President Barack Obama was sworn into office on January 20, 2009, at the age of 48.

President Barack Obama was sworn into office on January 20, 2009, at the age of 48.

At the press conference later this year, Mr. Obama looked noticeably older as he prepared to end his two terms.

Some dermatologists also affirm that he is the latest example of the rapid aging process in presidents due to work pressure.

When looking back at his time in office, he used the image of his gray hair to emphasize the weight of the responsibility he held.

`Right now, we are waging war under the authority approved by Congress 15 years ago,` he said in a speech on counterterrorism strategy.

At the press conference later this year, Mr. Obama looked noticeably older as he prepared to end his two terms.

Some dermatologists also affirm that he is the latest example of the rapid aging process in presidents due to work pressure.

When looking back at his time in office, he used the image of his gray hair to emphasize the weight of the responsibility he held.

`Right now, we are waging war under the authority approved by Congress 15 years ago,` he said in a speech on counterterrorism strategy.

Then President-elect George W. Bush called immediately after the 2000 election. Photo: Reuters

Then President-elect George W. Bush called immediately after the 2000 election. Photo: Reuters

Mr. Bush answered questions during the last press conference at the White House on January 12, 2009.

A study by experts from Harvard Medical School on presidential elections from 1700 onwards shows that leading a country can even lose several years of presidents’ lives.

Mr. Bush answered questions during the last press conference at the White House on January 12, 2009.

A study by experts from Harvard Medical School on presidential elections from 1700 onwards shows that leading a country can even lose several years of presidents’ lives.

Hillary Clinton whispered into the ear of her husband, Bill Clinton, at a dinner party a few days before he took office as US president in 1993. Photo: Reuters

Hillary Clinton whispered into the ear of her husband, Bill Clinton, at a dinner party a few days before he took office as US president in 1993. Photo: Reuters

Mr. Clinton gave a short speech as he prepared to end his term in October 2000.

Mr. Clinton gave a short speech as he prepared to end his term in October 2000.

Without glasses, 1988 US Vice President George H. W. Bush answered questions at the second debate between presidential candidates.

Without glasses, 1988 US Vice President George H. W. Bush answered questions at the second debate between presidential candidates.

In June 1992, Mr. Bush spoke to veterans at the Korean War Memorial in Washington wearing a pair of glasses.

In June 1992, Mr. Bush spoke to veterans at the Korean War Memorial in Washington wearing a pair of glasses.

President Ronald Reagan and first lady Nancy Reagan wave to supporters in Washington at the swearing-in ceremony in January 1981.

President Ronald Reagan and first lady Nancy Reagan wave to supporters in Washington at the swearing-in ceremony in January 1981.

Mr. Reagan returned to the capital after his last visit as president to Camp David in January 1989.

Mr. Reagan returned to the capital after his last visit as president to Camp David in January 1989.

Mr. Jimmy Carter walked out of a voting booth in Georgia on election day in November 1976.

Mr. Jimmy Carter walked out of a voting booth in Georgia on election day in November 1976.

Mr. Carter prepared for his farewell speech to the people in January 1981.

Mr. Carter prepared for his farewell speech to the people in January 1981.

President Richard Nixon smiled during a press conference at the White House, a few weeks after being sworn into office in 1969. Photo: AP

President Richard Nixon smiled during a press conference at the White House, a few weeks after being sworn into office in 1969. Photo: AP

Four years later, he gave his final speech to White House staff and cabinet members.

Four years later, he gave his final speech to White House staff and cabinet members.

President Lyndon Johnson declared a national day of mourning for his predecessor John F. Kennedy, who was assassinated shortly after taking office in 1963. Photo: AP

President Lyndon Johnson declared a national day of mourning for his predecessor John F. Kennedy, who was assassinated shortly after taking office in 1963. Photo: AP

After 5 years as president, Mr. Johnson does not look too old.

See more: Memorable moments during Obama’s 8 years in the White House

After 5 years as president, Mr. Johnson does not look too old.

See more: Memorable moments during Obama’s 8 years in the White House

Mr. Ngoc