The Prevalence of Low Bone Mineral Density in Brazilian Patients With Systemic Lupus Erythematosus and Its Relationship With the Disease Damage Index and Other Associated Factors

Abstract

The aim of this study was to examine the prevalence of osteoporosis, osteopenia, and bone mineral density (BMD) less than the expected range based on age in patients with systemic lupus erythematosus (SLE) in a tropical region of Brazil and the relationship between reduced BMD and several associated factors, especially the SLE disease damage index (SDI). We scored 159 patients with creatinine clearance of 60mL/min or more for SDI, which was modified by excluding the osteoporosis item. For postmenopausal women and men older than 50yr, T-scores identified osteopenia (<−1.0 and >−2.5) and osteoporosis (≤−2.5). For all patients, a Z-score of −2.0 or less identified BMD less than the expected range for age. Other variables that influence BMD were studied. The prevalence of osteoporosis, osteopenia, and BMD less than the expected range for age was 28%, 54%, and 29.6%, respectively. The Z-scores were significantly lower in patients with a modified SDI≥1 (mean±standard deviation [SD]=−1.45±1.18) compared with patients with a modified SDI=0 (mean±SD=−0.94±1.01; p=0.01). The lowest Z-score had a significant association with postmenopausal status (p=0.038) and significant correlations with the duration of glucocorticoid (GC) usage (p=0.033, r=−0.17), the cumulative amount of GC (p=0.000, r=−0.28), and parathyroid hormone levels (p=0.003, r=−0.24). A multiple linear regression revealed that the modified SDI (p=0.003) and the cumulative amount of GC (p=0.006) had significant independent associations with the lowest Z-score. In conclusion, a BMD less than the expected range for age occurs frequently in Brazilian patients with SLE independent of the renal failure. The patients with greater SDIs had lower Z-scores, which suggests a direct association between chronic inflammation from disease and a reduced BMD.