Rate of bone loss on ART slows after the first year

A sub-study from the international START study provided reassuring data that the initial loss in bone mineral density (BMD) during the first year of ART, slowed during subsequent years,

The START study randomised more than 4600 participants to either starting ART immediately while the CD4 count was still about 500 or wait until it reached 350. The sub-study involving just over 200 people in each arm were presented by Andrew Carr from St Vincent’s Hospital, Sydney and colleagues from the INSIGHT research network.

Bone mineral density (BMD) was measured at the spine. hip and femoral head at baseline and annually. Mean percentage changes in BMD were calculated using both ITT and observed analyses (ie censoring data from the deferred ART group when treatment was started. The percentage of people on ART in the deferred arm was 18%, 28%, 58% and 85% after 1, 2, 3 and 4 years respectively.

In the ITT analysis which compared all participants by the initial randomisation, the initial 2% drop at both sites over the first year for the group on immediate ART converged over subsequent years, to show non-significant differences at the spine by year 3 (diff = –0.5%, p=0.26) and at the hip by year 4 (diif –0.2%, p=0.68).

In the observed analysis, significant differences at all three sites continued between groups at all time points, although a slower age-related reduction was seen over time.

Predictors of greater BMD decline in the deferred group included lower baseline CD4 count (-at the spine and neck)  and in the immediate group this was higher baseline viral load (in the hip and neck).

No differences were reported by choice of ART, although tenofovir DF was used by 83% of participants, efavirenz by 89% and PI by 13%.