Background Low bone mineral density (BMD) is highly prevalent in patients with systemic lupus erythematosus (SLE). However, the determinants of long-term BMD changes in SLE are still largely unknown, since the majority of studies performed had a cross-sectional design and the few longitudinal studies had a small sample size (maximum 36) and short follow-up duration (≤3 years).
Objectives The aim of this study was to assess the long-term BMD changes in patients with SLE and to identify the associated factors.
Methods We prospectively studied 126 SLE patients. Demographic and clinical data were collected and BMD measurements of the lumbar spine and total hip were performed by dual energy x-ray absorptiometry at baseline and at follow-up. Statistical analyses were performed using repeated measures t-test, Mann-Whitney U-test, univariate and multivariate regression analyses.
Results At baseline, osteopenia was present in 39.7% of the patients (90% female, mean age 39±12.2 years) and osteoporosis in 6.3%. After a median follow-up duration of 6.7 years (range 1.9 - 9.3 years), mean changes in BMD at the lumbar spine (-0.08%/year) and at the hip (-0.20%/year) were not significant. During follow-up, 70% of the patients used glucocorticoids. The mean ± SD daily glucocorticoid dose was 5.0±5.0 mg. In multiple regression analysis, BMD loss at the spine was significantly associated with higher daily glucocorticoid dose (p=0.004) and lower baseline 25-hydroxyvitamin D levels (p=0.030) whereas BMD gain at the spine was significantly associated with use of immunosuppressive medication other than glucocorticoids (p=0.016). BMD loss at the hip was associated with lower 25-hydroxyvitamin D levels (p=0.030), reduction of body mass index (p=0.040), and baseline use of antimalarials (p=0.006).
Conclusions In this 6-year follow-up study - thus far the largest study conducted -, bone loss was remarkably low. A dose-dependent relationship between glucocorticoid use and spine bone loss was found. In addition, use of antimalarials and lower 25-hydroxyvitamin D levels were associated with bone loss whereas use of immunosuppressive medication other than glucocorticoids was associated with bone gain at the spine. These findings underline the importance of prevention and treatment of vitamin D deficiency and osteoporosis in SLE, especially in patients using glucocorticoids or antimalarials. Moreover, the importance of treatment with immunosuppressive medication to improve disease-control and to reduce glucocorticoid dosages was highlighted.
Disclosure of Interest None Declared
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