Changes in bone mineral density in premenopausal women with rheumatoid arthritis during a two-year follow-up

To ascertain changes in axial bone mineral in premenopausal women with severe rheumatoid arthritis (RA) treated with and without prednisolone (PRED), we conducted a two-year follow-up study of axial bone mineral density (BMD) and bone mineral content (BMC).

Premenopausal RA women (n=74) attending wards in the Rheumatism Foundation Hospital, Heinola, Finland were consecutively recruited for a follow-up study of BMD. BMD measurements in the lumbar spine and left proximal femur (femoral neck) were performed using dual X-ray absorptiometry at baseline and after two years. BMD is expressed as BMC per projectional area g/cm2. The Larsen score of 0-100 was assessed at the check-ups. Two RA groups were analyzed: patients receiving prednisolone (n=48), RA with PRED group and without prednisolone (n=26), RA without PRED group. The control group (n=43) comprised age-matched, premenopausal healthy women.

The patients in the RA with PRED group had lower BMD values than those in the RA without PRED group at commencement of follow-up. The mean weight-adjusted BMD percentage change in the lumbar spine to two years was -1.5% in the RA with PRED group, +0.6% in the RA without PRED group and -0.6% among the controls; a significant difference (P=0.030) was found between the RA groups. The mean BMC percentage change to two years in the lumbar spine was -2.2% in the RA with PRED-group (P=0.003), +0.0 in the RA without PRED-group and -0.6% in the control group. Accordingly, the mean weight-adjusted BMD percentage change in the femoral neck to two years was -2.6% in the RA with PRED group, +0.4% in the RA without PRED group and -0.9% among the controls; the difference between the RA groups being again significant (P=0.049). The mean BMC percentage change to two years in the femoral neck was -1.9% (P=0.006), -0.4% and -0.8%, respectively. Mean BMD decreased significantly in both lumbar spine (P=0.002) and femoral neck (P<0.001) only in the RA with PRED group. However, in spite of statistical findings above, when BMD is expressed as BMC per projectional area there was no statistically significant difference between the three groups in the change in BMC or projectional area in the lumbar spine or femoral neck. There was no significant correlation between the change in BMD in lumbar spine or femoral neck and the change in Larsen score among the RA groups.

We conclude that according to BMC, premenopausal RA women both with and without prednisolone treatment and controls lost bone statistically similarly. It seems that the role of RA itself in the multifactorial development of axial bone mass during the first decade of severe RA is not the most essential issue. We assume that this role will be less important with better treatment of RA than our patients received. The amount of bone loss during treatment with low-grade prednisolone remains controversial.