Synergy of sarcopenia and vitamin D deficiency in vertebral osteoporotic fractures in rheumatoid arthritis

Objectives To explore the synergistic effect of vitamin D deficiency and sarcopenia on vertebral osteoporostic fracture (VF) in patients with rheumatoid arthritis (RA). Methods A total of 188 patients with RA and 158 control subjects were enrolled. Bone mineral density (BMD) at the total hip, neck of femur, lumbar vertebra 1-4, and skeletal muscle mass was measured by dual energy X-ray absorptiometry (DXA) and biological electrical impedance, respectively. Serum 25(OH)D was tested by electrochemiluminescence. The prevalence of VF and osteoporosis (OP) were compared between RA and controls. The synergism of sarcopenia and vitamin D deficiency on VF in patients with RA was tested by chi(2) test and logistic regression. Results The prevalence of OP at all measured sites and VF in RA patients were all higher than those in controls (P < 0.0001). The incidence of VF in RA either with sarcopenia or with vitamin D deficiency was higher than for those without sarcopenia or without vitamin D deficiency (chi(2) = 5.069, P = 0.027, chi(2) = 8.822, P = 0.001). Age, disease duration, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), DAS28, health assessment questionnaire (HAQ), Sharp score, and body mass index (BMI) were significantly different between RA with sarcopenia or not (P < 0.05). Logistic regression analysis found that age (OR = 1.095, 95%, CI: 1.044-1.150, P < 0.0001) was a significant risk factor for VF in patients with RA, while high skeletal muscle mass (SMI) (OR = 0.513, 95% CI: 0.327-0.804, P = 0.004) was a protective factor for VF in RA patients. Conclusions VF, sarcopenia, and vitamin D deficiency are common in patients with RA. Sarcopenia and vitamin D deficiency may be risk factors for the incidence of VF in RA patients.