Prevalence and associated factors of low bone mass in adults with systemic lupus erythematosus

Background Systemic lupus erythematosus (SLE) patients are often treated with glucocorticoids, which place them at risk of bone loss. Objectives The objectives of this article are to determine: (1) the prevalence of low bone mineral density (BMD) and factors associated with low BMD and (2) the prevalence of symptomatic fragility fractures in inception patients of the Toronto Lupus Cohort (TLC). Methods Prospectively collected data from the TLC (1996-2015) of inception patients' first BMD were analyzed. For pre-menopausal women/males <50 years, BMD 'below expected range for age' was defined by Z-score ≤ -2.0 SD. For post-menopausal women/males age 50 or older, osteoporosis was defined by T-score ≤ -2.5 SD and low bone mass by T-score between -1.0 and -2.5 SD. Patients' BMDs were defined as abnormal if Z-score ≤ -2.0 or T-score < -1.0 SD, and the remainder as normal. Descriptive analysis and logistic regression were employed. Results Of 1807 patients, 286 are inception patients with BMD results (mean age 37.9 ± 13.7 years); 88.8% are female. The overall prevalence of abnormal BMD is 31.5%. In pre-menopausal women ( n = 173), the prevalence of BMD below expected range is 17.3%. In post-menopausal women ( n = 81), the prevalence of osteoporosis and low BMD are 12.3% and 43.2%, respectively. Age and cumulative dose of glucocorticoids are statistically significantly associated with abnormal BMD in multivariate analysis. Of 769 inception patients from TLC, 11.1% experienced symptomatic fragility fractures (peripheral and vertebral) over the course of their disease. Conclusion The prevalence of low BMD is high in SLE patients, and is associated with older age and higher cumulative glucocorticoid dose.