Results from a British study of HIV-positive men who have sex with men estimated a life expectancy of 75 years if HIV is diagnosed early, compared with 82 years for individuals without HIV. If HIV is diagnosed late, the researchers estimated life expectancy at 71.5 years.

The study authors noted that the decrease in life expectancy for HIV-positive men is comparable to the effect of cigarette smoking or having a chronic disease like diabetes.

“Men who have sex with men who are recently infected are estimated to have a good life expectancy, provided they are diagnosed early (and have good access to HIV care),” said Fumiyo Nakagawa, a researcher at UCL Medical School in London and lead author of the study.

“Our model has also estimated that life expectancy is further prolonged if the individual does not smoke, does not interrupt treatment, and has good adherence to treatment,” she added.

Life expectancy refers to the expected number of years of life remaining for an individual at a given age. In the general population, several factors, including sex, race, and lifestyle habits, are known to influence life expectancy. Various factors, like better drugs, earlier detection, and increased experience of physicians in treating HIV, are thought to contribute to increased life expectancy of people with HIV.

A Danish study published earlier this year found that HIV-positive individuals suffer from higher death rates mainly due to HIV and non-HIV related risk factors such as poor response to antiretroviral therapy, co-infection with hepatitis C or other diseases, and drug and alcohol abuse.

According to the study authors, most studies so far have based life expectancy estimates on current death rates in people with HIV. Since drugs’ ability to suppress the amount of HIV in the blood have improved over time, and since therapy benefits on death rates may take years to fully take effect due to slow increases in CD4 (white blood cell) counts, life expectancy for HIV-positive people may have been underestimated.

In this study, researchers used a computer simulation model of HIV infection and the effects of antiretroviral therapy to estimate life expectancy for a man who has sex with men and who becomes HIV positive in 2010 at the age of 30 years old. They also attempted to determine how life expectancy varied depending on how early or late HIV was diagnosed. For comparison, the researchers used general population death rates for men in the United Kingdom for 2009.

The model assumed that a man with HIV would start a non-nucleoside reverse transcriptase inhibitor (NNRTI)-based regimen, then switch to a boosted protease inhibitor-based regimen in the case of virologic failure.

The likelihood of treatment interruption was assumed to be 1.5 times higher in individuals with lower treatment adherence. Based on results from previous studies, a 1.5-fold increase in risk for all non-AIDS deaths was assumed for men with HIV throughout life.

Researchers also assumed a 40 percent chance of being a smoker and no hepatitis C co-infection.

Results showed that in a society with a high rate of HIV diagnosis, in which HIV was likely to be diagnosed soon after infection, the median age of death was estimated to be 75 years old. Risk of death within five and 10 years after infection was 2.3 percent and 5.2 percent, respectively. In addition, 57 percent, 78 percent, and 97 percent of men were diagnosed by three, five, and 10 years after infection, respectively.

Under this model, the median time from infection to diagnosis was 2.8 years, and the median CD4 cell count at diagnosis was 432 cells per microliter. In addition, the average time from infection to starting antiretroviral therapy was almost six years. Individuals were estimated to spend an average of 39 years on treatment, of which all but roughly seven years were spent actually receiving antiretroviral therapy (as opposed to periods of interrupted treatment).

The chance of treatment interruption at least once during an individual’s lifetime was estimated at 85 percent. Estimated life expectancy increased by 1.5 years when it was assumed that no treatment interruptions occurred.

It was estimated that 41 percent of individuals will at some stage progress to AIDS. However, only 14 percent of deaths were predicted to be from AIDS-related illnesses, and only 10 percent of men predicted to die of AIDS were also predicted to have resistance to all three major antiretroviral drug classes (nucleoside-reverse transcriptase inhibitors, NNRTIs, and protease inhibitors) plus integrase inhibitors.

Results also showed that in a society with a low HIV diagnosis rate, in which HIV was diagnosed only when symptoms were present, life expectancy for HIV-positive men who have sex with men was 71.5 years, indicating that an average of 10.5 years of life were lost compared to people without HIV.

With a low diagnosis rate, the median CD4 count was 140 cells per microliter at diagnosis; 22 percent, 37 percent, and 74 percent of individuals were diagnosed with HIV within three, five, and 10 years after infection, respectively. Consequently, there was a higher risk of death within 10 years after diagnosis (13 percent compared to 5.2 percent with a high diagnosis rate).

However, the effect of late diagnosis on life expectancy after this time was less significant due to the long-lasting effects of antiretroviral therapy, even in those who start treatment when CD4 cell counts are low.

The researchers estimated that the effect of late diagnosis would be greatest in the first 15 to 20 years after infection. Late diagnoses also increased the probability of transmitting HIV to others because lack of treatment increases risk of HIV transmission.

For more information, please see the study in the journal AIDS (abstract).