Forearm bone mineral density in postmenopausal women with rheumatoid arthritis

Osteoporosis in cases of rheumatoid arthritis (RA) is multifactorial, and the pathogenesis of bone loss induced by RA in postmenopausal women is not fully understood. The purpose of the present study was to determine the factors that affect forearm bone mineral density (BMD) in postmenopausal women with RA. In total, 839 postmenopausal women aged 46-90 years, were enrolled in the study; 470 patients with RA and 369 healthy controls (CON). Forearm (distal radius) BMD, measured by DXA using a DTX-200 (Osteometer, MediTech, CA, USA), was significantly lower in the RA group than in the CON group (P < 0.0001), even when adjusted for age, height, body weight, body mass index, and years since menopause (YSM) (P < 0.01). On multiple regression analysis, in the CON group, age and YSM were significantly correlated with BMD (P < 0.01 and P < 0.05, respectively). On the other hand, in the RA group, in addition to YSM, anatomic grade in the wrist, modified health assessment questionnaire (HAQ) score for the upper extremities, and erythrocyte sedimentation rate were each significantly correlated with BMD (P < 0.0001, P < 0.001, P < 0.0001, and P < 0.001, respectively), whereas functional class, duration of disease, dose of prednisolone used, modified HAQ score for the lower extremities, and the levels of c-reactive protein and rheumatoid factor were not. The present study with a large number of subjects shows that in addition to YSM, disuse (anatomic grade) of the wrist, arm function, and disease activity appear to be significant determinants of forearm BMD in postmenopausal women with RA.