People who become infected with HIV after the age of 30 have a better response to antiretroviral (ARV) therapy than people who become infected at a younger age, according to a study published in the September 1 issue of the Journal of Acquired Immune Deficiency Syndromes.

Before effective combination ARV therapy was introduced in 1996, many studies found that older adults had faster HIV disease progression than young adults and responded less well to treatment. Since 1996, studies have been mixed, with some finding that older adults fair better and others suggesting an advantage for young adults. Most studies, however, have focused solely on the age at which a person started ARV treatment rather than the age at which he or she became infected with HIV, which might ultimately be a better predictor of treatment responses.

Amy Weintrob, MD, from the Walter Reed Army Medical Center in Washington, DC, and her colleagues examined the medical records of a group of 541 armed services personnel who became infected with HIV after 1996 and later started ARV therapy. Nearly all of the patients were male, and 46 percent were African American. The majority became infected between ages 18 and 39, and very few became infected after age 50.

Dr. Weintrob’s team found that older age at the time of infection was associated with a better response once ARV treatment was initiated, including: the likelihood of achieving a viral load of less than 500 copies after six months of treatment, the likelihood of sustaining an undetectable viral load and greater increases in CD4 counts.

Slight differences in age-related responses among different racial groups were also reported. Among African Americans, better responses were seen in those infected with HIV after age 30. In white patients, better responses were seen in those infected with HIV after age 20.

While a number of studies have found that younger adults have poorer adherence than older adults, adherence alone did not appear to account for the difference in responses to treatment in this study. The study authors call for further research to determine what elements may account for the different treatment responses they observed, both by age and by race.