Comorbidities in Argentine patients with axial spondyloarthritis: Is nephrolithiasis associated with this disease?

Objective: The objective of this study was to compare the frequency of comorbidities among patients with ax-SpA in the general population and to evaluate the impact of these comorbidities on the functional status and quality of life.

Methods: Patients with ax-SpA fulfilling the modified New York 1984 criteria for Ankylosing Spondylitis (AS) and/or Assessment of SpondyloArthritis International Society (ASAS) 2009 criteria for patients with ax-SpA belonging to the ESPAXIA cohort ("Estudio de eSPondiloartritis Axial Irep Argentina") were included. Data regarding sociodemographics, comorbidities, and disease characteristics were recorded. Statistical analysis included descriptive statistics using the student t-test, Chi-square, and Fisher's exact test. Multiple logistic regression analysis was performed. A p value <0.05 was considered significant.

Results: In total, 86 patients were included, 80% were males with a median age of 46 years (interquartile range [IQR]: 32-58) and a median disease duration of 19 years (IQR: 13-31). The most frequent comorbidities reported were hypertension (26.7%), gastritis (25.6%), dyslipidemia (24.4%), gallstone (12.8%), nephrolithiasis (11.6%), anemia (10.5%), hypothyroidism (7%), and type 2 diabetes (6%). The prevalence of these comorbidities in patients with ax-SpA was similar to that observed in the general population, with the exception of a higher frequency of nephrolithiasis among patients with ax-SpA (11.6% in ax-SpA vs 3.96% in the general population). We further categorized the study population into three groups: patients with no comorbidities, those with 1 or 2 comorbidities, and those with ≥3 comorbidities. The presence of ≥3 comorbidities was associated with older age, longer disease duration, worse disease activity, functional status, and quality of life as compared with the patients without comorbidities. In multivariate analysis, older age was the only variable independently associated with the presence of comorbidities.

Conclusion: The frequency of comorbidities in the ax-SpA cohort was high, and the only variable associated with a higher prevalence of comorbidities was older age. Nephrolithiasis was more frequent in the patients with ax-SpA than that reported in the general population.