Gender-attributable differences in outcome of ankylosing spondylitis: long-term results from the Outcome in Ankylosing Spondylitis International Study

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 BASDAI, ASDAS and CRP; physical function by BASFI; QoL by the Short Form-36, Ankylosing Spondylitis Quality of Life (ASQoL) score and European Quality Of Life scale; 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 time-adjusted generalized estimating equations.

Results. A total of 216 patients [154 (72.3%) males, mean age 43.6 years (S.D. 12.7), symptom duration 20.5 years (s.o. 11.8), mean follow-up duration 8.3 years (S.D. 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, male gender was significantly associated with a better ASQoL (B = -1.18, 95% CI: -2.17, -0.20, P=0.02), and in a separate model with a higher mSASSS over time (B = 8.24, 95% CI: 4.38, 12.09, P <0.01).

Conclusion. In this prospective cohort study, no gender-attributable differences in disease activity or physical function over time were found. However, radiographic damage was more severe in males. Furthermore, males had a better QoL over time.