Those who start antiretroviral (ARV) treatment for HIV soon after diagnosis, as is strongly recommended, experience a greater decline in bone mineral density compared with those who delay going on ARVs until their immune system deteriorates somewhat. Scientists randomized 399 HIV-positive individuals with a CD4 count greater than 500 to start ARVs immediately or wait until their CD4s dropped below 350. During an average 2.2 years of follow-up, those in the immediate and deferred treatment groups used ARVs for a respective 95 percent and 18 percent of the period. The researchers measured participants’ bone mineral density annually. Compared with those in the deferred treatment arm, those in the immediate treatment group saw their bone mineral density at the hip and spine decline during follow-up by 1.5 and 1.6 percentage points more than those in the deferred treatment group.