從豪宅到專機，享受諸多特權的美國總統們，也有著比常人更多的壓力和煩惱。按常理，他們應該衰老的更快。但是美國一項研究表明，總統們老得快但壽命長。美國伊利諾伊大學研究者奧利尚斯基主攻人類衰老學科，他有一套壽命預期模型。這一模型計入各種因素，包括生存環境、飲食、壓力、醫療狀況等，可預期或計算某一時期特定年齡人群的壽命，也可針對某一特定個體定制，單獨預期壽命。奧利尚斯基以美國歷史上的所有總統為研究對象。結果發現，自然死亡的34位美國總統平均年齡73歲，比模型預期的68歲長5年。其中，實際死亡年齡超過68歲的總統總計11人，平均壽命78歲。奧利尚斯基說，歷任總統時常面對高強度壓力，衰老速度肯定比同齡人要快。但他們受教育水平、特別是他們擔任總統后所獲得的醫療服務一般都高于同齡人平均水平，因此，總統衰老快但是壽命更長。

Obama's estimated life span is 79.3 years, according to Olshansky, but he adds that Obama will probably live longer than that because of his education, wealth and health care.

The American presidency comes with perks, from a very nice house to a handy jet at your disposal, but the job also comes with plenty of stress.

Enough stress to take years off your life? Maybe not, new research suggests.

The data showed that presidents who die of natural causes don't seem to lose years off their lives due to the effects of time spent in the White House. In fact, most of them managed to live longer than similar men of their era.

The findings don't prove definitively that stress of the presidency has no effect on the life span of presidents. It may still take years off their lives; the research doesn't compare them to men of similar wealth and position, such as members of Congress.

Still, "they did a lot better than one would have predicted, given the circumstances that they were in," said study author S. Jay Olshansky, a professor of public health at the University of Illinois at Chicago. "There's no evidence that they're dying earlier."

Olshansky also thinks he's shot down one assumption: that each year in the White House typically takes two years off a president's life. A recent news report about that assumption, prompted by photos that showed the aging of President Obama, led Olshansky to try and see if there was any truth to it.

He was skeptical because presidents share three traits that have been linked to longer life spans: wealth, education and access to health care. "They've scored the trifecta," he said.

Olshansky compared the life spans of presidents who died of natural causes to the life spans of men who were of the same age as the presidents when they were inaugurated. There was a hitch, however, because full American statistics from 1789-1899 weren't available; Olshansky compared presidential life spans in that era to statistics from France, where he thinks men would have lived about as long as in the United States.

Of the 34 who died of natural causes (all except Kennedy, McKinley, Lincoln and Garfield), 23 lived longer than the average man would have, based on their ages at inauguration. They would have lived longer than the average for other men of their era even if they'd somehow aged at twice the normal rate while serving as president.

Commenting on the report, Dr James Goodwin, director of the Sealy Center on Aging at the University of Texas Medical Branch, said the idea that presidents will be adversely affected by stress is "fundamentally flawed." Research in animals and some in people suggests that the most dangerous type of stress comes with helplessness, such as "when you're a middle manager and can't change the system," he explained.

"When you're more in charge, it isn't a bad stress," he said.

Goodwin added that presidents aren't like other people. "You're selecting for people with tremendous life force, incredibly energetic, emotionally active and positive people," he said. "They're politicians."

One idea for future research would be to study the losers of presidential elections, who would share many traits with the winners but never actually ended up in the White House, he said.

The research is published in the Dec 7 issue of the Journal of the American Medical Association.

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(Agencies)

（中國日報網英語點津?Rosy 編輯）