Low Bone Density Tied to Incident Fracture in Two U.S. HIV Cohorts
Osteoporosis determined by DXA scan quadrupled the risk of subsequent fracture, and current or former tobacco use raised the risk almost 60% in a 1,000-person analysis of two U.S. HIV cohorts. The findings in this middle-aged group suggest that HIV-positive people younger than 50 years old may benefit from DXA (dual energy X-ray absorptiometry) scans for bone mineral density (BMD).
Plentiful research confirms high rates of low BMD and fracture in HIV-positive people. Although logic suggests that low BMD (osteopenia or osteoporosis) makes fractures more likely, research has not systematically addressed this association in people with HIV. To address that need, researchers working with two large U.S. HIV cohorts -- the HIV Outpatient Study (HOPS) and the Study to Understand the Natural History of HIV/AIDS in the Era of Effective Therapy (SUN) -- conducted this prospective analysis.
The study population consisted of HOPS and SUN participants who had at least one lumbar spine and femoral neck DXA scan starting in 2008 in HOPS and 2004 in SUN. Follow-up continued until June (SUN) or September (HOPS) 2012. Researchers used the standard definition of low BMD, with a T-score > -2.5 to < -1.0 indicating osteopenia and ≤ -2.5 indicating osteoporosis. The HOPS/SUN team defined incident fracture as the first fracture that occurred after a person's first DXA scan. The analysis did not exclude people with a fracture before their DXA. Fractures of the hip, spine, shoulder and forearm are considered osteoporotic. The researchers used multivariable proportional hazards regression to analyze the association between low BMD and risk of subsequent fracture.
The analysis included 1006 people with a median age of 43 years (interquartile range 36 to 49), 83% of them men, 69% men who have sex with men (MSM), 67% white, 21% black and 9% Hispanic. Median CD4+ count stood at 461 cells/mm3, median nadir CD4+ count at 188 cells/mm3 and median body mass index at 24.9 kg/m2.
While 611 people (61%) had normal BMD at the femoral neck, 358 (36%) had osteopenia and 37 (4%) had osteoporosis. Through a median follow-up of 3.2 years after a first DXA, 85 people (8.4%) had a new fracture for an incidence of 2.09 per 100 person-years. Most fractures involved the ribs or sternum (n = 18), the hand (n = 14), the foot (n = 13) or the wrist (n = 11). There were 22 major osteoporotic fractures.
In the final multivariable model, two factors independently predicted incident fracture: Osteoporosis on the first DXA scan quadrupled fracture risk (adjusted hazard ratio [aHR] 4.02, 95% confidence interval [CI] 2.02 to 8.01, P < .001) and current or former smoking raised the risk almost 60% (aHR 1.59, 95% CI 1.02 to 2.50, P = .042). Osteopenia did not affect fracture risk (aHR 1.17, 95% CI 0.74 to 1.84, P = .51). Other variables that did not affect fracture risk included hepatitis C infection and nadir or current CD4+ count. The low number of major osteoporotic fractures in this study group precluded statistical analysis limited to these fractures. In a separate analysis, factors associated with osteopenia or osteoporosis included older age, lower nadir CD4+ count, MSM HIV transmission risk and prior fracture.
The researchers note that most people in their study were younger than 50, the minimum age recommended for DXA scans in people with HIV. The authors believe their findings "suggest the need to reconsider when to screen for low BMD in HIV-infected patients," adding that early detection of low BMD "provides opportunity for earlier intervention to help prevent fractures in HIV-infected persons."