Former US President George H. W. Bush, 90, In Hospital

Former US president George H.W. Bush attends a game between the Cincinnati Bengals and Houston Texans at NRG Stadium on November 23, 2014 in Houston, Texas ©Bob Levey (Getty Images/AFP)

Former US president George H. W. Bush, 90, has been admitted to a Texas hospital suffering shortness of breath, a family spokesman said. "President Bush was taken by ambulance to the Houston Methodist Hospital as a precaution after experiencing a shortness of breath earlier this evening," his spokesman Jim McGrath said.

AFP reports "The former president, age 90, will be held for observation, again as a precaution."

The 41st US president and the oldest of the four living former US presidents, Bush has seemed frail in recent public appearances, and is often seen in a wheelchair.

He was well enough, however, to celebrate his 90th birthday last June, to make an assisted parachute jump out of a helicopter near his family retreat in Kennebunkport, Maine.

That tandem skydive jump was Bush's eighth, with the first on September 2, 1944 ― when he was shot down over the Pacific island Chi Chi Jima as a pilot in World War II.

Bush was previously treated at Houston Methodist in November 2012 for bronchitis, and ended up spending nearly two months as a patient there.

The former president's wife, Barbara Bush, nearly one year ago was admitted to the same Houston hospital where he is being treated.

Suffering from pneumonia, the former first lady was released from the hospital in January of this year.

A moderate Republican, George H. W. Bush was in the White House from 1989 to 1993 and sent US forces into Iraq in the first Gulf war after Saddam Hussein's forces invaded Kuwait.

The Massachusetts-born son of a senator, Bush is the patriarch of one of America's most prominent political dynasties. Prior to being elected president, he served two terms as vice president to Republican icon Ronald Reagan. During his long and varied career in public service, Bush also served as a US congressman, Washington's UN ambassador, US liason to China, and director of the Central Intelligence Agency. The decorated World War II aviator, who has earned widespread praise for his "Points of Light" voluntarism program, in private life made a fortune as a Texas oilman.

Bush is father to six children, including his eldest, the 43rd US president, George W. Bush, who earlier this year wrote what he described as a "personal biography" of his father that arrived in book stores just last month.

Another son, Jeb, just last week announced that he was laying the foundation for a 2016 White House bid.

In 2011, President Barack Obama awarded the senior Bush the Presidential Medal of Freedom, the highest US civilian honour.

Obama praised Bush's "humility and decency" and praised his diplomatic and foreign policy acumen in helping during his presidency to bring about an end to the Cold War without firing a shot.