Patterns of comorbidity and disease characteristics among patients with ankylosing spondylitis—a cross-sectional study

The knowledge of the development of comorbidities in patients with ankylosing spondylitis (AS) is limited. The aim of this study was to analyse associations between AS disease characteristics and comorbidity and to evaluate patterns of comorbidities in patients with AS. Patients with AS, fulfilling the modified New York Criteria, were identified (n = 346, mean age 56 ± 15 years, 75% men, 99% HLA B27 positive). Through a review of the patient records, data on disease activity parameters, laboratory results, disease manifestations, and diagnoses of any clinically significant comorbidity was obtained. Four categories of comorbidities of interest were identified: A. arrhythmias, conduction disorders, and valvular heart disease; B. atherosclerosis and atherosclerotic CVD; C. spinal and non-spinal fractures; and D. obstructive sleep apnoea syndrome. Associations between AS disease characteristics and comorbidities in categories were assessed in logistic regression models. Differences in proportions of comorbidities was analysed using two-sided chi-square. Age was associated with all four categories of comorbidities, and male sex with arrhythmias, conduction disorders, valvular heart disease, and obstructive sleep apnoea syndrome. Early disease onset and long disease duration, respectively, were associated with arrhythmias, conduction disorders, and valvular heart disease. Obstructive sleep apnoea syndrome was associated with features of the metabolic syndrome. Patients with atherosclerotic cardiovascular disease had an increased risk of most other comorbidities, similar to, but more pronounced than patients with arrhythmias, conduction disorders and valvular heart disease. Comorbid conditions motivate clinical awareness among patients with AS. Longitudinal studies are needed to establish preventive measures.