Objective: Rheumatoid arthritis (RA) has been reported to be associated with bone loss during the first years of the disease. The magnitude of this problem after the initial years has not yet been evaluated. In the present study, the change in bone mineral density (BMD) in patients with recent-onset RA as well as the effects of inflammation, mobility, and the use of prednisone on this change were studied in the first decade of the disease.
Methods: BMD was measured twice in 76 RA patients with mean disease durations of 2.35 years at the first BMD measurement and 8.90 years at the second BMD measurement. BMD was measured in both hips using dual x-ray absorptiometry. Results were expressed as mean +/- SEM Z scores (using age- and sex-matched reference values) and as mean +/- SEM percent change in BMD (in gm/cm2) per year. The effects of inflammation, mobility, and the use of prednisone on change in BMD were evaluated using multiple linear regression analyses.
Results: At the first BMD measurement, RA patients had lower BMD compared with the reference values (Z score -0.42+/-0.11, 95% confidence interval [95% CI] -0.64, -0.20). Between the 2 measurements, we observed a small decrease in BMD of -0.28+/-0.11%/year (95% CI -0.07 to -0.49). However, the rate of bone loss was smaller than expected. The Z score increased by 0.13+/-0.05 between the 2 BMD measurements (95% CI 0.02, 0.23). Only the use of prednisone was significantly associated with increased bone loss. In a separate analysis that included only postmenopausal women, increased physical activity and longer time since menopause were both associated with decreased bone loss. In this subgroup of patients, the use of prednisone was significantly associated with increased bone loss as well. A high erythrocyte sedimentation rate was associated with increased bone loss, but this did not reach statistical significance.
Conclusion: After the initial years of the disease, bone loss in RA patients is lower than expected compared with age- and sex-matched reference values. Postmenopausal RA patients with low levels of physical activity are at increased risk of losing bone. Use of prednisone was the only variable consistently associated with reduction in BMD in RA patients.