Leading a nation may come with the attending worries and stress, as manifested by greying hairs and wrinkles on many Presidents and Prime Ministers, but it will not necessarily shorten one's life, according to a new study.

While heads of state enjoy immense quality of life, many assume that presiding over state matters chip away considerable number of years from a sitting President or Prime Minister, which will eventually catch up with them once they leave office and cut short their liveable years.

But basing on the research conducted by S. Jay Olshansky of the University of Illinois in Chicago, that notion was contradicted as stress hardly plays a role in accelerating the deaths of past United States president, who mostly passed away due to natural cause.

Olshansky noted too that stress has not been observed so far as the culprit in the untimely death of any incumbent president as he allowed that four actually died in office, no thanks to assassins' bullets.

He, however, conceded that aging seems to accelerate while living in the White House, with the present example seen on U.S. President Barack Obama, whose greying hair and multiplying facial linings have been observed by many. The same goes with his immediate predecessor, President George W. Bush.

"Just because they experience what would appear to be accelerated aging outwardly, doesn't mean they will die any sooner," the American demographer told Reuters.

In his study published recently by the Journal of the American Medical Association, Olshansky said that majority of past U.S. presidents actually lived long lives once they the rigorous routines of the presidency, with some even outliving their peers.

This pattern was observed from 23 out of the 34 American presidents who died of natural causes, with the study noting that the conclusion was arrived at by cutting down the men's expected life span by at least 8 years, the estimated amount of time that they supposedly lost while in office.

The incredible result, Olshansky said, can be attributed to three major factors - quality of life, health care access and better education.

"All of these presidents benefited from the trifecta of exceptional wealth, almost all were highly educated and all of them had access to medical care," Olshansky's report offered.

To begin with, most of the past U.S. presidents were beyond the age of 55 when assumed office, which means they were mostly past the dangerous phase of battling various illnesses and infections, and they survived.

"They have survived the early perilous decades of life ... that's not trivial," Olshansky pointed out.

Overall, most U.S presidents lived though an estimated lifespan of 67.8 years as shown by Olshansky's calculations, which also highlighted a baffling number showing that the first eight presidents of the then young republic actually lived much longer, at about 79.8 years.

The reason cannot be exactly explained by Olshansky, in the same way that he's puzzled why U.S. presidents sent to the White House by American voters between 1841 and 1923 lived shorter at 62.1 years.

It is unclear though if these presidents, who died relatively young, are less educated, enjoyed modest wealth or simply too weak to have survived the punishing hours of being president.