Correspondence on “Patients with ankylosing spondylitis have high risk of irritable bowel syndrome.”

KEYWORDS:

• Ankylosing spondylitis
• irritable bowel syndrome
• epidemiology

To the editor

We read with great interest the study by Feng et al. [1] investigating the potential effect of ankylosing spondylitis (AS) on the subsequent long-term risk of irritable bowel syndrome (IBS). Feng et al. [1] provided valuable and novel clinical information and indicated that after full adjustments, the study group (N = 3,516) developed 167 (4.75%) cases of IBS with a higher risk of new-onset AS (aHR, 2.50; 95% CI, 1.91–3.29) than the controls. However, we have several concerns about the methodology and residual confounders.

First, the study and control group posed similar distribution of baseline characteristics after propensity score matching However, the authors used 1:1 ratio for both groups during the matching process instead of commonly used 1:4 ratio for a better statistic power in other epidemiological studies [2–4]. We suggest the authors consider rematching both groups to test the robustness of their findings.

IBS typically presents as a chronic and insidious condition, with severe discomfort being relatively uncommon among those affected. To reduce the potential fo protopathic bias, we recommend that the authors consider excluding cases of IBS that occurred in close proximity to the index date of AS diagnosis.

In conclusion, we are convinced by the authors’ conclusions. They assess the association of potential confounders (i.e., age, gender, and comorbidities) with IBS after having a diagnosis of AS. Since all P values for interaction are nonsignificant, the possible effect of AS on IBS seems to be universal. Although the causal relationship of AS to IBS requires more research to reach a firm verdict, we thank Feng et al. for their article and look forward to their response.

Declaration of financial/other relationships

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties. Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Acknowledgments

None stated.

Additional information

Funding

This paper was not funded.