Risk of ankylosing spondylitis following chronic tonsillitis and adenoiditis: a retrospective cohort study utilizing TriNetX global collaborative network

Objective: To assess the incidence rate and risk of ankylosing spondylitis (AS) in patients with chronic tonsillitis and adenoiditis compared with those without chronic tonsillitis and adenoiditis. Methods: All patients with chronic tonsillitis and adenoiditis (n = 104,956) in the TriNetX (2016–2023) were individually matched up with control subjects without chronic tonsillitis and adenoiditis by age and sex (n = 104,956). All of the patients were tracked until an AS event was noted. Cox proportional hazards regression was used to calculate the HRs for the development of AS, adjusting for age, sex, urbanization, lifestyle, medications, and comorbidities. The Kaplan-Meier method was used to plot the cumulative incidence curves. Subgroup analyses examined the association between chronic tonsillitis and adenoiditis and AS in subgroups stratified by age, sex, and, race. To ensure the robustness of the findings, in this sensitivity analysis, this study incorporated five different negative outcome controls. Results: The chronic cohort had a 1.41(95%C.I. = 1.11–1.80) times higher risk of AS than that of the non-chronic tonsillitis and adenoiditis cohort after adjusting for age, sex, race, BMI, socioeconomic status, lifestyle, medical utilization, comorbidities, and medications. Moreover, the cumulative incidence curves plotted by the Kaplan-Meier method revealed that after 7 follow-up years, the chronic tonsillitis and adenoiditis cohort displayed a higher cumulative incidence of AS than that of the non-chronic tonsillitis and adenoiditis cohort (Log-rank test p = 0.005). Additionally, subgroup analyses indicated stronger associations in females (HR = 1.36, 95% CI: 1.02–1.80) and individuals aged 18–64 years (HR = 1.39, 95% CI: 1.08–1.78). Sensitivity analyses using negative outcome controls (e.g., burns, cancer) confirmed specificity of the association. Conclusions: Our study revealed that patients with chronic tonsillitis and adenoiditis had a higher risk of developing AS compared with non-chronic tonsillitis and adenoiditis patients, especially in females and those below 65 years old. These findings highlight the potential role of chronic upper airway inflammation in AS pathogenesis and warrant further investigations.