Assessment of fracture risk in patients with axial spondyloarthritis: a case-control study using the fifth Korean National Health and Nutrition Examination Survey (KNHANES V)

Objectives: Axial spondyloarthritis (axSpA) is associated with low bone mineral density (BMD) and fractures, although the true fracture risk is unknown. The present study examined BMD and estimated the 10-year fracture risk in axSpA patients and matched controls and identified factors associated with a high fracture risk.Method: In total, 240 axSpA patients and 1200 healthy controls from the fifth Korean National Health and Nutrition Examination Survey (KNHANES V), matched using propensity scores, were included. Dual-energy X-ray absorptiometry (DXA) was used to measure lumbar spine and right femur BMD. Ten-year risks of major osteoporotic and hip fractures were calculated using the Fracture Risk Assessment Tool (FRAX) in subjects aged 40years. Multivariate linear regression models were used to explore factors associated with the 10-year fracture risk in axSpA patients.Results: Hip and lumbar spine BMDs were lower in axSpA patients than in matched controls. Osteoporosis was present in 17% of axSpA patients and 3% of controls (p<0.001). Low BMD was present in 22% of axSpA patients and 4% of controls aged <50years (p<0.001). Ten-year major osteoporotic and hip fracture risks were significantly higher among axSpA patients. High 10-year fracture risk was observed in 10% of axSpA patients and 1.7% of controls (p=0.003). The severity of sacroiliitis was independently associated with both major osteoporotic and hip fracture risks (p=0.006 and 0.026, respectively).Conclusions: Patients with axSpA presented more frequently with low BMD and a higher calculated 10-year fracture risk than matched individuals. The severity of sacroiliitis was independently associated with a high 10-year fracture risk in axSpA patients.