Risk Factors for Low Bone Mineral Density in Korean Patients with Systemic Lupus Erythematosus

ABSTRACT

OBJECTIVE: To determine the degree and risk factors for decreased bone mineral density (BMD) in patients with systemic lupus erythematosus (SLE). METHODS: One hundred and one patients with SLE and 57 age- and gender- matched healthy controls were enrolled in this study. The BMD was measured by dual energy X-ray absorptiometry (DXA). The laboratory findings and clinical variables evaluated in the SLE patients consisted of disease duration, SLE disease activity index (SLEDAI), and medications, including mean and cumulative dose of glucocorticoid. At the time of the clinical and laboratory assessment, the levels of serum osteocalcin, serum FSH/LH, urine deoxypyridinoline (DPD), and serum cytokines, such as IL-6 and soluble receptor activator of NF-kB ligand (RANKL), were determined in SLE patients using a enzyme-linked immunosorbent assay. RESULTS: The BMD T score decreased in patients with SLE compared to the healthy controls (-1.11 versus -0.41, p=0.001 at lumbar spine, -0.84 versus -0.01, p<0.001 at femur neck, -1.20 versus -0.45, p<0.001 at total hip, respectively). Osteoporosis and osteopenia was present in 16.8% and 46.5% of patients, respectively. Multiple regression analysis revealed a low BMD in the lumbar spine to be associated with increased FSH, low BMI and cumulative glucocorticoid dose. A low BMD in the hip and femur neck was associated with increased FSH, low BMI, and duration of glucocorticoid. On the other hand, the levels of osteocalcin, deoxypyridinoline (DPD), IL-6, and soluble RANKL were similar in patients with a low BMD and those with normal BMD. CONCLUSION: Osteoporosis and osteopenia are more common in young Korean SLE patients than in control subjects. Elevated FSH, low BMI, and the use of glucocorticoid are independent risk factors linked to a decreased BMD in Korean patients with SLE.