Synergistic effect of sarcopenia and poor balance on osteoporotic vertebral fracture in Chinese patients with rheumatoid arthritis.

OBJECTIVES: This study aimed to investigate the synergistic effect of sarcopenia and poor balance on osteoporotic vertebral fracture (VOPF) in Chinese patients with rheumatoid arthritis (RA). METHODS: A total of 238 RA patients and 158 normal subjects were enrolled in the case-control study. Poor balance capability (Berg balance scale (BBS) score < 40) and sarcopenia (skeletal muscle mass index (SMI) <7.0 (male)/5.7 (female)) between RA patients and normal subjects were compared. Associations of poor balance capability or sarcopenia with disease activity, structural damage, and joint function in different groups were also investigated. RESULTS: The incidence of sarcopenia in RA was 58.4%, significantly higher than that in controls (P<0.0001). Moreover, the percentages of low balance capacity (BBS<40) in RA were 43.7%, which was higher than that in controls (P<0.0001). The prevalence of VOPF in the case group was 19.3%, which was higher than that in the controls (P<0.0001). In the RA group, compared to RA patients without VOPF, RA patients with VOPF had higher percentages of poor balance and sarcopenia (P<0.05). Compared with RA patients without sarcopenia or good balance, RA patients with sarcopenia or poor balance had a higher incidence of VOPF, higher disease activity, severer structural damage, and worse joint function (P<0.05). The incidence of VOPF in patients combined with good balance and non-sarcopenia (4.8%) was significantly lower than that in patients combined with poor balance and sarcopenia (38.2%) (P<0.0001). Logistic regression indicated that higher SMI and higher BBS scores were protective factors for VOPF in RA patients, while age was a risk factor for VOPF in RA patients (P<0.0001). CONCLUSION: Sarcopenia and poor balance are popular in Chinese patients with RA, and they are associated with disease activity and structural damage. There is a synergistic effect of sarcopenia and poor balance on VOPF in RA. Key Points • Sarcopenia and balance capability were popular (about a half) in patients with RA. • Sarcopenia and poor balance had a synergistic effect on VOPF in RA.