Having HIV — or getting treatment for it — speeds up the aging process by about five years, on average, scientists report in a new study.
The findings, published in the journal Molecular Cell, fit with what doctors have seen in clinics: HIV-positive people tend to get hit earlier in life with age-related diseases, such as osteoporosis, heart disease and dementia.
But the study also opens up the possibility of addressing a broader question: How to measure a disease's impact on aging.
"We all know that some people appear to age faster than others," says Trey Ideker, a biologist at the University of California, San Diego, who co-led the study. "There are external signs of aging, like gray hair and wrinkles. But the inside of our bodies also show signs."
One of those signals is hidden in our genomes — not the genetic code itself but how the genome is decorated.
Before you're born, your DNA gets decorated with little tags, called methylation, which help turn genes on and off. As you age, some tags fall off. Others get added. By looking at the pattern of these tags, Ideker and his colleagues found they could estimate how fast a person is aging.
"And that measurement is better at predicting when someone will die than their chronological age — or the number of years they've been on Earth," Ideker says.
For instance, say you're 50 years old, but your DNA tags look like you're 55. Then your body is aging about 10 percent faster than the average 50-year-old's body. And you might want to get screened for age-related diseases five years earlier.
That's exactly what Ideker and his team found for men with HIV.
The team analyzed more than 25,000 DNA tags on the genomes of 137 HIV-positive men. The researchers then used the patterns in the tags to estimate each man's "biological age" compared to his chronological age.
On average, each man's DNA looked like he was about five years older than his actual age. And it didn't matter if he had had HIV for more than a decade or if he was only recently infected. The bump in biological age was about the same.
All the men in the study were taking antiretroviral drugs. So Ideker and his team couldn't tell whether the age advancement is linked to the HIV infection itself or the drugs used to treat it.
Still, though, Dr. Howard Fox at the University of Nebraska Medical Center hopes the findings will help promote a healthy lifestyle among people who are aging with HIV.
"People think, 'I'm taking my retroviral drugs so there's no need to worry about my health,' " says Fox, who co-led the current study with Ideker. "But HIV puts you at an increased risk for other diseases. Whatever you can do to slow down the aging process — exercise, eating right — will help to offset this."