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.