Background/Purpose: Patients with rheumatoid arthritis (RA) develop osteoporosis more frequently than healthy individuals. Bone resorption and formation are respectively increased and inhibited in patients with RA, and steroids negatively affect bone metabolism in both patients with RA and healthy individuals. The effect of reducing the steroid dose on bone metabolic markers in patients with RA has remained unknown. We aimed to investigate the factors influenced for bone metabolic markers in RA patients using multivariate analysis technique.

Methods: We started the 10-year prospective cohort TOMORROW (TOtal Management Of Risk factors in Rheumatoid arthritis patients to lOWer morbidity and mortality clinical trial (registration number, UMIN000003876)) in 2010. We compared changes in urinary crosslinked N-telopeptide of type I collagen (NTx) and serum osteocalcin (OC), which are markers of bone resorption and formation, respectively, in a total of 404 age- and sex-matched RA patients and volunteers between 2010 and 2011 (delta NTx = NTx during 2011 – NTx during 2010; delta OC = OC during 2011 – OC during 2010). We also investigated the factors influenced for delta NTx and delta OC in RA patients using multivariate analysis technique.

Results: Baseline demographics were showed in Table 1. There were no significant differences in all parameters between groups. The delta NTx values were significantly lower in the patients than in the volunteers (-0.51 ± 29.4 vs. 7.41 ± 18.7 nmol; p = 0.0013), whereas the delta OC values were significantly higher in the patients (0.94 ± 2.47 vs. 0.37 ± 1.62; p = 0.0065). The change of prednisolone (PSL) dosage negatively correlated with delta OC (b = -0.229, p = 0.001), whereas change of disease activity score (DAS28), bisphosphonate therapy, and period of biologics therapy did not significantly correlate with delta OC (Table 2).

Conclusion: A decrease in the dose of PSL respectively decreased and increased markers of bone resorption and formation among patients with RA. That is, bone metabolic makers were improved. However, disease activity, bisphosphonate therapy, and period of biologics therapy did not influence for bone metabolic makers. Thus, bone metabolic markers might degenerate even when disease activity is under good control. Decreasing the PSL dosage is important for bone metabolism in patients with RA.

Table 1: Baseline demographics

BMI: body mass index

Table 2: The factors influenced for delta OC in RA patients

PSL: prednisolone, DAS: disease activity score