Results from a recent study show that HIV-positive people starting antiretroviral therapy today can expect to live nearly 16 years longer than counterparts who started therapy a decade earlier, but about 13 years shorter than people without HIV. The results also show that beginning antiretroviral therapy at an advanced stage of the disease significantly lowers life expectancy.

The study authors suggested that various factors, including better drugs, earlier detection, and increased experience of physicians in treating HIV, may have contributed to the rise in life expectancy.

The authors also suggested that the link between low pre-treatment CD4 (white blood cell) counts and shorter life expectancy may serve as a useful guide for HIV-positive people who are deciding when to start antiretroviral therapy.

However, the authors pointed out that a number of study participants were immigrants from Sub-Saharan Africa. This demographic difference may influence the relevance of the results to people with HIV in the United States.

Life expectancy at a given age is the expected number of years of life remaining. In the general population, several factors, including sex, race, and lifestyle habits, are known to affect life expectancy.

Although previous studies have examined mortality rates in HIV-positive people, estimates of how long people with HIV are likely to live have remained imprecise.

In their study, researchers at the University of Bristol sought to estimate how life expectancy for people starting antiretroviral therapy has changed over time. They also attempted to determine how life expectancy was affected by how early or late people initiated therapy.

The researchers analyzed data from 17,661 participants who started antiretroviral therapy in clinics across the U.K. from 1996 to 2008. All participants were over 20 years of age, 75 percent were men, and 58 percent were white.  All participants had CD4 counts of 350 cells per microliter or less when they started treatment.

The researchers collected data in four time intervals starting from 1996 to 1999 and ending with 2006 to 2008 to estimate how life expectancy at age 20 changed over time. They then compared these values to the life expectancy at age 20 of the general population. The researchers also determined whether life expectancy in people with HIV depended on factors such as sex and pre-treatment CD4 counts.

Results showed that persons starting antiretroviral therapy in 2006 to 2008 could expect to live nearly 46 years after the age of 20, while their counterparts who started treatment in 1996 to 1998 could expect to live for 30 years after the age of 20.

Results also showed that the life expectancy for HIV-positive people at age 20 is still lower than that of the general population by about 13 years. In addition, while in the general population women could expect to outlive men by nearly four years, in the HIV-positive population women could expect to outlive men by almost 11 years. The researchers suggested that this could be because women are screened for HIV during pregnancy and are therefore diagnosed earlier, or because of lifestyle differences such as alcohol and drug use.

Participants whose pre-treatment CD4 counts were less than 200 cells per microliter had a significantly lower life expectancy (38 to 41 years after age 20) than those with counts between 200 and 350 cells per microliter (53 years after age 20).

A total of 7 percent of participants died during the course of the study.

For further information, please see the related article in the British Medical Journal.