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الجمعة، 22 أكتوبر، 2010

New York Times:Taking Early Retirement May Retire Memory, Too

Taking Early Retirement May Retire Memory, Too

The two economists call their paper “Mental Retirement,” and their argument has intrigued behavioral researchers. Data from the United States, England and 11 other European countries suggest that the earlier people retire, the more quickly their memories decline.
The implication, the economists and others say, is that there really seems to be something to the “use it or lose it” notion — if people want to preserve their memories and reasoning abilities, they may have to keep active.
“It’s incredibly interesting and exciting,” said Laura L. Carstensen, director of the Center on Longevity at Stanford University. “It suggests that work actually provides an important component of the environment that keeps people functioning optimally.”
While not everyone is convinced by the new analysis, published recently in The Journal of Economic Perspectives, a number of leading researchers say the study is, at least, a tantalizing bit of evidence for a hypothesis that is widely believed but surprisingly difficult to demonstrate.
Researchers repeatedly find that retired people as a group tend to do less well on cognitive tests than people who are still working. But, they note, that could be because people whose memories and thinking skills are declining may be more likely to retire than people whose cognitive skills remain sharp.
And research has failed to support the premise that mastering things like memory exercises, crossword puzzles and games like Sudoku carry over into real life, improving overall functioning.
“If you do crossword puzzles, you get better at crossword puzzles,” said Lisa Berkman, director of the Center for Population and Development Studies at Harvard. “If you do Sudoku, you get better at Sudoku. You get better at one narrow task. But you don’t get better at cognitive behavior in life.”
The study was possible, explains one of its authors, Robert Willis, a professor of economics at the University of Michigan, because the National Institute on Aging began a large study in the United States nearly 20 years ago. Called the Health and Retirement Study, it surveys more than 22,000 Americans over age 50 every two years, and administers memory tests.
That led European countries to start their own surveys, using similar questions so the data would be comparable among countries. Now, Dr. Willis said, Japan and South Korea have begun administering the survey to their populations. China is planning to start doing a survey next year. And India and several countries in Latin America are starting preliminary work on their own surveys.
“This is a new approach that is only possible because of the development of comparable data sets around the world.” Dr. Willis said.
The memory test looks at how well people can recall a list of 10 nouns immediately and 10 minutes after they heard them. A perfect score is 20, meaning all 10 were recalled each time. Those tests were chosen for the surveys because memory generally declines with age, and this decline is associated with diminished ability to think and reason.
People in the United States did best, with an average score of 11. Those in Denmark and England were close behind, with scores just above 10. In Italy, the average score was around 7, in France it was 8, and in Spain it was a little more than 6.
Examining the data from the various countries, Dr. Willis and his colleague Susann Rohwedder, associate director of the RAND Center for the Study of Aging in Santa Monica, Calif., noticed that there are large differences in the ages at which people retire.
In the United States, England and Denmark, where people retire later, 65 to 70 percent of men were still working when they were in their early 60s. In France and Italy, the figure is 10 to 20 percent, and in Spain it is 38 percent.
Economic incentives produce the large differences in retirement age, Dr. Rohwedder and Dr. Willis report. Countries with earlier retirement ages have tax policies, pension, disability and other measures that encourage people to leave the work force at younger ages.
The researchers find a straight-line relationship between the percentage of people in a country who are working at age 60 to 64 and their performance on memory tests. The longer people in a country keep working, the better, as a group, they do on the tests when they are in their early 60s.

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