Background/Purpose:

Sex effects have been noted in axial spondyloarthritis (AS) however controversy still exists regarding male and female clinical manifestations of AS. This includes uncertainty regarding pattern of spinal disease, peripheral joint involvement, and clinical burden of disease. Prior studies have often been limited by numbers and lack of contemporaneous comparators.  In this study we examine sex effects on a longitudinal observation cohort of AS.

Methods:

A systematic review of 950 AS patients (671 male and 279 female) followed in a longitudinal clinic which entails regular clinic visits using a standardized protocol. Patients were stratified by sex. Descriptive characteristics using means (sd) and frequencies (%) can be seen in Table 1. Tests were used to compare continuous variables and Chi-Squared tests for categorical variables. P-value <0.05 was used to define statistical significance.

Results:

We observed that age of onset of back pain was higher in females, and that there was a significant longer delay in diagnosis in females. CRP levels were lower among female patients. This finding parallels previous reports of lower CRP among female with non-radiographic axSpA. We noticed no difference between both sex in terms of affected joints, nor with respect to key extra-articular manifestations (iritis, psoriasis, inflammatory bowel disease). Significant differences in BASMI indicate less impairment of spinal mobility, which may reflect both lower levels of CRP and lower rates of smoking, both of which have been previously associated with structural progression of AS. The use of biologic agents as a surrogate marker of symptomatic burden of disease did not differ between females and males but comparative ASQOL scores reflected greater impact on quality of life in females.

Conclusion:

Our large cohort documents later onset of AS symptoms and longer delay in diagnosis in female AS patients compared with males. Difference in inflammatory markers might be a reflection of different disease pathogenesis but environmental factors such as smoking also contribute to the difference in clinical expression of the disease.  

TABLE 1: Comparison of Baseline Demographic and Disease Characteristics by Sex (n=950)