The Frequency of Osteosarcopenia and Its Relationship With Demographic and Clinical Factors in Axial Spondyloarthritis

Ankylosing Spondylitis (AS) is a chronic inflammatory disease of unknown etiology that affects the spine, sacroiliac joints, entheses regions, and sometimes peripheral joints. Its typical findings include inflammatory back pain, limited spinal mobility, and radiographic sacroiliitis. The term axial spondyloarthritis (AxSpA) describes a chronic inflammatory disease affecting the axial skeleton, including the spine and sacroiliac joints. It encompasses both patients with definite AS diagnosis with radiographic (X-ray) sacroiliitis, and patients with non-radiographic AxSpA whose sacroiliitis detected by MRI. Osteoporosis is among the clinical findings of AS. Similarly, sarcopenia may develop in AS patients due to both inflammation and immobilization. Osteosarcopenia is a clinical syndrome that includes both osteoporosis and sarcopenia. Osteosarcopenia may be a significant cause of morbidity and mortality in AxSpA patients.

This study aims to determine the frequency of osteosarcopenia in patients with AxSpA and to investigate its relationship with demographic and various clinical parameters. To determine the presence of osteoporosis, bone mineral density (BMD) measurement will be performed using Dual-energy X-ray absorptiometry (DXA). WHO definition for the diagnosis of osteoporosis will be used. A T score at or below -2.5 at the lumbal and/or hip region is defined as osteoporosis. Subsequently, to determine the presence of sarcopenia, patients will be assessed according to the European Working Group on Sarcopenia in Older People (EWGSOP2) algorithm through measurements of muscle strength, muscle mass quantity or quality, and physical performance. Skeletal muscle mass or quality will be measured by appendicular skeletal muscle mass (ASM) using both DXA, and bioelectrical impedance analysis (BIA). Skeletal muscle strength will be measured by grip strength and physical performance by gait speed. EWGSOP2 cut-off points will be used for low muscle strength (grip strength), low muscle quantity (ASM/height2) and low physical performance (gait speed). Then the sarcopenia diagnosis (probable, confirmed, severe) will be made according to the 2018 operational definition of sarcopenia by EWGSOP2. A healthy control group with similar age and gender distribution will be recruited to evaluate osteosarcopenia and compare with the patient group. After determining the presence of osteosarcopenia in AxSpA, the relationship between osteosarcopenia (sarcopenia and osteoporosis) and demographic/clinical parameters including age, gender, physical activity, disease duration, medications used (biological vs. non-biological), disease activity, spinal mobility, radiological involvement, and functional status will be investigated.

There has been no prior study on investigating osteosarcopenia in AxSpA. We expect a higher frequency osteosarcopenia in the AxSpA group compared to the control group. Additionally, the relationship between osteosarcopenia and clinical parameters will be demonstrated, thus increasing the attention and awareness of patients at high risk for developing osteosarcopenia, and facilitating early steps in treatment.