While their policies and defining moments may differ, there's one thing every president of the United States has had in common: aging. Or rather, dealing with the perception that holding one of the most stressful jobs on the planet speeds up the aging process, causing wrinkles, gray and thinning hairs to appear faster than if they hadn't held the nation's highest office.

CNN recently put together a video comparing how the presidency wore on aging presidents 42-44: Bill Clinton, George W. Bush and Barack Obama. The video compares a picture taken of each president during weeks one through 198 of their terms, and asks the slightly inane question: "Who does it best?"

Researchers have gone back and forth on the idea of what's behind seemingly fast aging presidents. Michael Roizen of Cleveland Clinic, a non-profit medical research center in Ohio, suggests presidents age two years for every average person's one year.

But longevity expert and University of Illinois, Chicago professor S. Jay Olshansky disagreed. If presidents aged faster than average, shouldn't they die sooner? Olshansky looked at the birth, inauguration and death dates of the 34 presidents who died of natural causes and found there was no evidence that they aged faster than the average person. In fact, two-thirds of the presidents surpassed the life expectancy in Roizen's theory and compared to men who were the same age they were when inaugurated, thanks to their higher education and socioeconomic standing. "They lived as long as American women do today,” Olshansky said.

So why do presidents seem to age right before our eyes? Well, because they are, Olshansky told the Wall Street Journal.

"If you were to take a picture of any person in his or her mid 50s or early 60s and come back four or eight years later, you’re likely to see more gray hairs and wrinkles, he says. It’s just that the president is so frequently photographed, we are more likely to see the changes. Importantly, 'we don’t die from gray hair and wrinkling skin,' notes Olshansky."

Quick Poll

Which president seemed to age the most during office?

VOTE

Loading Slideshow...
  • George W. Bush: Jan. 11, 2001:Nov. 5, 2008

    Presidents may enter the office bright-eyed, but they tend to leave with a few more wrinkles and a lot more gray hairs. Compare a younger President George W. Bush, left, before the economic crisis, before Iraq and before Sept. 11, 2001, to Bush in early November.

  • Bill Clinton, family leave bill signing: Nov. 11, 2000

    Scandal certainly takes a toll. Bill Clinton may have dallied with a younger woman, but that couldn't stop the aging process as he approached the end of his tenure, pictured here on the right.

  • Pres. George H. W. Bush

    Maybe serving a single term isn't so bad. The elder George H. W. Bush looked pretty much the same early in his presidency, left, as he did later.

  • Ronald Reagan: Kan. 1981 in L.A.: posing in D.C.

    Could it just be the Hollywood lighting? Ronald Reagan looked younger in a portrait taken in Los Angeles the month of his inauguration, left, than during his last months in office.

  • Jimmy Carter, Feb. 1977: Oct. 1, 1980

    Like the elder George Bush, Jimmy Carter only served for four years. It appeared to weigh heavily on him. That furrowed brow late in his term, right, couldn't have been good for his complexion.

  • Gerald Ford. inauguration: conceding in 1976

    Gerald Ford was the only U.S. president to never win an election, and is pictured here, on the left, at his inauguration. Is it a trick of the light, or did he really look a little beefier, and a little older, as he later conceded to Carter two years later?

  • Richard Nixon, Jan. 20, 1968: April 1974

    Watergate clearly took its toll on Richard Nixon. He looked quite different at his inauguration, left, than he did in the midst of the scandal, six years later.

  • Lyndon B. Johnson (1st photo - Nov. 29, 1963)

    Lyndon B. Johnson looks a little grayer and a little more wrinkled late in his administration, but he does appear to have lost a few pounds. Maybe there's a silver lining after all.

  • John F. Kennedy, 1961 and Jan. 24, 1963

    John F. Kennedy appears to have a fuller face at the start of his presidency, as seen in this 1961 on the left. The second photo was taken in January 1963, 10 months before his assassination.

  • Dwight D. Eisenhower, March 1, 1953 and Nov. 1, 1960

    There was no hair to lose for Dwight D. Eisenhower, as first seen in 1953, but his two terms in office aged the man, as evident in the photograph from 1960.

  • Harry Truman, 91/1945 and 1/1/1953

    Harry S Truman took office with the death of President Roosevelt in 1945, and he described his sudden ascent as feeling "like the moon, the stars and all the planets had fallen on me." All that pressure can wear on a man, as seen in an aged Truman in 1953, shortly before he left office.

  • Franklin D. Roosevelt, 1933 and Feb. 11, 1945

    Franklin D. Roosevelt president over the nation as it struggled with the Great Depression and World War II. He served in office for a record four terms. It's not surprise then that he aged so much in office, as seen in 1933 and 1945. (Sources: AP, Getty, the Washington Post)