Objective: To study the BMD of patients with SLE according to the age of disease onset.
Methods: Consecutive SLE patients were screened for BMD at the hip, lumbar spine and whole body by the dual-energy X-ray absorptiometry (DXA). Comparison was made between patients who had disease onset in childhood (<18 years) and adulthood (≥18 years). Factors associated with low BMD were studied by linear regression.
Results: A total of 395 SLE patients were studied (94% women; 11% childhood-onset disease). Osteoporosis of the lumbar spine and the hip/femoral neck was present in 20 and 10% of the patients, respectively. Childhood-onset SLE patients were less likely to be post-menopausal, but had significantly lower BMI, longer SLE duration and a higher frequency of ever use of high-dose CSs, CYC and AZA. Despite a significantly younger age, the BMD of the hip, femoral neck and lumbar spine was significantly lower in childhood- than adult-onset SLE patients. In linear regression models, childhood-onset disease was an independent factor for lower BMD at the lumbar spine (β = -0.18; P = 0.002), hip (β = -0.20; P = 0.001) and femoral neck (β = -0.16; P = 0.01) after adjustment for age, sex, BMI, smoking, menopause, SLE duration and damage index, duration and current dose of prednisolone treatment and the ever use of high-dose glucocorticoids, other immunosuppressive agents, calcium, vitamin D and the bisphosphonates.
Conclusions: In adult SLE patients, childhood-onset disease carries a higher risk of osteoporosis, which may possibly be related to a higher cumulative dose of glucocorticoids used for more active disease and failure to achieve a normal peak bone mass during puberty.