HIV infection is associated with loss of bone mineral density and an increased risk of fractures. Loss of bone continues after HIV therapy is started, and decreases in BMD of between 2 and 6% typically occur in the first two years of antiretroviral therapy.
…“We found that even after controlling for multiple confounders such as BMI that there was a robust relationship between low baseline CD4+ count and greater bone loss after ART [antiretroviral therapy] initiation,” comment the authors. “The underlying reason for the relationship between low baseline CD4+ count and bone loss with ART initiation is not known but suggests a potential role for the immune system in skeletal maintenance.”
Older age (each additional year, p < 0.001), female sex (p = 0.007), low BMI (p < 0.001) and a high HIV viral load (p = 0.002) were also associated with greater bone loss.
…There was also a significant interaction between lower CD4 cell count and higher viral load and BMD loss (p = 0.043). In patients with a higher viral load, the negative effect of a low CD4 cell count on BMD was greater than in individuals with a lower viral load.
The investigators note that the BMD changes found in their study were relatively “modest” and of unknown clinical significance. They also emphasise that they did not have data on some factors associated with bone loss such as tobacco and alcohol use, testosterone and vitamin D levels, and use of medicines that can affect BMD.
Perhaps the more immunity resources a body has to allocate for fighting infection/inflammation, the less is available for skeletal maintenance? In any case, if certain ART is associated with bone loss just like HIV is, then, unofficially, ART is contributing to an AIDS-defining illness; particularly if skeletal maintenance is intimate with the immune system.