Peripheral bone density in patients with rheumatoid arthritis and factors which influence it

INTRODUCTION: Patients with rheumatoid arthritis (RA) frequently possess a number of risk factors for osteoporosis. Additionally, oral steroids are often used to control active rheumatoid disease and may further potentiate bone loss. We wished to establish the degree of peripheral bone loss in RA and to assess the influence of oral steroids and other risk factors. METHODS: We measured bone mineral density (BMD) in the non-dominant forearm using a DTX 200 osteometer in 191 RA patients who were receiving oral prednisone in a dose of at least 5 mg daily for over 3 months. We compared the results with those of two other groups: 165 RA patients who had never received oral prednisone and 242 normal controls without RA or any history of steroid therapy. Forward stepwise multiple regression analysis was used to determine the effects of age, disease variables and steroids on BMD. RESULTS: Age (P<0.001), RA (P<0.02) and steroid therapy (P<0.05) were all associated with reduced BMD using multiple regression analysis. Duration of RA was also associated with reduced BMD (P<0.05), but activity of disease was not. By WHO criteria (BMD T score<-2.5 S.D.), 95 (50%) of the RA steroid-treated patients (RAS) had osteoporosis, while 48 (25%) of the RA patients not exposed to steroids (RAN) were osteoporotic. Among the normal controls (NC), 48 (20%) had osteoporosis. The mean (S.D.) BMD Z scores for the three groups were -0.8 (1.3) for RAS, -0.4 (1.3) for RAN and 0.0 (1.0) for NC (P<0.01 for all differences). The percentages of patients with a Z score of -1 or less were 51% for RAS, 29% for RAN and 14% for NC. These differences were also significant (P<0.01). Male sex was associated with reduced BMD when compared to female sex (Z<-1) in the RAS (57 vs. 49%; P<0.05) but not in the RAN (25 vs. 31%) groups. For men with RA, the mean (S.D.) BMD Z scores were -1.3 (1.3) for RAS compared to -0.5 (1.3) for RAN (P<0.005), while for women the differences were less marked at -0.7 (1.3) for RAS compared to -0.4 (1.3) for RAN (P<0.05). CONCLUSIONS: In general, patients with RA have a significantly reduced forearm BMD, which correlates with increasing disease duration. Exposure to oral steroids increases bone loss, notably in male patients. Patients with RA on oral steroids need BMD measurements with a view to prophylactic therapy in those with a low result. Previous fractures and a daily dose of 15 mg or more of prednisone are also important factors in determining when prophylaxis is indicated.