Cocktails of HIV drugs are helping patients live an average of 13 years long - as long as they can afford them.

Drugs help extend life - if you can afford them

The medication used to treat HIV is known as combination anti-retroviral therapy (Cart).

These advances have "transformed HIV from being a fatal disease into a long-term chronic condition", the study said.

But, the University of Bristol study found, life expectancy in HIV patients remains well short of the general population, and patients treated late in the course of their infection have worse life expectancy.

For the research, published in the journal The Lancet, a team of HIV experts compared changes in mortality and life expectancy among HIV-positive individuals treated with Cart.

The study said that "despite" these positive results, an HIV-positive person starting Cart treatment at the age of 20 will on average live another 43 years, to 63.

A 20-year-old HIV-negative person in a high-income country can expect to live to around 80, a difference of nearly 20 years.

The journal said the improvements in life expectancy and mortality were linked to the improvements during the first decade of Cart treatment.

"The results of this study indicate that people living with HIV in high-income countries can expect increasing positive health outcomes on Cart.

"The marked increase in life expectancy since 1996 is a testament to the gradual improvement and overall success of such treatment."

The study also revealed that patients who contracted HIV through infected needles used to inject drugs had a shorter life expectancy - 32.6 years - than the average of those from other groups - 44.7 years.

Women also have a slightly longer life expectancy than men - 44.2 years for women to 42.8 years for men - which may be due to women on average starting treatment earlier in the course of HIV infection.