Background: Fatigue is a common and disabling symptom in axial spondyloarthritis (axSpA), yet its magnitude relative to the general population and potential sex-specific differences remain insufficiently characterized, particularly in older adults. We therefore aimed to assess fatigue in adults aged ≥ 50 years with axSpA, using the Functional Assessment of Chronic Illness Therapy–Fatigue (FACIT-F) scale, to compare fatigue levels with age- and sex-matched controls, and to explore sex-specific differences and clinical factors associated with fatigue. Methods: We conducted an observational case–control study including consecutive patients with axSpA aged ≥ 50 years and control subjects frequency-matched by age and sex. Fatigue was assessed using the FACIT-F, and clinically relevant fatigue was defined as a FACIT-F score < 40. Case–control comparisons were stratified by sex, and sex-stratified multivariable linear regression models were applied. Results: The study included 173 patients with axSpA (120 men, 53 women; mean age: 64.2 years) and 383 controls. Clinically relevant fatigue was more frequent in women than in men (84.9% vs. 50.0%; p < 0.001). Women reported more severe fatigue than men (FACIT-F: 29.4 ± 10.4 vs. 37.4 ± 10.2; p < 0.001). In case–control comparisons, fatigue was greater in patients than in controls in both sexes, with descriptively larger differences among women. In sex-stratified multivariable analyses, the ASAS Health Index (ASAS-HI) was independently associated with fatigue in both men and women. In reduced models including age, BASDAI, and ASAS-HI, ASAS-HI remained independently associated with FACIT-F in both men (β: −1.74, 95% CI: −2.08 to −1.41) and women (β: −1.80, 95% CI: −2.35 to −1.26; p < 0.001 for both). BASDAI showed an additional independent association in women (β: −1.19, 95%: CI −2.09 to −0.30; p = 0.010), but not in men. Conclusions: Fatigue is highly prevalent and clinically relevant in adults aged ≥50 years with axSpA, with a clear sex-specific pattern. Women experience a greater fatigue burden, and comparisons with controls suggest a larger excess among women. Fatigue represents an important dimension of disease burden in axSpA, with stronger associations with overall health status than with conventional inflammatory measures.
Nolla et al. (Tue,) studied this question.