistical agencies,” said Sanderson. “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.”

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 “But this measure is now out of date, because people live longer and someone at age 65 is not an old person anymore,” the authors write.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

The authors write that 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.”

In the Science article, 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. Their 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.

The article is the latest in a series on aging by the authors that began with a 2005 Nature article that provided new measures of aging that take life expectancy change into account. “The first step is we redefined the concept of age because most people, when you ask how old they are, they’ll tell you how many birthdays they had,” Sanderson said. “We thought a better way to think of this is how many birthdays you have in your future. That’s what your life expectancy is. It’s like adjusting economic data for inflation.”

The authors then used that concept to create new aging measures for all countries of the world from 1955 and onward to 2045 based on the U.N. population forecasts. With the Science article, they go one step further and also take disability into account with the ADDR.

“It makes a big difference. There’s a lot of panic about aging,” Sanderson said of the ADDR. “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. The reasons why policy-makers have not used measures of aging like the ADDR that are adjusted for changes in disability rates are the lack of comparable data and the lack of an appropriate methodology. In the Science paper Sanderson and Scherbov use internationally harmonized data and develop a computer model that provides disability-based forecasts for high-income OECD countries.

“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.”

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