ObjectivesTo describe and compare the prevalence of comorbidities in female and male patients with spondyloarthritis (SpA) and to assess whether comorbidities had a different impact on disease outcomes in male and female patients.MethodsThis is a post hoc analysis of the COMOrbidities in SPondyloArthritis study. Differences in comorbidities regarding sex were assessed using logistic regression models. Comorbidities were evaluated for their impact on disease outcomes (Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Ankylosing Spondylitis Disease Activity Score (ASDAS), Bath Ankylosing Spondylitis Functional Index, European health-related quality of life questionnaire) with linear models, which included sex and comorbidity as explanatory variables and their interaction. Age and treatment with biological synthetic disease-modifying antirheumatic drugs were included as confounders.ResultsWe included 3982 patients with SpA (65% male, mean age 43.6 years). Male and female patients with SpA exhibited similar comorbidity profiles, except for a low prevalence of fibromyalgia in males and a higher prevalence of certain cardiovascular risk factors in males (hypertension, dyslipidaemia, renal impairment and ischaemic heart disease). Comorbidities, especially fibromyalgia, correlated with higher disease activity, decreased physical function and reduced health-related quality of life in both sexes. Some comorbidities exhibited sex-specific associations with disease outcomes. Peptic ulcers and high waist circumference had a greater impact on disease activity in females (with a higher impact in BASDAI than in ASDAS). In contrast, osteoporosis had a more pronounced effect on physical function in male patients.ConclusionsComorbidities exert distinct influences on disease activity, physical function and health-related quality of life in male and female patients with SpA. Understanding these sex-specific effects is crucial for improving SpA management, emphasising the importance of assessing disease activity using ASDAS when comorbidities are present to mitigate sex-related disparities in disease assessment.