This study will look to see if there are changes in the blood cells that are associated with bone disease and sort out effects that are due to the HIV virus itself, the medications and see if faster aging occurs in the cells of HIV infected persons. Bone disease will be measured by a special X-ray called a DEXA scan. A DEXA scan is used by doctors to see if someone has normal bone mass for their age or if there is thinning of the bones.

The purposes of this study are:

• to learn how common bone disease is in HIV infected patients over the age of 50 years that receive their care at the CORE Center
• to see what are the common causes of bone disease in older HIV infected persons
• to see if there are differences in blood cells and levels of cytokines in patients who do or do not have bone disease, as this may help researchers determine the cause of bone disease.

Inclusion Criteria:

• HIV-1 infection documented by ELISA and confirmed by western blot
• Treatment with antiretroviral drugs for at least 12 months
• Age 50-70 years
• CD4 count > 350 cells/mm3 for at least 6 months
• HIV-RNA undetectable (< 75 copies/ml for at least 6 months)

Exclusion Criteria:

• Known bone disease (primary or metastatic malignancy, osteomalacia)
• Treatment for bone disease (bisphosphonates, calcitonin, strontium, sodium fluoride, synthetic PTH, or high-dose vitamin D [> 800 IU daily]).

100 HIV-infected adults, age 50 years or older, on HAART with undetectable viral loads, who are randomly sampled from 6 strata defined by ethnicity (Black:White:Hispanic; 2:1:1) and sex (male:female; 1:1).

100 HIV+ adults, age ≥ 50 yr (50 ♂, 50 ♀; 50 AA, 25 W, 25 H).