The Effects of Sex and Estrogen on Radiographic Progression of Ankylosing Spondylitis in Korean Patients

Objective. Ankylosing spondylitis (AS) is a chronic inflammatory disease with obvious male preponderance. Males show more severe radiographic manifestations compared with females. This study aimed to evaluate the effects of sex and estrogen on the radiographic progression of AS. Methods. A total of 101 patients with AS were included in this study. All of the radiographs were scored using the modified Stoke AS Spine Score (mSASSS). Serum levels of 17β-estradiol (E2), dickkopf-1 (Dkk1), and leptin were detected by enzyme-linked immunosorbent assay. The generalized estimating equations model was used to evaluate factors associated with spinal radiographic progression. Results. The mean age at disease onset was 27.3±10.7 years, and 16 patients (15.8%) were female. In the multivariable analysis, body mass index (β-coefficient=0.12; p=0.047) and levels of Dkk1 (β-coefficient=−0.11; p＜0.001), and female (β-coefficient=−1.40; p=0.001) were associated with radiographic progression. Among male patients with AS, baseline C-reactive protein (β=0.11; p=0.005) and mSASSS (β=0.21; p=0.030) were also associated with radiographic progression. E2 and leptin levels were not significantly related to the radiographic progression. Conclusion. Although female patients were associated with less radiographic progression in AS, there was no significant relationship between serum estrogen level and radiographic progression. Results of current study suggests that genetic factors or other environmental factors associated with female may influence radiographic progression in patients with AS.