Reduced bone mineral density in early rheumatoid arthritis is associated with radiological joint damage at baseline and after 2 years in women

Objective. Data suggest that reduced bone mass may be associated with radiological damage in rheumatoid arthritis (RA). We investigated if patients with reduced bone mineral density (BMD) at onset of RA had more radiological damage at onset and after 2 years than patients with normal BMD. Methods. BMD at lumbar spine and hip was measured in 204 patients with recent RA at presentation. At baseline and after 2 years, radiographs of hands and forefeet were evaluated according to the Larsen method. At the same time-points, Disease Activity. Score (DAS 28) and functional disability (the Stanford Health Assessment Questionnaire, HAQ) were assessed. Results. The 134 women and 70 men had a mean age of 55 and 61 years, respectively. Reduced bone mass (RBM, Z score less than or equal to 1.0 SD) in at least one site was found in 46.0% of women and 62.5% of men. T and Z scores correlated significantly with Larsen scores both at baseline and after 2 years for the total patient cohort. Calculated separately for the sexes, significant correlations were found only for women. Women but not men with reduced bone mass and osteoporosis had higher Larsen scores at baseline and after 2 years than those without. From a stepwise multiple logistic regression analysis Z score trochanter and baseline C-reactive protein were selected as independent predictors of joint damage, measured as proportion over the median Larsen scores. This model could explain about 25% of the "variance" in outcome (Nagelkerke R-2 = 0.27). Conclusion. Reduced BMD at onset of RA in women was associated with a higher Larsen score at baseline and after 2 years, indicating that the development of reduced bone mass and joint destruction in RA may have a common pathophysiological mechanism.