Osteoporosis in systemic lupus erythematosus: factors associated with referral for bone mineral density studies, prevalence of osteoporosis and factors associated with reduced bone density.

The purpose of this study was to evaluate the clinical characteristics of women with systemic lupus erythematosus (SLE) sent for a dual energy X-ray absorptiometry (DEXA) study, and to analyse the factors associated with a lower bone mineral density in these patients. Women with SLE who had a DEXA done between 1 January 1995 and 31 December 2000 were compared with those who did not have DEXA scans performed. SLE patients with osteoporosis (OP) were compared with those with a normal bone density. Of 516 women with SLE, 205 had a DEXA done. These patients had more traditional risk factors for osteoporosis, higher lupus disease activity, renal involvement, increased damage, higher mean steroid dose, increased use of immunosuppressants and occurrence of avascular necrosis. Of the 205 patients with DEXA, 18% had osteoporosis, 48.8% had osteopenia and 33.2% had normal bone mineral density. The two statistically significant predictors of a low bone density were a higher age at time of DEXA (P = 0.0003) and a higher SDI score (P = 0.0019). Osteoporosis is a significant comorbidity in SLE. Lupus patients referred for a DEXA have more traditional risk factors and use more corticosteroids. The main factors associated with a low bone density were however found to be age and increased damage. Interestingly, disease activity and corticosteroid use were not associated with osteoporosis in this study which may suggest other potential causes such as decreased physical activity associated with damage.