Patients with rheumatoid arthritis (RA) have been shown to have an increased risk of osteoporosis and fractures. Most studies on RA and osteoporosis are cross-sectional and only a few have investigated changes in bone mineral density (BMD) over time.
The objective of this investigation was to study changes in BMD in men and women with early RA over a period of 10 years.
An inception cohort of consecutive patients with early RA (N=233, symptom duration <12 months), recruited from 1995–2005, was investigated.1,2 Patients were followed according to a structured programme, including dual-energy X-ray absorptiometry (DXA) of the left femoral neck and the lumbar spine (L2–L4) at inclusion and after 2, 5, and 10 years. Z-scores (standard deviations above or below the mean BMD for the given age and sex) were calculated using a cohort of healthy individuals from the same area as the reference population. The mean Z-score over the study period was estimated using mixed linear effect models. Changes in Z-scores between follow-up visits were analysed using the paired T-test. Data are presented as mean values with corresponding 95% confidence intervals (CI).
At inclusion, 220 patients were examined with DXA. The corresponding numbers of patients examined at 2, 5, and 10 years were 196, 173, and 122, respectively. Among those with baseline DXA data, the mean age was 60 years, the mean symptom duration was 7.4 months, and 70% of the population were women. Men were older than women (mean age of 63 versus 59 years, respectively) and more often treated with corticosteroids at inclusion (49% versus 35%, respectively). Most of the patients were on disease-modifying antirheumatic drugs (86% of males and 81% of females). More women were treated for osteoporosis (using bisphosphonates and/or calcium and vitamin D), and 16% of the female participants were on oestrogen at inclusion.
At the femoral neck, the mean Z-score over 10 years was -0.07 (95% CI: -0.22–0.08) in women and -0.33 (95% CI: -0.57–[-0.08]) in men. Men had significantly lower BMD at the femoral neck than expected by age at inclusion. The was no significant change in femoral neck Z-scores over time in men and women. At the lumbar spine, the mean Z-score for women was 0.06 (95% CI: -0.10–0.21) and -0.05 (95% CI: -0.29–0.19) for men. There was a significant increase in Z-scores at the lumbar spine over time in both groups.
In the paired comparisons of BMD at different follow-up visits, Z-scores in the femoral neck decreased significantly from inclusion to the 5-year follow-up visit in men (mean change: -0.23 [95% CI: -0.43–(-0.03)]). After 5 years, no further reduction was seen. Lumbar spine BMD Z-scores increased in both men and women over the study period (mean change: 0.36 [95% CI: 0.21–0.52] in women and 0.47 [95% CI: 0.20–0.74] in men).
In this study of patients with early RA, men had low femoral neck BMD at the start of the study and kept losing bone mass during the first 5 years of follow-up. Lumbar spine BMD Z-scores in both women and men increased significantly over the study period. Potential explanations for the low femoral neck BMD in men include factors that may predispose the patients to both RA and low BMD, such as smoking and low androgen levels.3 The increasing lumbar spine BMD could be due to more extensive antiosteoporotic treatment compared to the reference population, or could be the result of more artefacts, such as extensive aortic calcification or degenerative spinal changes, in patients with RA.