Duration of HIV infection and duration of HIV therapy use risk factors for bone disease

The risk of developing the bone-wasting disease osteonecrosis becomes higher the longer someone has been both HIV infected and taking potent anti-HIV therapy, according to study published in the August edition of AIDS. Another recently published study found that pre-existing risk-factors often led to the development of osteonecrosis in HIV-positive patients.

Osteonecrosis is a disease resulting from the temporary or permanent loss of the blood supply to the bones. Without blood, the bone tissue dies and causes the bone to collapse. It most commonly affects the hip and knee.

In the 1990s it was suggested that HIV-positive individuals had an increased risk of osteonecrosis. Research has also pointed to the possibility of a link between the disease and some antiretroviral drugs- particularly protease inhibitors (Safrin 1999).

Why this disease has emerged as a problem for people with HIV has puzzled clinicians and investigators aimed to find out whether the risk of osteonecrosis increased with the duration of HIV infection, the duration of potent HIV therapy, or both.

Data from over 5,300 people included in the French Hospital Database on HIV were examined. The incidence of osteonecrosis was rare, being diagnosed in just 104 individuals, most of the cases affecting the hip (80%). The researchers then reviewed the notes of patients to find which factors increased an individual’s risk of developing the disease.

Three main factors were discovered. The first was whether a person had ever developed an AIDS-defining illness. This increased the risk of osteonecrosis three-fold. The second factor was a very low CD4 count in the past. If someone’s CD4 cell count had ever dropped to between 50 and 199 cells/mm³ it put them at a 60% increased risk of osteonecrosis. That figure went up to 80% if the CD4 cell count had ever dropped to below 50 cells/mm³. Both factors were interpreted by the investigators as good indicators of how long an individual had been infected with HIV.

Finally, the length of time a person had been taken HIV therapy increased the risk. Compared to HIV-infected people who had never taken antiretroviral drugs, the risk of osteonecrosis went up 2.6 times in people treated for longer than twelve months and over five times in those treated for longer than five years.

The authors say this is the first study to show that the risk of osteonecrosis increases with the duration of both HIV infection and highly active antiretroviral therapy (HAART).

They say it would be interesting to study whether any particular drugs are associated with an increased risk, but this is not possible using these data. They also point out that, although osteonecrosis is still a relatively uncommon disease, the risk must be considered in HIV-infected people who develop bone pain, especially if they have advanced HIV disease or have been on potent antiretroviral therapy for a long time.