Background In ankylosing spondylitis (AS), gender-attributable differences have been reported with respect to clinical and radiographic outcome. However, longitudinal studies exploring gender-attributable differences in the outcome of AS are scarce and/or have limited follow-up.
Objectives To investigate gender-attributable differences regarding clinical outcome (disease activity, physical function and quality of life (QoL)) and radiographic damage in patients with AS over time.
Methods Data from the Outcome in AS International Study were used. Disease activity was assessed by the Bath AS Disease Activity Index (BASDAI), C-reactive protein (CRP), and AS Disease Activity Score with CRP (ASDAS-CRP); physical function by Bath AS Functional Index (BASFI); QoL by the Short Form-36 Physical and Mental Component Summary scores (SF-36PCS and SF-36MCS), ASQoL and EuroQoL; and radiographic damage by the modified Stoke AS Spine Score (mSASSS). Cross-sectional comparative analyses were done at baseline. Next, separate models were created to assess gender-attributable differences on each outcome measure over time using generalized estimating equations. All analyses were performed in the total population and in those patients who completed the total 12 years of follow-up.
Results 216 patients (154 (72.3%) males, mean age 43.6 years (SD 12.7), symptom duration 20.5 years (SD 11.8), mean follow-up duration 8.3 years (SD 4.1)) were included. At baseline, male compared with female patients had lower self-reported disease activity (BASDAI 3.2 vs. 3.9, p=0.03) but more radiographic damage (mSASSS 13.8 vs. 6.5, p=0.02). No significant gender-attributable differences in other clinical parameters were found. In multivariable analysis using separate models, male gender was significantly associated with a better ASQoL (B=-1.18, 95% confidence interval (CI) -2.17 to -0.20, p=0.02), with a better SF-36MCS (B =5.84, 95% CI 2.21 to 9.48, p<0.01) and with a higher mSASSS over time (B=8.24, 95%CI 4.38 to 12.09, p<0.01). Similar results were found for the 12-year completers.
Conclusions In this prospective cohort study, no gender-attributable differences were found for disease activity (measured with ASDAS) or physical function over time. However, male patients had more severe radiographic damage over time. Furthermore, and independently of radiographic damage, male patients had a better QoL over time. It is likely that gender differences in AS are determined by both biological and psychological factors, and that male and female patients differ in the way they cope with pain and disability.
Disclosure of Interest None declared