Background/Purpose: 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 have limited follow-up. The aim of the present study was to investigate gender-attributable differences with respect to clinical outcomes (disease activity, function and quality of life (QoL)) and radiographic damage in patients with AS over time.

Methods: Clinical and radiological data from patients included in the Outcome in AS International Study (OASIS) were used. Disease activity was assessed by the Bath AS Disease Activity Index (BASDAI), the AS Disease Activity Score (ASDAS), and C-reactive protein (CRP); physical function by Bath AS Functional Index (BASFI); QoL by the Short Form-36 (SF-36), ASQoL and EuroQoL; radiographic damage by the modified Stoke AS Spine Score (mSASSS). First, cross-sectional comparative analyses were done at baseline. Second, separate models were created to assess gender-attributable differences on each outcome measure over time using time-adjusted generalized estimation equations (GEE). 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%) men, 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 differences in other clinical parameters between gender were found at baseline. In univariable analysis, a significant association between male gender and better QoL (lower ASQoL and higher EuroQoL), and between male gender and more radiographic damage (higher mSASSS) over time was found.

Also in multivariable analysis, male gender was, compared with female gender, significantly associated with a better ASQoL (B= -1.10, 95%CI -2.11 to -0.09, p=0.03), and in a separate multivariable analysis also with higher mSASSS over time (B=8.52, 95%CI 4.55 to 12.50, p<0.01). Similar results were found for the 12-year completers.

Conclusion: In this longstanding observational cohort study in patients with AS, no gender-attributable differences in disease activity and function over time were found. However, male gender, compared with female gender, was found to be associated with more radiographic damage, but also better QoL. 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.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/gender-attributable-differences-in-outcome-of-ankylosing-spondylitis-long-term-results-from-the-outcome-in-ankylosing-spondylitis-international-study/