Increasingly effective therapy to manage HIV infection and to prevent and treat AIDS-related complications has provided 3 million years of extended life to Americans with HIV since 1989, according to a new report published in the June 1st issue of the Journal of Infectious Diseases.

Dr. Rochelle Walensky of Harvard Medical School and her colleagues calculated that advances in HIV care have yielded a total survival benefit of 2.8 million years in the United States. Dr. Walensky’s group also estimated that drugs to prevent mother-to-child transmission of HIV have averted 2,900 infant infections, saving an additional 137,000 years of life. The model projected that a person initiating HIV therapy in 2003 could expect to live more than 13 years longer than if he or she had been diagnosed in 1988.

The researchers used a computer model that incorporates literature-based data of clinical measures including HIV viral load, T-cell counts, efficacy of combination drug therapy, and incidence of opportunistic infections, to simulate HIV disease progression both with and without treatment.

The investigators defined six eras of AIDS treatment between 1989 and 2003. In the first two periods, 1989 to 1992 and 1993 to 1995, drugs became available to prevent two common infections – Pneumocystis jiroveci pneumonia (PCP) and Mycobacterium avium complex (MAC). Although the drugs provided an average per-person survival benefit during that time of only 2.6 months, Dr. Walensky’s group noted that those early eras helped to shape the perception that AIDS was a treatable condition. The researchers subdivided the combination drug treatment era, which began in 1996, into four periods corresponding to increasingly effective drug regimens and other advances in HIV care.

For each year of the six eras, the investigators ran simulations of HIV disease progression in two equal-sized groups of hypothetical people with AIDS. One group received no therapy, while the other group received all available therapies of that era. The model calculated a per-person survival benefit and a total survival benefit in each era. By 2003, the model projected that an individual beginning treatment that year could expect to live more than 13 years longer than if he or she had been diagnosed in 1988. The total survival benefit for the 24,780 people diagnosed with AIDS and entering care in 2003 was 330,189 years. The total cumulative survival benefit across all eras from all forms of HIV therapy was 2.8 million years.

Dr. Walensky emphatically notes, however, that survival benefits related to therapy are available only to those with known HIV infection. But about one-fourth of people in the United States infected with HIV are unaware of their infection. According to Dr. Walensky, “these findings underscore the importance of expanded HIV testing and better linkage to care for people who are HIV-infected, so that more of them can realize the life-extending benefits of HIV therapies.”