It is the biggest-ever assessment into the effectiveness of highly active antiretroviral therapy -- the triple cocktail of drugs that suppress, but do not eradicate, the human immunodeficiency virus (HIV).
Publishing on Friday in the British weekly medical journal The Lancet, researchers report on 14 ongoing studies into more than 33,000 HIV-infected people living in Europe, Canada and the United States.
These people started antiretrovirals in one of three phases -- from 1996-1999; from 2000-2002; and from 2003-2005.
From 1996 to 2005, 2,056 patients died, but mortality fell by around 40 percent in the course of this period. Life expectancy at the start was 36.1 years but rose to 49.4 years at the end.
"These advances have transformed HIV from being a fatal disease, which was the reality for patients before the advent of combination treatment, into a long-term chronic condition," says the paper.
The team is headed by Robert Hogg, a professor at Simon Fraser University in Vancouver, Canada.
The study found that people who were treated earlier after infection and had a higher number of CD4 immune cells at the start of the therapy had a better life expectancy.
Despite the greater overall survival chances, there remained a big gap in life expectancy between people on antiretrovirals and the general population, the authors found.
In a rich country, an HIV-positive person starting the drugs at the age of 20 will on average live another 43 years, to the age of 63, while a non-infected person will survive to around 80, according to this data.
The mortality figures culled in the study are not detailed enough to explain this discrepancy, the authors admit.
Nor -- given most people with HIV are under 50 - are there yet any figures to compare survival among older HIV-infected people compare with non-infected counterparts.
In high-income economies, a disproportionately high number of injecting drug users have HIV, where there is a higher risk of suicide or a fatal overdose.
Australian AIDS expert David Cooper at the University of South Wales, near Sydney, said that the study was a useful pointer to people with HIV as to how long they could expect to live if they had access to the antiretroviral lifeline.
Since AIDS emerged in 1981, the disease has claimed around 25 million lives and another 33 million are infected, some two-thirds of whom live in sub-Saharan Africa.