A study in the US has found people living with HIV are nearly 50% more likely to have a heart attack.

Researchers aren’t sure what explains the higher heart attack rate for those who are HIV positive, but they speculate it’s a combination of the effects of HIV infection and the antiretroviral drugs used to treat it.

“It’s a complicated picture,” said Matthew Freiberg, who led the study at the University of Pittsburgh School of Medicine in Pennsylvania. “We’re still trying to understand the mechanisms.”

The new study included more than 82,000 US veterans, almost all men.

About one-third of them were HIV positive.

During an average of almost six years, nearly 900 of the study participants had a heart attack, of which 176 were fatal.

The researchers found that veterans with HIV were consistently more likely to suffer a heart attack than their HIV negative counterparts.

After researchers took into account participants’ other heart risks – including high blood pressure, diabetes and drug and alcohol use – those with HIV were still 48% more likely to have a heart attack during the study period.

Last December, the US Centers for Disease Control reported that gay and bisexual men accounted for 63% of all new HIV infections in 2010 while representing 2% of the US population.