WASHINGTON - AIDS is graying: By the end of the decade, the government estimates, more than half of Americans living with HIV will be older than 50. Even in developing countries, more people with the AIDS virus are surviving to middle age and beyond.

That's good news -- but it's also a challenge. There's growing evidence that people who have spent decades battling the virus may be aging prematurely. At the International AIDS Conference in Washington, numerous studies are examining how heart disease, thinning bones and a list of other health problems typically seen in the senior years seem to hit many people with HIV when they're in their 50s.

"I'm 54, but I feel older," said Carolyn Massey of Laurel, Md., who has lived with HIV for nearly 20 years. "When I hear young people talk about, 'Well you get HIV and you take your drugs and you'll be all right' -- that's just not the truth. This is a lifelong thing we're talking about, and it unfolds every day on you."

The graying isn't just because people like Massey are surviving longer. Some of it comes from older adults being newly diagnosed, a trend U.S. health officials say is small but slowly growing. Yes, grandparents still have sex -- and that's an age group missed by all those hip safe-sex messages aimed at teens and 20-somethings.

"They let down their guard," is how Dr. Kevin Fenton of the Centers for Disease Control and Prevention puts it.

Already, a third of the nearly 1.2 million Americans living with HIV are older than 50, and by 2020 half will be, Fenton said at one of numerous sessions on aging at the world's largest AIDS meeting. People 50 or older accounted for 17 percent of new HIV diagnoses in 2009, according to the CDC's latest data. That's up from 13 percent in 2001.

'50 is not old'

There aren't as good counts in poor regions of the world, where access to life-saving medications came years later than in developed countries.

But even in hard-hit sub-Saharan Africa, home to most of world's HIV-infected population, studies suggest 3 million people living with HIV are 50-plus, said Dr. Joel Negin of the University of Sydney in Australia. By 2040, he said, that could reach 9 million.

As Negin pointedly told the conference, "50 is not old." But for years, world health authorities didn't even measure HIV in people beyond age 49.

Today, people who are diagnosed and treated early can expect a near-normal life-span, said Dr. Anthony Fauci, infectious disease chief at the National Institutes of Health.

The new focus is on what these pioneering survivors can expect as they reach their 50s, 60s and beyond. They're now getting chronic illnesses such as heart disease, diabetes, kidney disease and osteoporosis -- some of the common ailments when anyone gets old. But studies suggest people with HIV may be at higher risk for some of those illnesses, or get them earlier than usual.

Perhaps the strongest evidence links HIV and an increased risk of heart disease. Some medications raise that risk. But in research published for the AIDS meeting, scientists at Massachusetts General Hospital uncovered another reason.

Risk for clots

They scanned the arteries of people with and without HIV, and found the HIV patients had more inflammation inside their arteries, putting them at risk for the kind of clots that trigger heart attacks. That's even though the HIV patients had their virus well-controlled and weren't that old -- their average age was 52, the researchers reported in the Journal of the American Medical Association.