Add one more complication to uncontrolled HIV infection - damaged lungs.

In an observational study, people with uncontrolled HIV infection experienced a loss in lung function at a sharply higher rate than both HIV-negative people and those with good viral control, according to Michael Drummond, MD, of Johns Hopkins University.

The decline was “statistically and probably clinically significant as well,” Drummond said during a press conference at the annual Conference on Retroviruses and Opportunistic Infections (CROI).

The finding adds urgency to efforts to counsel HIV patients on the importance of smoking cessation, Drummond said.

Lung function, as measured by one-second forced expiratory volume (FEV1) during spirometry, declines normally with age and is also significantly impacted by smoking, Drummond noted. But in a large cohort of injection drug users - 95% of them with a history of smoking and 88% still lighting up during the study - HIV also emerged as an independent risk factor for increased lung function decline, he said. The researchers had repeated lung function measurements over almost three years for 1,064 members of the cohort, including 30% who were HIV-positive. Of the HIV-positive participants, Drummond said, only 55% were on highly active anti-retroviral therapy and 10% had uncontrolled disease, defined as a plasma viral load of 75,000 or more copies of HIV RNA per milliliter. They also stratified HIV-positive participants by the number of CD4-positive T cells per cubic millimeter of blood. For both viral load and the immune system, Drummond said, “markers of advanced and uncontrolled HIV were associated with a more rapid decline in lung function.” On average, HIV-negative participants lost 23.6 mL a year in FEV1, compared with 37.5 mL a year for the HIV-positive participants as a whole - a difference that was not significant. HIV-positive participants with a viral load of more than 75,000 copies lost 99.1 mL a year, which was significantly worse than the others at P<0.01. HIV-positive participants with a CD4 count of less than 100 lost 80.8 mL a year, compared with 26.3 mL a year for those with a CD4 count above 200, a significant difference of P<0.01. Drummond told MedPage Today that better HIV control appears to be associated with a less sharp decline in lung function. In most situations, smoking would complicate the analysis, he noted, but because tobacco use was almost universal in the cohort, it was possible to essentially ignore its effects. Lung function decline is "a relatively new topic" for HIV specialists, commented Andrew Carr, MD, of the University of New South Wales in Sydney, who was not part of the study, but who chaired the CROI press conference. And it remains unclear what pathophysiological mechanisms cause the effect seen by Drummond and his colleagues, he told MedPage Today. He noted that HIV may damage the parts of the immune system that help keep the lungs in good health, either allowing disease or perhaps slowing the process of repair after illness. It will be important to learn whether effective HIV therapy prevents the decline in lung function. Carr noted that some important information might come from the NIH-funded START trial, which is investigating the effects of early versus delayed initiation of anti-retroviral therapy. Researchers will be tracking lung function among participants as part of that trial.