A multicenter cross sectional study on bone mineral density in rheumatoid arthritis. Italian Study Group on Bone Mass in Rheumatoid Arthritis

Abstract

Objective: To determine the frequency of osteoporosis in a large cohort of women with rheumatoid arthritis (RA) and to investigate the main determinants of bone mineral density (BMD) and risk factors for vertebral fractures in this population.

Methods: We recruited 925 consecutive female patients with RA at 21 Rheumatology Centers in Italy. For each patient pre-registered demographic, disease, and treatment-related variables were collected. BMD was measured at lumbar spine and proximal femur by dual x-ray absorptiometry technique. Collected variables underwent a univariate and multivariate statistical procedure. Osteoporosis was defined as BMD > -2.5 T score.

Results: The frequency of osteoporosis in the whole sample was 28.8% at lumbar spine and 36.2% at femoral neck and increased linearly from Steinbrocker's functional stage I to IV (p = 0.0001). Patients with spinal or femoral osteoporosis were significantly older (p = 0.0001), had a lower body mass index (BMI) (p < 0.02), a significantly longer disease duration (p < 0.02) and a significantly higher Health Assessment Questionnaire (HAQ) score (p = 0.0001). These differences were significant, even after adjusting for age. Steroid use was associated with significantly lower lumbar and femoral BMD (p = 0.0001) even after adjusting for the main confounding covariates. Analysis of lateral spine radiographs revealed 74 women with at least one vertebral fracture. These women had a significantly lower lumbar and femoral BMD (p = 0.0001). The generalized linear model showed that steroid use, menopause, BMI, age, and HAQ were all significant independent predictors of lumbar and femoral BMD. The logistic procedure showed that age (OR 1.05, 95% CI 1.03-1.07), HAQ (OR 1.3, 95% CI 1.07-1.7), menopause (OR 1.9, 95% CI 1.1-3.2), use of steroids (OR 1.5, 95% CI 1.07-2.1), and BMI (OR 0.8, 95% CI 0.8-0.9) were significantly associated with the risk for osteoporosis. The only variables associated with an increased risk for vertebral fracture were age (OR 1.04, 95% CI 1.01-1.08), HAQ (OR 1.7, 95% CI 1.08-2.09), and cumulative steroid intake (OR for 1 g of prednisone 1.03, 95% CI 1.006-1.07).

Conclusion: To prevent osteoporosis and its dramatic complications in RA the therapeutic challenge is to preserve functional capacity using the lowest possible dosage of corticosteroids.