Background Secondary osteoporosis is a well-known comorbidity in rheumatoid arthritis (RA). It is assumed that generalized bone loss is associated with multifactorial causes including systemic inflammation, treatment with steroids, and immobility. Moreover, osteoporosis in RA could add up to more pain and immobility leading to decreased quality of life. However, it is still unclear if RA may affect bone metabolism of vertebra by itself and how bone mineral density (BMD) would change during the time course since the diagnosis of RA.
Objectives To examine lumbar BMD and bone turnover markers before the intervention of treatment for early RA and its changes over 3 years, and to clarify factors contributing to the BMD change.
Methods Ninety three consecutive patients newly diagnosed with RA were enrolled in this study after excluding 6 patients who had been diagnosed with osteoporosis and treated before. Dual-energy X-ray absorptiometry (DEXA) scan was performed at baseline and every one year over 3 years. Serum and urine bone turnover markers including collagen type 1 cross-linked N-telopeptide (NTx), and deoxypyridinoline (DPD), and osteocalcin (OC) were measured at baseline and every 6 months. Disease activity in RA was calculated using DAS28. Statistical analysis was performed by paired or unpaired t-test.
Results Baseline characteristics of 93 patients are as follows: mean age was 59, 78 (84%) were female, mean duration from the onset of symptom to the diagnosis of RA was 10 months, 69 (74%) were positive for anti-CCP antibody, and mean DAS28 was 4.6. There were only 6 patients who were treated with predonisolon (PSL) during this 3-year observation period, and the dose of PSL was within 5 mg/day in all of them. At baseline, mean BMD, T-score and Z-score were within normal range (1.12 mg/m3, -0.1 and 0.9, respectively). However, the mean serum NTx, urine DPD, and serum OC were 19.1 nmolBCE/l, 8.6 nmol/nmol·Cr, and 5.8 nmol/l·s, respectively, indicating general bone absorption was increased at the diagnosis of RA. Moreover, in patients with anti-CCP positive or whose hand MRI at baseline showed bone erosions and/or bone oedema, mean BMD was significantly less than those without (p<0.05 for both). At 36 months, BMD was decreased to 1.11 (-1.3%) that was not significant (p=0.09). The decrease in BMD was significant in patients with anti-CCP positive or whose hand MRI at baseline showed bone erosions and/or bone oedema (1.12 to 1.10, p=0.03, 1.11 to 1.08, p=0.002) while not significant in patients those without (1.14 to 1.15, p=0.60, 1.14 to 1.14, p=0.66) (Figure). The changes in BMD over 3 years were not correlated with DAS28 at baseline or mean DAS28 over 3 years. NTx, DPD, and OC were 18.8 (p=0.69), 6.1 (p=0.001), and 6.1 (p=0.31), respectively, suggesting the improvement of high bone absorption after the treatment of RA.
Conclusions Patients with RA were not complicated with osteoporosis at the time of diagnosis, but bone turn absorption was elevated. Patients with anti-CCP or bone erosion/oedema in hand MRI at baseline are disposed toward decrease in BMD over 3 years.
Disclosure of Interest None declared