HIV-positive people in the world's rich countries now live nearly as long as those who don't carry the AIDS-causing virus, as drugs have cut the overall death rate in half, researchers said Friday.

Anti-retroviral treatment (ART) has cut the death rate from about 18 per 1,000 people between 1999 and 2001 to nine per 1,000 per year in 2009-2011, according to data from 200 clinics in Europe, the United States and Australia.

"These findings provide further evidence of the substantial net benefits of ART," said a study published in The Lancet medical journal.

"With the advent of effective anti-retroviral treatment, the life expectancy for people with HIV is now approaching that seen in the general population."

Developed in the mid-1990s, ART drug combinations do not kill the Human Immunodeficiency Virus (HIV), but slow its development into full-blown AIDS.

Before the advent of ARTs, which have to be taken for life, people who contracted the virus generally died after a few years, mainly from opportunistic infections and cancers taking advantage of the lowered immune defences.

The study of 50,000 HIV-positive adults found that complications of AIDS, the final immune-compromised stage of infection, were still the most common death cause, at 29 percent.

This was followed by non-AIDS cancers -- mainly lung cancer -- at 15 percent, liver disease with 13 percent and cardiovascular disease with 11 percent.

A decline in deaths among HIV-positive people from liver and cardiovascular disease may be due to generally healthier lifestyles -- less smoking and drinking, or the use of less toxic ARTs, said the study.

The reasons for a slight increase in non-AIDS cancers, however, were unclear.

"It is very encouraging that death rates are continuing to decrease among HIV-positive people. It shows how effective anti-retroviral treatment has been and continues to be," study author Colette Smith of the University College London told AFP by email.

"However, we must not be complacent. Disappointingly, we found AIDS was still the most common cause of death. We must make every effort to ensure that HIV-positive people are able to keep taking their medication regularly so they can experience the benefits of treatment.

"We must also increase our efforts to ensure that people who are unaware that they have HIV are tested, so they can receive care and treatment in a timely manner."

Some 36 million people have died from AIDS since it was first identified in the 1980s.

Though ARTs have added decades to the life expectancy of HIV-positive individuals, concerns remain about the medication's toxicity.

But the new study said "we can detect no indication of an increase in risk of death from any specific cause as a potential result of long-term adverse effects of ART."