Washington ? The most powerful man in the world turns 60 on Thursday, and he just can’t seem to stop talking about it. Barely a week has gone by this year that President Bush has not brought up his advancing age at least once.

“How you doing, sir?” a reporter asked Bush at a news conference a few hours after a middle-of-the-night return from a grueling sprint to Baghdad. “I’m doing all right, thank you,” the president replied. “A little jet lagged, as I’m sure you can imagine. Nearly 60.”

In his State of the Union address, the president referred to his upcoming birthday as “a personal crisis.” It was a laugh line – used to segue to a call for overhauling programs, such as Social Security and Medicare, soon strained by Bush’s baby boomer generation.

In fact, Bush is nearly always cracking wise when the topic of his age comes up. The humor, however, contains unmistakably wistful notes, revealing a president who is least somewhat pensive both about aging and his relevance after he leaves the White House in 31 months.

Bush’s “I’m getting old” preoccupation puts him in good company.

Cher, Bill Clinton, Dolly Parton, Donald Trump, Sylvester Stallone, Diane Keaton, Suzanne Somers, Reggie Jackson and Jimmy Buffet also are turning 60 in 2006. They are part of the first wave of the 78-million strong baby boomers to enter their senior years.

President Bush rides his mountain bike on the Laoshan Olympic Mountain Bike Course in Beijing in this Nov. 20, 2005, file photo. Bush will turn 60 on Thursday.

Karl Pillemer, a professor of human development at Cornell University, said the president’s musings are reflective of the group.

Boomers brought advances in the civil rights and women’s rights movements. But the generation also introduced America to what Pillemer called “the new narcissism.” And now, members of this group are presented with a slew of sometimes bewildering roles: seeing their children enter adulthood; contemplating grandparenthood; watching their parents age and die; retiring from work; and dealing with physical and intellectual limitations.

“For many boomers, turning 60 is a fairly significant shock,” Pillemer said. “The generation that believed it would be young forever, clearly will not. … The boomers are having a hard time with the existential reality of life not being one open-ended opportunity after another.”

Dr. J. Edward Hill, the immediate past president of the American Medical Assn. and a physician from Tupelo, Miss., has seen many patients display Bush’s chatty angst. But he said the president’s joshing around is one of the healthiest approaches.

“When you worry about something, you talk about it,” he said. “The stints of humor are critically important.”

Ten other presidents have turned 60 in office. Dwight Eisenhower had his 70th birthday in the White House, as did Ronald Reagan. Seven others turned 50, including Clinton.