The risk factors of bone mineral density abnormality in patients with ankylosing spondylitis

English Keywords:Ankylosing spondylitis  Bone mineral density  Osteoporosis  Influence factors

English Abstract:

  【Abstract】 Objectives: To explore the risk factors for bone mineral density(BMD) abnormality in patients with ankylosing spondylitis(AS). Methods: A retrospective study of patients with AS who came to our hospital from May 2018 to May 2019 were involved. Data of age, duration of disease, erythrocyte sedimentation rate (ESR), C-reactive protein(CRP) and physical examinations such as wall distance and thoracic activity was evaluated. Healthy people in the same period were included to control group. Dual-energy X-ray absorptiometry(DXA) was used to record bone mineral density of femoral neck and lumbar spine in both AS group and control group. Two independent samples t-test were conducted to compare the differences between both groups. And Pearson correlation analysis was used to explore the potential influencing factors of abnormal BMD in patients with AS. Cox regression was used to analyze the risk factors of abnormal bone mineral density in AS. Results: A total of 23 male AS patients and 20 age-matched healthy adult male controls were included in this study. The mean age of AS group was 36.57±5.93 years, and 38.85±4.03 years of control group(P>0.05). The average duration of the case group was 5(3, 7) years. The BMD of the femoral neck(0.86±0.17), greater trochanter(0.85±0.12), lumbar spine(0.90±0.10) and total hip joints(0.88±0.16) in case group was statistically significant lower than that of the control group(0.98±0.21, 0.94±0.15, 1.16±0.14 and 0.99±0.19 respetively, P<0.05). In AS group, the abnormal BMD of femoral neck and total hip joints was negatively correlated with disease duration, age, inflammation index, pillow wall distance and finger distance, and positively correlated with thoracic activity and spinal activity(P<0.05). Abnormal BMD of the greater trochanter was negatively correlated with age, ESR, CRO, and occipital wall distance, and positively correlated with thoracic activity and spinal activity(P<0.05). Univariate analysis found that disease course, ESR, CRP, finger distance, and thoracic activity were related to AS bone abnormalities(P<0.05). Multiple linear regression analysis showed that disease course(b=1.33，P=0.01) and ESR(b=0.75，P=0.04) were independent risk factors for AS bone density abnormalities. Conclusions: The BMD of the femoral neck, greater trochanter, lumbar spine and total hip joints in patients with AS is lower than that of healthy population of the same age. The abnormal BMD of the femoral neck and total hip joints were associated with the course of disease, age, inflammation index, pillow wall distance and fingertips distance, thoracic activity, and spinal activity. The course of disease and ESR are independent risk factors for abnormal bone mineral density in AS.