In watching Marc Forster's new action drama "World War Z," it's hard not to be struck by how well Brad Pitt is aging.

Yes, there's the slightest of silver highlighting his long locks, and the added distinction those little lines are etching on his face, and that his body somehow defies the gravitational pull — but they're not the reason for my fascination. It's the ironic way the zombie thriller — a cleverly high-minded horror hoot — shows how carefully the actor is working his way through the treacherous terrain of the middle-aged movie star.

I realize it may qualify as heresy to pull the spotlight off actresses even for a moment. They've had to deal with the aging issue forever. Feminist enlightenment hasn't softened the realities of working in front of the camera, and the world at large has hardly eased its focus on the whole youth-equals-beauty mythology.

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Which may be why we have overlooked, or underestimated, the pressures aging puts on male stars. Right now, we have an impressive generation of major male stars just getting into the thick of it — Leonardo DiCaprio, Robert Downey Jr., Matt Damon, Will Smith, Mark Wahlberg, Ben Affleck and Matthew McConaughey among the most prominent. All are in their 40s but DiCaprio, who is nearly there, 39 in November. At the moment, the 50s belong to Denzel Washington, George Clooney and (if you can believe it) Johnny Depp.

They can learn from their elders (if not always betters). Some major marquee names have struggled mightily — Tom Cruise is Exhibit One. Cruise turns 51 in July, looks more like 41, yet you can feel the age unsettling, rather than enriching, his work. Director Michael Mann's "Collateral" in 2004 was the actor's last great film. In the years since, there have been some middling "Mission Impossibles." But the romantic action of "Knight and Day" was embarrassing. His cartoony sendup of a Hollywood producer in "Tropic Thunder" and his raging, aging rock star in "Rock of Ages" wobble on that thin line between laughing "with" and "at."

In this year's "Oblivion," the actor was the best thing about a B-movie, not reassuring. And never has the star looked more vulnerable, and not in a good way, than shirtless and posturing in last year's disastrous "Jack Reacher."

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DiCaprio in contrast, who like Cruise found success early, seems eager to take on characters that challenge even if, at times, that means an ancillary role. His smarmy, sadistic Southern bigot in "Django Unchained," was about as unlikable as any the actor has every played — and about as well drawn. Even in movies that haven't quite measured up — like "The Great Gatsby" — DiCaprio has, an actor of real solidity.

It is far easier in Hollywood, as elsewhere in life, to make the obvious but wrong choice. I'm sure "Pink Panther 2" looked good to Steve Martin on paper.

So what is to be done as the years tick by?

For the bible on how to do it right, there is no place else to start but with Clint Eastwood, who at 83 is turning out to be the best closer in Hollywood history. He keeps making great movies — directing, starring and collecting awards. A screen version of "Jersey Boys" is rumored, so apparently Eastwood's ambition — and energy — isn't dimming.

Robert Redford is another. He hasn't had Eastwood's consistent success behind the camera since the Oscar for his 1980 directing debut, "Ordinary People." But like his brilliant "Quiz Show" in 1994, the actor-director commits to projects he loves and stories he believes are important to tell. Not a Focker in the bunch. About to turn 77, his acting is getting a serious second wind too in J.C. Chandor's new film, "All Is Lost." The role was a risk, Redford goes solo, alone in a boat with nothing but his intellect and the elements. The camera — notably — in someone else's hands.

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Whether by choice or circumstance, Warren Beatty, 76, hasn't starred in a film since the 2001 bomb "Town & Country." It may be nothing more than adopting the Jack Nicholson approach — leave the work behind and spend the days playing elder statesman. After a series of great performances, "About Schmidt" in 2002 when he was 65 and 2006's "The Departed" when he was 69, the 76-year-old Nicholson has drifted into the forgettable.

For Michael Douglas, 68, the right role was on television. His recent glittery turn as Liberace in "Behind the Candelabra" was his best performance in years. It's not so much TV but surprising us. Tom Hanks, most memorable in the last 15 years for giving voice to "Toy Story's" Woody, tried out Broadway this year — "Lucky Guy" got him a Tony nod. Bill Murray completely changed his acting persona at 53 with "Lost in Translation." Suddenly the funny goof was introspective, edgy in a new way.

But that sort of sea change is rare. Douglas is up next in "Last Vegas," an old-boys buddy comedy with Robert De Niro, 69, and Morgan Freeman, 76. Are old guy buddy comedies becoming Hollywood's version of retirement living? Nicholson had a room with a view alongside Freeman in 2007's "The Bucket List." Last year, Al Pacino, 73, Alan Arkin, 79, and Christopher Walken, 70, got together as aging mobsters for "Stand Up Guys."

Sadly, the book on what not to do is being written by De Niro. One of our greatest working actors has lost himself in crummy, mindless comedy. I honestly believe the Oscar nod for "Silver Linings Playbook's" crusty dad was a part of the academy's positive reinforcement program so he wouldn't do another Fockers film. Because if you look closely, the distance between the dads is mostly the pedigree of the movie.

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I'm not arguing against De Niro in comedy. He can be terrific as he was in "Midnight Run" and "The King of Comedy." And getting work isn't his problem either — the actor has five films due this year. I guess the good news is that 2013 started with arguably the worst film of De Niro's career, "Big Wedding," so it has to be uphill from here, right?