Background Rheumatoid arthritis (RA) is an independent risk factor for osteoporosis. Patients with RA have a higher risk of fractures than healthy individuals1. We previously reported that bone mineral density (BMD) is lower in patients with RA than in healthy individuals2. Whether or not BMD and fracture correlate in patients with RA has remained unclear.
Objectives We aimed to determine whether whole body BMD could predict fracture during five years of follow in patients with RA.
Methods This prospective cohort study analyzed data collected over a period of five years from the TOMORROW study (TOtal Management Of Risk factors in Rheumatoid arthritis patients to lOWer morbidity and mortality clinical trial (registration number, UMIN000003876)), which is a 10-year prospective study of 208 age and sex matched patients with RA and 213 volunteers (controls). The BMD, lean body mass, and fat ratio (%) were measured using whole body dual-energy X-ray absorptiometry (DXA). Patients and volunteers who had received metal implants were excluded. We measured BMD, lean mass, and fat ratio (%) at baseline between groups with and without fractures, to identify a cut-off for increased risk of fracture using ROC curve analysis.
Results Fracture rates did not significantly differ between RA patients and controls (14.9% vs. 10.4%; p=0.231) over the five-year period. The DXA data derived from a total of 358 participants (158 patients and 200 controls) identified 39 individuals with and 319 without fracture. The BMD was significantly lower in the group with fracture, than that without (0.914 vs. 0.995 g/cm2, respectively: p=0.001 and the tendency was the same in the patients with RA (0.873 vs. 0.977 g/cm2, respectively; p=0.002). Lean mass and fat percentage did not significantly differ between the groups with and without fracture. At a BMD cut-off of 0.869 g/cm2, the area under the curve was 0.734, sensitivity was 72.2% and specificity was 65.7% (p=0.01) in patients with RA (Figure 1 and Table 1). The odds ratio of fracture among the patients with RA over a period of five years was 5.3 when the BMD was <0.869 g/cm2.
Conclusions The baseline BMD was significantly lower in the group with, than without fracture. However, lean mass and fat percentage did not significantly differ between them. Baseline total BMD was more useful than lean mass and the fat percentage to predict fracture within five years among patients with RA.
van Staa, T. P., Geusens, P., Bijlsma J. W., et al. Clinical assessment of the long-term risk of fracture in patients with rheumatoid arthritis. Arthritis Rheum. 2006; 54:3104–12.
Tada, M., Koike, T., Inui, K., et al. Factors predicting change in bone mineral density in patients with rheumatoid arthritis: the TOMORROW study. EULAR 2014 poster (FRI0077)
Disclosure of Interest None declared