Three million years of life saved by AIDS care in the United States

Researchers have used a computer-based model to calculate that treatment of patients with AIDS led to at least 2.95 million years of life being saved between 1989 and 2003 in the United States. The results were published in the 1st July edition of The Journal of Infectious Diseases.

The researchers, from Boston, New Haven and New York City, used the model to estimate that the treatment of AIDS patients led to 2.81 million years of life being saved. In addition, treatments to prevent HIV being passed from mothers to their babies have saved another 137,000 life-years.

They claim that this reflects the dramatic effect that HIV research, development and treatment have had on the epidemic in the United States. However, they argue that better access to testing and treatment could have an enormous effect on the epidemic, not only in the United States, but globally.

The investigators defined six separate eras of HIV treatment, from the introduction of preventative treatments for Pneumocystis pneumonia (PCP) in 1989 and by the addition of prophylaxis for Mycobacterium avium intracellulare (MAI) in 1993. 1996 saw the introduction of protease inhibitors and highly active antiretroviral therapy, followed by three more stages of improved HIV treatment: non-nucleoside reverse transcriptase inhibitors in 1998, ritonavir-boosted protease inhibitors and resistance testing in 2000, and improved drug effectiveness and tolerability, plus the addition of T-20 (enfuvirtide, Fuzeon), in 2003.

The investigators used published data on the numbers of people in the United States with AIDS to calculate the survival rates across these six eras. By including published information on the CD4 cell counts and viral loads of patients with AIDS, as well as the risk of resistance developing and the effectiveness of treatment regimens, they simulated the disease progression of cohorts of one million hypothetical patients. They then compared these survival rates to hypothetical simulations of patients receiving no treatment.

“Projected per-person survival after an AIDS diagnosis increased from 19 months (1.6 years) in the absence of treatment to 179 months (14.9 years) by 2003, a gain of 160 months (13.3 years),” the investigators write. “This survival benefit greatly exceeds that achieved for patients with many other chronic diseases in the United States.”

The investigators went on to work out the total numbers of years of life saved by multiplying their per-person survival rates by the published numbers of AIDS patients receiving care in the United States.

They also estimated the numbers of lives saved by treatment of pregnant women to prevent transmission to their babies, based on published birth rates, rates of treatment uptake, HIV transmission rates and life expectancies of babies born with and without HIV. Between 1994 and 1999, treatment with AZT (zidovudine, Retrovir) alone contributed a further 51,600 years of life saved. This was followed by an additional 85,800 years in the era of combination treatment between 2000 and 2003, equivalent to a total prevention of 2900 new HIV infections.

The investigators deliberately made their analysis conservative, by excluding the effects of single- or dual-drug HIV treatment before 1996, using low estimates of the number of patients receiving care and the effectiveness of treatments, only considering patients with AIDS diagnoses, and excluding any benefits of treatment in reducing HIV transmission. However, they calculated that by relaxing these estimates, the true amount of life saved could be over 5.2 million years.

They also excluded the toxic effects of antiretroviral therapy on survival rates, such as heart disease and diabetes. “This exclusion is unlikely to have had a major impact on the analysis,” they claim. “This increase is greatly outweighed by the absolute reduction in the risk of AIDS-related complications from antiretroviral therapy.”

The investigators reported that up to 26% of HIV-positive people in the United States are unaware of their infection, and only 57% of patients were accessing care. They calculated that expanding HIV testing and care could lead to a further 740,000 years of life being saved, if all AIDS patients received appropriate care after their diagnosis.

This theme is taken up by Sten Vermund of Vanderbilt University in an accompanying editorial. After reflecting on the enormous benefits that AIDS treatment has brought about, Dr Vermund calls for the introduction of HIV testing into routine medical care and the abolition of pre-test counselling, to improve diagnosis rates and increase the number of lives saved.

“The millions of life-years saved in the United States should re-invigorate policy debates as to how best to identify HIV-infected persons in our country by offering and encouraging testing as a routine part of medical screening,” he writes. “We must reduce barriers to care, the first of which is the difficulty with which a test is obtained in many venues.

“We now face a daunting challenge to do better,” he adds. “If we address systematically the barriers to testing, care, and prevention, then future modellers will describe the next 15-year period as having saved hundreds of millions of life-years, not just in North America but around the globe.”