Predictors of fracture risk in patients with systemic lupus erythematosus

Objectives Bone loss in systemic lupus erythematosus is multifactorial. Recent studies demonstrate corticosteroids, previous fractures and increasing age decrease bone mineral density. The effect of body mass index and fat mass are less well characterized. We sought to determine fracture risk factors in patients undergoing dual-energy X-ray absorptiometry scanning at a district hospital in 2004-2015. Methods Standard dual-energy X-ray absorptiometry parameters were recorded, plus rheumatoid arthritis diagnosis, smoking status, alcohol consumption, family history of fractures, history of secondary operation and corticosteroid use. Data were analyzed using Fisher's exact test for categorical data and logistic regression for continuous data. Results One hundred and fifty patients (141 women, nine men) with SLE were included; 52 (34.6%) had sustained at least one fracture. Fracture risk increased with increased age, body mass index, fat mass and average tissue thickness, and decreased lean mass (adjusted for steroid use), as well as with smoking and rheumatoid arthritis. Increased femoral and vertebral bone mineral density conversely decreased fracture risk. Conclusion Our study suggests increased age, body mass index, fat mass, smoking and/or rheumatoid arthritis increase fracture risk in SLE patients. To our knowledge, this is the first demonstration of a correlation between increased fat mass, adjusted for steroid use and fracture risk, in adults, potentially indicating a differential effect of fat on bone metabolism and lessening of lean body mass.