Recently Brown et al. also reported an association between low baseline CD4 cell count and subsequent BMD loss [18]. Studies of BMD evolution after receipt of antiresorptive agents, vitamin D or calcium supplementation have confirmed that alterations in bone resorption and formation may not occur simultaneously during the first remodelling cycle after an intervention [19], and consequently Aloia et al. argue that studies of agents that affect bone remodelling must http://www.selleckchem.com/screening/fda-approved-drug-library.html be carried out for at least two bone remodelling cycles, corresponding to at least 1 year, before long-term affects can be assessed

[19]. A large randomized study (n=602) of tenofovir- vs. stavudine-based HAART also found that spine BMD declined for the first 24 weeks and then stabilized, while hip BMD declined for 48 weeks before stabilizing [7]. The hip has more cortical bone than the lumbar spine, which has mainly trabecular bone, and as bone remodelling is more rapid for trabecular than for cortical

bone [20], a new balance between formation and resorption may take longer to occur in the hip. In accordance with our findings, several prospective studies that did not include the period immediately after HAART initiation did not show accelerated bone loss over time [4,5,21] or even showed Selleck Linsitinib that BMD increased compared with HIV-negative controls [3]. The SMART BMD substudy (n=214) was mainly driven by treatment-experienced patients, and the SMART investigators observed an ongoing decline in BMD at both spine and hip, with a yearly rate of 0.4 to 0.9%. The largest decrease was observed in

the continuous treatment arm vs. the drug conservation arm [8,9]. As in other studies without an CYTH4 HIV-negative control group, the interpretation of data should take into account that fact that healthy men have decreasing BMD from age 25 years, with an annual decline of up to 0.5% in the hip [22,23]. The data showing an increase in BMD in the drug conservation arm within the first year after discontinuation of HAART could also be interpreted as a temporary imbalance between formation and resorption, resulting in a transient increase in BMD after HAART discontinuation, which is the opposite pattern to that seen after HAART initiation. There is a lack of prospective studies following HIV-infected patients before HAART initiation, but the relatively low BMD at baseline suggests that BMD loss may also occur before HAART initiation. Furthermore, low BMD has been linked to duration of HIV infection [24]. The BMD decline in untreated individuals could be mediated by effects of HIV infection or immunosuppression acting directly or indirectly through factors such as low body weight, malnutrition and chronic inflammation.